geological information series — an explanatory …...1 east yilgarn 1:100 000 geological...

REPORT95

by P. B. Groenewald and A. Riganti

Geological Survey of Western AustraliaGeological Survey of Western Australia

Industry and ResourcesIndustry and ResourcesDepartment ofDepartment of

EAST YILGARN 1:100 000GEOLOGICAL INFORMATION SERIES

— AN EXPLANATORY NOTE

MOUNTALEXANDER

COSMONEWBERY

DEPOTSPRINGS

MOUNTVARDEN

MOUNTMASON

MOUNTBELCHES

SG 51-9WILUNA

DUKETON

LEONORA LAVERTON

MENZIES EDJUDINA

KALGOORLIE KURNALPI

BOORABBIN WIDGIEMOOLTHA

NORSEMAN

SIR SAMUEL

SI 51-2

SH 51-1

SH 51-9

SH 51-13 SH 51-14

SH 51-10

SH 51-6

SH 51-2

SG 51-13 SG 51-14

SH 51-5

LAKE LEFROY

3234

COWAN

CUNYU2945

MILLROSE3045

BALLIMORE3145

SANDALWOOD31443044

LAKE VIOLETWILUNA2944

MOUNT KEITH DE LA POER

SIR SAMUEL

LAKE CAREY MOUNT CELIA

3242BANJAWARN

BOYCE32382938

2939

2940

2941

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3036

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3135

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MULLINE

MUNJEROO

YEELIRRIE

DUNNSVILLE

DAVYHURST

RIVERINA

BALLARD

WILBAH

WILDARA

YILMIA

KALGOORLIE

BARDOC

MENZIES

MELITA

LEONORA

WEEBO

DARLOT

WANGGANNOO

NORSEMAN

KANOWNA

GINDALBIE

YERILLA

MINERIE

NAMBI

TATE

KURNALPI

MULGABBIE

EDJUDINA

LAVERTON

DUKETON

URAREY

PINJIN

YABBOO

BURTVILLE

McMILLAN

3335

3336 3436ROE

GEOLOGICAL SURVEY OF WESTERN AUSTRALIA

REPORT 95

EAST YILGARN 1:100 000GEOLOGICAL INFORMATION SERIES— AN EXPLANATORY NOTE

byP. B. Groenewald and A. Riganti

Perth 2004

MINISTER FOR STATE DEVELOPMENTHon. Clive Brown MLA

DIRECTOR GENERAL, DEPARTMENT OF INDUSTRY AND RESOURCESJim Limerick

DIRECTOR, GEOLOGICAL SURVEY OF WESTERN AUSTRALIATim Griffi n

REFERENCEThe recommended reference for this publication is:GROENEWALD, P. B., and RIGANTI, A., 2004, East Yilgarn 1:100 000 Geological Information Series — an explanatory note:

Western Australia Geological Survey, Report 95, 58p.

National Library of AustraliaCataloguing-in-publication entry

Groenewald, PeterEast Yilgarn : 1:100 000 geological information series : an explanatory note.

Bibliography.ISBN 0 7307 8974 8.

1. Geology — Western Australia — Eastern Goldfi elds — Databases. 2. Geological mapping — Western Australia — Eastern Goldfi elds — Databases. I. Riganti, A. II. Geological Survey of Western Australia. III. Title. (Series: Report (Geological Survey of Western Australia); 95).

559.416

ISSN 0508–4741

Grid references in this publication refer to the Geocentric Datum of Australia 1994 (GDA94). Locations mentioned in the text are referenced using Map Grid Australia (MGA) coordinates, Zone 51. All locations are quoted to at least the nearest 100 m.

Copy editor: D. P. Reddy Cartography: T. PizziDesktop publishing: K. S. Noonan

Published 2004 by Geological Survey of Western AustraliaThis Report is published in digital format (PDF) as part of a digital dataset and is available online at www.doir.wa.gov.au/gswa/onlinepublications. Laser-printed copies can be ordered from the Information Centrefor the cost of printing and binding.

Further details of geological publications and maps produced by the Geological Survey of Western Australia are available from:Information CentreDepartment of Industry and Resources100 Plain StreetEAST PERTH, WESTERN AUSTRALIA 6004Telephone: +61 8 9222 3459 Facsimile: +61 8 9222 3444www.doir.wa.gov.au/gswa/onlinepublications

Cover photograph:Location of the East Yilgarn 1:100 000 Geological Information Series area, showing map sheets.

iii

Contents

Abstract ..................................................................................................................................................................1Introduction ............................................................................................................................................................1

Location, access, and physiography ................................................................................................................5The database ....................................................................................................................................................5Layers ..............................................................................................................................................................5

Geology ....................................................................................................................................................5Subsurface observations ...........................................................................................................................5Regional interpreted bedrock geology .....................................................................................................6Aeromagnetic data ...................................................................................................................................6Aeromagnetic interpretation ....................................................................................................................6Landsat 7 TM ...........................................................................................................................................6WAMIN ....................................................................................................................................................6MINEDEX ...............................................................................................................................................6TENGRAPH ............................................................................................................................................6

Geological setting of the Eastern Goldfi elds region ..............................................................................................6Extent of the Eastern Goldfi elds Granite–Greenstone Terrane .......................................................................7Tectono-stratigraphy of the Eastern Goldfi elds Granite–Greenstone Terrane ................................................7

Kalgoorlie terrane ....................................................................................................................................9Gindalbie terrane ......................................................................................................................................9Kurnalpi terrane .....................................................................................................................................10Laverton terrane .....................................................................................................................................10Edjudina terrane .....................................................................................................................................11Norseman terrane ...................................................................................................................................11

Tectono-stratigraphy of the Southern Cross Granite–Greenstone Terrane ...................................................11Illaara greenstone belt ............................................................................................................................11Mount Ida greenstone belt .....................................................................................................................11

Granites and granitic gneisses .......................................................................................................................11Deformational history ...................................................................................................................................13Tectonic settings and models ........................................................................................................................15

Archaean geology .................................................................................................................................................15Archaean rock types ......................................................................................................................................15

Ultramafi c volcanic and subvolcanic rocks ............................................................................................15Mafi c volcanic and subvolcanic rocks ...................................................................................................16Mafi c volcanic rocks — named .............................................................................................................18Felsic volcanic, volcaniclastic, and subvolcanic rocks ..........................................................................18Other volcanic and volcaniclastic rocks .................................................................................................19Chemical sedimentary rocks ..................................................................................................................19Clastic sedimentary rocks ......................................................................................................................20Sedimentary formations .........................................................................................................................21Mafi c intrusive rocks ..............................................................................................................................21Mafi c intrusive rocks — named .............................................................................................................22Layered mafi c to ultramafi c intrusions — named ..................................................................................22Granitic rocks .........................................................................................................................................23Granitic rocks and granitic suites — named ..........................................................................................24Mafi c meta-igneous rocks ......................................................................................................................25Felsic meta-igneous rocks ......................................................................................................................25Metasomatic rocks .................................................................................................................................25Metamorphic rock — protolith unknown ..............................................................................................25

Dykes and veins, unassigned age .........................................................................................................................26Proterozoic geology .............................................................................................................................................26

Mafi c and ultramafi c dykes ...........................................................................................................................26Mafi c and ultramafi c dykes — named ..........................................................................................................26Felsic dykes ...................................................................................................................................................26Yerrida and Earaheedy Basins .......................................................................................................................26

Yerrida Basin ..........................................................................................................................................26Windplain Subgroup — Juderina Formation ..................................................................................26Mooloogool Subgroup — Killara Formation .................................................................................27

Earaheedy Basin .....................................................................................................................................27Proterozoic sedimentary rocks of fl uvial origin ............................................................................................27

Permian geology ...................................................................................................................................................27Cainozoic geology ................................................................................................................................................28

Eucla Basin, Eundynie Group .......................................................................................................................28Regolith geology ..................................................................................................................................................28

Residual or relict units ..................................................................................................................................28

iv

Depositional units .........................................................................................................................................29Alluvial deposits ....................................................................................................................................29Sheetwash deposits ................................................................................................................................29Colluvial deposits ...................................................................................................................................29Lacustrine deposits .................................................................................................................................30Sandplain deposits .................................................................................................................................30

Economic geology ................................................................................................................................................30Gold ...............................................................................................................................................................30Nickel and cobalt ..........................................................................................................................................31Base metals ...................................................................................................................................................32Other commodities ........................................................................................................................................32

Iron and manganese ...............................................................................................................................32Uranium .................................................................................................................................................32Tin ..........................................................................................................................................................32Diamonds ...............................................................................................................................................33Magnesium .............................................................................................................................................33Phosphate, rare earth elements, niobium, and tantalum .........................................................................33Tungsten .................................................................................................................................................33Molybdenum ..........................................................................................................................................33Bismuth ..................................................................................................................................................33Lithium–tantalum–beryl ........................................................................................................................33Semiprecious gemstones ........................................................................................................................33

References ............................................................................................................................................................34

Appendices

1. Standardized regolith and rock codes of the East Yilgarn 1:100 000 Geological InformationSeries database ...........................................................................................................................................42

2. WAMIN database .......................................................................................................................................54 3. Gazetteer of localities .................................................................................................................................58

Figures

1. Tectonic subdivisions of the Archaean Yilgarn Craton ................................................................................2 2. Extent of the East Yilgarn 1:100 000 Geological Information Series database area ....................................3 3. Tectonic subdivision of the Eastern Goldfi elds Granite–Greenstone Terrane ..............................................8

Tables

1. 1:100 000-scale geological maps and Explanatory Notes collated in the East Yilgarn 1:100 000 Geological Information Series database .....................................................................................4

2. Granite groups in the Eastern Goldfi elds Granite–Greenstone Terrane ....................................................12 3. Summary of proposed regional deformation events in the Eastern Goldfi elds

Granite–Greenstone Terrane .......................................................................................................................14

East Yilgarn 1:100 000Geological Information Series

— an explanatory note

by

P. B. Groenewald and A. Riganti

AbstractFifty-seven 1:100 000-scale geological maps of the Eastern Goldfi elds Granite–Greenstone Terrane,Western Australia, have been collated as geospatially referenced digital information in the East Yilgarn 1:100 000 Geological Information Series database. Original map boundary discrepancies have beenresolved and rock type defi nitions standardized for outcrop geology, and the entire regolith geology reinterpreted, to provide seamless coverage. Rock type defi nitions and coding have been revised into formats suitable for the inclusion of this database into a State-wide coverage.

The 154 000 km2 area includes 15 700 km2 of basement outcrop that comprises 7500 km2 of Archaean supracrustal rocks, and a similar area of granitic rocks, with the remainder consisting of Proterozoic basin deposits. The major part of the area is overlain by Cainozoic rocks and regolith. Spatial data for thissurface geology encompass 48 000 polygons for rock outcrop and 45 000 for regolith, 13 500 structural lines (4005 for faults), and 21 000 structural observation points.

These data reveal the great diversity of rock types, but defi nitive intervals of Archaean lithostratigraphy within the greenstone belts are limited, of variable extent and continuity, and of restricted correlation. Although detailed interpretation of the Archaean geology is inhibited by the lack of continuous outcrop,a complex deformation history is being researched and recent literature reveals advances in interpretation. Several extensive, elongate lithostratigraphic terranes can be distinguished, supported by recognized characteristics typical of different tectonic settings. Ongoing geochronological, geophysical, andgeochemical studies are clarifying this interpretation.

Several other data themes are also provided, including:• an interpretation at 1:500 000 of Precambrian geology beneath younger cover;• aeromagnetic data from Geoscience Australia, comprising a recent 400 m line spaced survey north of

29°30'S and older, more widely spaced, surveys to the south;• an aeromagnetic interpretation of concealed features;• mineral occurrence localities and attributes;• mineral resource locations and statistics;• tenement distribution and status information;• pseudocolour images derived from Landsat TM data.

Future advances in the East Yilgarn 1:100 000 Geological Information Series will include expanded coverage in terms of areal extent, as well as additional themes such as gravimetric and radiometric data.

KEYWORDS: Yilgarn Craton, Eastern Goldfi elds, GIS database, Archaean geology, greenstones,remote sensing, mineral resources, gold, nickel.

IntroductionThe 2004 release of the East Yilgarn 1:100 000 Geological Information Series consists of a seamless digital dataset for 57 standard 1:100 000-scale map sheets (Figs 1 and 2; Table 1) covering most of the Eastern Goldfi elds Granite–Greenstone Terrane (EGGGT) of the Archaean

Yilgarn Craton. The dataset was collated in three stages of compilation and standardization of the published geological maps (formerly called the East Yilgarn Geoscience Database; Groenewald et al., 2000, 2001; Painter et al., 2003), and includes a reinterpretation of the entire regolith geology (Riganti et al., 2003). A lithological classifi cation and coding scheme has been applied to

1

Groenewald and Riganti

Figure 1. Tectonic subdivisions of the Archaean Yilgarn Craton (after Tyler and Hocking, 2002)

200 km

Inferred fault

Granite

Greenstone

Fault

PERTH

SOUTHERN OCEAN

INDIANOCEAN

24°

28°

32°

116° 120° 124°

Kalgoorlie–Boulder

IdaFault

PBG21 07.12.04

Area of East Yilgarn1:100 000 Geological Information

Series 2004 data release

NarryerTerrane

MurchisonGranite–Greenstone

Terrane

SouthWest

Terrane

SouthernCross

Granite–Greenstone

Terrane

EasternGoldfieldsGranite–

GreenstoneTerrane

ensure compatibility with future Geological Survey of Western Australia (GSWA) database developments. This work represents a substantial revision of all maps produced by GSWA and Geoscience Australia (GA; formerly the Australian Geological Survey Organization — AGSO, and prior to that the Bureau of Mineral Resources — BMR) under the National Geoscience Mapping Accord (NGMA) for the Eastern Goldfi elds Granite–Greenstone Terrane.

A summary of the explanatory notes provided with each stage in the evolution of this database is presented here, together with an outline of the recent advances in the geological understanding of the region. The descriptions

2

provided with previous database releases (Groenewald et al., 2000, 2001; Painter et al., 2003; Riganti et al., 2003) are not replaced by the present manuscript. Users in need of more detailed information are still advised to refer to the original explanatory notes written for individual 1:100 000 maps, as listed in Table 1. The revised rock type classifi cation scheme (Tyler et al., in prep.) has been applied and the consequent map codes and defi nitions are provided in Appendix 1.

This Report also provides a description of the digital themes into which the data have been divided. Details of metadata, data attributes, and look-up tables are

GSWA Report 95 East Yilgarn 1:100 000 Geological Information Series — an explanatory note

3

CUNYU MILLROSE BALLIMORE

WILUNA LAKE VIOLET SANDALWOOD

YEELIRRIE MOUNT KEITH WANGGANNOO TATE URAREY DE LA POER

DEPOTSPRINGS

SIR SAMUEL DARLOT BANJAWARN DUKETONCOSMO

NEWBERY

MUNJEROO WILDARA WEEBO NAMBI MOUNTVARDEN

McMILLAN

MOUNTALEXANDER

WILBAH LEONORA MINERIE LAVERTON BURTVILLE

MOUNTMASON BALLARD MELITA YERILLA LAKE CAREY MOUNT CELIA

MULLINE RIVERINA MENZIES BOYCE EDJUDINA YABBOO

DAVYHURST BARDOC GINDALBIE MULGABBIE PINJIN

DUNNSVILLE KALGOORLIE KANOWNA KURNALPI ROE

YILMIA LAKE LEFROY MOUNTBELCHES

COWAN

NORSEMANBOYCE

Banjawan Duketon

Kanowna

Yakabindie

Mt Keith

Ora Banda

Broad Arrow

Laverton

Leinster

Menzies

Norseman

Widgiemooltha

Cosmo Newbery

Millrose

Davyhurst

Cunyu

Wiluna

Mt Murrin MurrinLeonora

Kambalda

Kalgoorlie–Boulder

Coolgardie

Regolith

Proterozoic rocks

Greenstone

Granite

Town

Locality

Homestead

120° 121°

122° 123°

26°

27°

28°

29°

30°

31°

32°

PBG22 01.10.04

Wildara

Mt Clifford

Kurrajong

Bulong

Marshall Pool

1:100 000 map sheet

50 km

Figure 2. Extent of the East Yilgarn 1:100 000 Geological Information Series database area, covering 57 standard 1:100 000-scale map sheets and about 154 000 km2 of the Eastern Goldfi elds Granite–Greenstone Terrane


Table 1. 1:100 000-scale geological maps and explanatory notes collated in the East Yilgarn 1:100 000 Geological Information Series database

Name Map reference Explanatory Notes

BALLARD Rattenbury and Stewart (2000) –BALLIMORE Blake and Whitaker (1996a) Whitaker et al. (2000)BANJAWARN Farrell and Griffin (1997) –BARDOC Witt and Swager (1989a) Witt (1994a)BOYCE Chen and Witt (1998) –BURTVILLE Duggan (1995a) –COSMO NEWBERY Griffin and Farrell (1998) –COWAN Griffin (1988) Griffin (1990b)CUNYU Adamides et al. (1998) Adamides et al. (1999)DARLOT Wyche and Westaway (1996) Westaway and Wyche (1998)DAVYHURST Wyche et al. (1992) Wyche and Witt (1994)DE LA POER Stewart (1996a) Stewart (1999)DEPOT SPRINGS Wyche and Griffin (1998) –DUKETON Farrell and Langford (1996) Langford and Farrell (1998)DUNNSVILLE Swager (1989a) Swager (1994a)EDJUDINA Swager and Rattenbury (1994) Swager (1995b)GINDALBIE Ahmat (1995b) –KALGOORLIE Hunter (1988a) Hunter (1993)KANOWNA Ahmat (1995c) Ahmat (1995a)KURNALPI Swager (1993) Swager (1994b)LAKE CAREY Rattenbury and Swager (1994) –LAKE LEFROY Griffin and Hickman (1988) Griffin (1990b)LAKE VIOLET Stewart and Bastrakova (1997) –LAVERTON Stewart (1996b) –LEONORA Stewart and Liu (1997) Williams (1998)MCMILLAN Champion and Stewart (1996a) – Duggan (1995b) –MELITA Witt (1990) Witt (1994b)MENZIES Swager and Witt (1990) Swager (1994c)MILLROSE Farrell and Wyche (1997) Farrell and Wyche (1999)MINERIE Williams et al. (1995) –MOUNT ALEXANDER Duggan (1995c) –MOUNT BELCHES Painter and Groenewald (2000) Painter and Groenewald (2001)MOUNT CELIA Duggan (1995d) –MOUNT KEITH Jagodzinski et al. (1997) Jagodzinski et al. (1999)MOUNT MASON Wyche (2003) –MOUNT VARDEN Rattenbury et al. (1996) –MULGABBIE Morris (1994b) Morris (1994a)MULLINE Wyche (1995) Wyche (1999)MUNJEROO Duggan et al. (1996b) –NAMBI Jagodzinski et al. (1996) –NORSEMAN McGoldrick (1993) –PINJIN Swager (1994e) Swager (1994d)RIVERINA Wyche and Swager (1995) Wyche (1999)ROE Smithies (1994b) Smithies (1994a)SANDALWOOD Blake and Whitaker (1996b) Whitaker et al. (2000)SIR SAMUEL Liu et al. (1996) Liu et al. (1998)TATE Champion (1996) –URAREY Champion and Stewart (1996b) Stewart (1999)WANGGANNOO Lyons et al. (1996) –WEEBO Oversby et al. (1996a) –WILBAH Duggan et al. (1996a) –WILDARA Oversby et al. (1996b) –WILUNA Langford and Liu (1997) Langford et al. (2000)YABBOO Swager (1994f) Swager (1995b)YEELIRRIE Champion and Stewart (1998) –YERILLA Oversby and Vanderhor (1995) –YILMIA Hunter (1988b) Hunter (1993)

4


5

provided in the ‘Readme’ and data dictionary fi les on the accompanying DVD.

Location, access, and physiographyThe area covered by the database lies between 120° and 123°E, from a northwestern limit at 26°S to a southern boundary at 32°30'S (Figs 1 and 2).

Bitumen highways link the city of Kalgoorlie–Boulder, which is in the central-southern part of the project area, to Wiluna in the north, Laverton in the northeast, and Norseman in the south. Good-quality gravel roads provide access to mining centres and pastoral holdings throughout the region. In addition, an extensive network of variably maintained pastoral tracks and fence lines allows access to most localities.

The landscape is relatively subdued, with a total elevation range from 270 to 650 m above the Australian Height Datum (AHD). The extent to which physiography is related to the underlying geology is illustrated by northwest-trending broad ranges of hills formed by northwest-striking metamorphosed mafi c volcanic and chert or banded iron-formation units in the greenstone belts. These strike ridges are interspersed with gently undulating areas underlain by metamorphosed felsic volcanic and sedimentary rock types, with low plateaus of duricrust and deeply weathered bedrock. The large expanses between the greenstone belts are underlain by granite, granitic gneiss, and their weathered counterparts, and are typically characterized by undulating plains that are locally disrupted by breakaways or scarps.In these areas, sandy soils of granitic compositioncommonly overlie siliceous duricrust and kaolinitized granite and, less commonly, fresh rock. Extensive areas of limited relief are covered by siliceous or ferruginous duricrust (‘laterite’ in many early descriptions).

The other notable landforms are the saline playa lakes and claypans that cover substantial areas. Commonly, these are the relics of a southeasterly to easterly trending early Cainozoic palaeodrainage system. The lakes are commonly fl anked by dunes of quartz sand or gypsum (or both), typically stabilized by scrubby vegetation, interspersed with minor alluvial salt pans and evaporite deposits.

The databaseThe original 1:100 000-scale geological maps werecollated (Fig. 2) with attention to fi delity of data transfer and elimination of discrepancies between adjacent mapsheets, as described in Groenewald et al. (2000, 2001) and Painter et al. (2003). Riganti et al. (2003) provided a complete revision of the regolith interpretation and thefi nal adjustments to the seamless outcrop geology.

The database has been assembled using the Environ-mental Systems Research Institute (ESRI) softwareArcInfo 8.0.1 to yield seamless layers within a digital

map library. The library was then converted into formatssuitable for application of popular Geographic Information System (GIS) software packages such as ArcView, ArcExplorer, and MapInfo. Details of the directorystructure, data dictionary, and other metadata are provided in text fi les on the accompanying DVD.

LayersThe database contains a variety of data types in necessarily diverse formats, all linked by spatial attributes. This requires subdivision of the data into different packages of information or ‘layers’. Much of the power of GIS stems from this subdivision in that it enhances selective access to data for the application of analytical methodology. The layers used in this database are detailed below.

Geology

The geological data are subdivided according to the following attributes:• The distribution and nature of outcrop and regolith

units are recorded as polygons. Outcropping planar units, represented by lines on the original maps because they were too narrow to be drawn as polygons, have been redefi ned as 10 m-wide polygons to allow inclusion in a single dataset more suitable for GIS analysis. Attributes of each polygon include a rock type code for labelling, with standardized defi nitions provided in Appendix 1 and database look-up tables.

• Outcropping faults or shears, lineaments, and joints are provided as a line data layer.

• Point records represent sites at which fi eld observations were made of outcrop geology, including orientation measurements of primary and secondary planar and linear structural features.

It should be noted that outcrop geology data have been derived from published map sheets, 26 of which were mapped by GA and 31 by GSWA. Regional-scale remapping of the Eastern Goldfi elds Granite–Greenstone Terrane has not been undertaken, although numerous local areas were studied to ensure continuity across former map sheet boundaries.

Subsurface observations

Subsurface records of rock types (from drillholes and costeans) are provided in a point dataset derived from the published maps, with limited additions in some areas. These points are useful for interpretation of the regional bedrock geology because there are no clear geophysical distinctions between felsic volcanic rocks and sedimentary rocks, and between these and some of the granites.

Exploration drilling has provided an enormous resource of subsurface observations, and considerably more localities are available from the open-fi le statutory company reports in the Department of Industry and Resources’ (DoIR’s) Western Australian mineral exploration (WAMEX) database.


6

Regional interpreted bedrock geology

The interpreted bedrock geology layer in the database is a map of the interpreted distribution of Precambrian rock types beneath younger cover. This is taken from the continuous Western Australian 1:500 000-scale coverage completed in 2001 by GSWA. Polygon and line data are in separate layers. Note that the map of interpreted solid geology, although based on the 1:100 000-scale maps, was compiled for presentation at a scale of 1:500 000 and thus may not conform precisely with the outcrop geology maps. Also note that the coding and legend for this theme are different from the geology layer.

Aeromagnetic data

The aeromagnetic survey layer is the GA dataset, comprising earlier (1965–1967) BMR and more recent AGSO (1995) data. For the area north of 29°30'S, a line spacing of 400 m allows the use of 100 m pixels, suitable for 1:100 000-scale interpretation of the subsurface geology. However, the southern part was fl own at 1600 m line spacing, which allows imaging at no better than 400 m pixels, only suitable for interpretation at 1:250 000 or smaller regional scale.

Aeromagnetic interpretation

Linear and polygon magnetic features identifi ed in the detailed airborne magnetic coverage are provided as aeromagnetic interpretation layers, entirely based on data at 200 to 400 m fl ight-line spacings. This geological interpretation shows the distribution of principal rock types and features such as linear anomalies and discontinuities. It represents an extract from a coverage of the entire Yilgarn Craton by Whitaker and Bastrakova (2002).

Landsat 7 TM

The Landsat 7 TM layers contain images prepared using data collected in 2002 in which most mining excavations and recent exploration grids are visible. Data from several Landsat scenes have been merged using robust regression techniques to provide a seamless image. Spatial accuracy better than 50 m, with a pixel size of 25 m, has been preserved. Raw data may be purchased from the Satellite Remote Sensing Services branch of the WesternAustralian Department of Land Information (DLI).

A monochromatic (grey-scale) layer shows principal component values derived from Landsat TM bands 1, 4, and 7 using standard eigenvector formulae. In addition, a decorrelation stretch image has been created for bands 7 (red), 5 (green), and 4 (blue) that provides good discrimination between iron- and silica-rich areas, and between vegetation- and outcrop-dominated areas.

WAMIN

The WAMIN theme (derived from the Western Australian mineral occurrence database of GSWA) contains

geoscience attribute information on mineral occurrences in the East Yilgarn database area. The data include the localities and commodity groups of abandoned and currently operating mines and batteries, all mineral deposits for which there are established resource estimates, and prospects with reported mineralization but no recorded production. Appendix 2 provides details of the classifi cation scheme used in this theme. The high level of exploration activity in the region in the 1980s and 1990s led to an increase in the resource inventory, particularly near abandoned mines. Therefore, the more recent fi nds in the DoIR mines and mineral deposits information database (MINEDEX; see below), may provide location coordinates for named historical localities slightly different from those in the WAMIN dataset. Similarly, present large-scale opencut mining operations have commonly amalgamated several historical mine sites.

MINEDEX

The extract from the mines and mineral deposits information (MINEDEX) database included in the East Yilgarn database provides the following information, either directly as point-attribute information or in look-up tables:• commodity groups, projects, and sites;• corporate ownership and percentage holding;• site type and stage of development;• site coordinates;• current (at date of DVD compilation) mineral resource

estimates.

TENGRAPH

The tenement information within the database is extracted from DoIR’s electronic tenement graphics system (TENGRAPH). The information demarcates the extent and location of tenements, with the following additional data in the attribute table:• tenement identifi cation (Tenid; e.g. M 2600261 refers

to mining licence M 26/261);• survey status (Survstatus), indicating whether or not

the tenement has been surveyed;• status of the tenement (Tenstatus), referring to whether

the tenement has been granted (L, i.e. ‘live’) or is under application (P, i.e. ‘pending’);

• dates and times of submission of application, and granting and expiry of tenement holding.

Because of the continuous and ongoing changes in the tenement situation, current tenement plans at the DoIR offi ces in Perth and several mining towns should be viewed before any land-use decisions or tenement applications are made. Monthly tenement updates are available on the DoIR website (www.doir.wa.gov.au).

Geological setting of the Eastern Goldfi elds region

The Archaean Yilgarn Craton contains fi ve geological elements (Fig. 1), of which the Eastern Goldfields


Granite–Greenstone Terrane (Tyler and Hocking, 2001, 2002) is the most extensive, making up the eastern-third of the craton and differing from the adjacent Southern Cross Granite–Greenstone Terrane (SCGGT) in terms of age and general lithostratigraphy (Gee et al., 1981; Chen et al., 2003). There are more Archaean supracrustal rocks (greenstones) in the EGGGT than in the other terranes, but they still do not amount to more than 30% of the area — the remainder consists entirely of granite and quartzo-feldspathic gneiss.

Age constraints on the Eastern Goldfi elds supercrustal rocks obtained by sensitive high-resolution ion microprobe (SHRIMP) U–Pb analysis reveal that the general ages of eruption and deposition are between 2725 and 2660 Ma (Kent and Hagemann, 1996; Nelson, 1995, 1996, 1997a,b, 1998, 2000; Krapez et al., 2000), with a few local exceptions. Although no basement has been confi rmed in the EGGGT, pre-existing continental crust is suggested by the xenocrystic zircons older than 3000 Ma in metamorphosed felsic volcanic rocks (Compston et al., 1986; Nelson, 1997a). This is supported by the trace element geochemistry of some mafi c rocks that indicate contamination of a primitive ultramafi c magma by older sialic crust (Arndt and Jenner, 1986; Barley, 1986; Lesher and Arndt, 1995), and of granites that indicate generation through repeated crustal reworking (e.g. Wyborn, 1993). Felsic volcanic complexes, ranging in age from c. 2760 to 2670 Ma (Pidgeon and Wilde, 1990; Pidgeon and Hallberg, 2000), are widespread in the Yilgarn Craton. The different petrogenetic and geochronological characteristics of the main felsic volcanic centres within the EGGGT support recognition of originally separate tectono-stratigraphic terranes (Brown et al., 2001).

The greenstone sequences of the SCGGT have yielded ages of c. 3000–2900 Ma by SHRIMP U–Pb analysis of zircons from samples of the extensive lower mafi c–ultramafi c rock association, with late localized volcanic activity at c. 2725 Ma (Pidgeon and Wilde, 1990; Nelson, 1999).

Extent of the Eastern Goldfi elds Granite–Greenstone TerraneThe western limit of the EGGGT has been equated to the Ida Fault, which is best recognized in the Davyhurst area, west of Ora Banda (Fig. 3). In the interpretation of seismic traverse BMR91EGF01, completed in 1991, this fault is a planar 30° east-dipping, crustal-scale structure coincident with crustal thickening of more than a kilometre (Drummond et al., 1993; Goleby et al., 1993; Swager et al., 1997). Although considered an accretionary boundary between the EGGGT and the older SCGGT (Myers, 1997), in the seismic section this fault is extensional with downthrow to the east. The Ida Fault is not clearly established north and south of the Davyhurst area. To the north, the inferred boundary continues as the Ida Shear within the Mount Ida greenstone belt (e.g. Swager et al., 1995; Fig. 3) or in granites to the west (e.g. Griffi n, 1990a,b). Stratigraphic relationships of the southern Mount Ida greenstone belt indicate that the ultramafi c-bearing eastern portion of the belt is part of the EGGGT, and that the basalts and cherts of the western

7

portion are part of the SCGGT (e.g. Wyche, 1999). Recent aeromagnetic interpretations have inferred that the Ida Shear is discontinuous along strike (Whitaker, 2002), but its precise location to the north is unclear. The most likely extension is inferred to be along the western limb of the Lawlers fold in the southwestern Agnew–Wiluna greenstone belt (Fig. 3), and to the north either along the western limit of the greenstone belt or farther west, cutting through the belt near Wiluna. To the south of the 1991 seismic traverse, the Ida Fault has been traced into the area west of Coolgardie. It has not been tracked any farther south because this area has extensive granitic intrusions and no major faulting can be interpreted from existing geophysical data.

Tectono-stratigraphy of the Eastern Goldfi elds Granite–Greenstone TerraneThe greenstones of the EGGGT were subdivided into tectono-stratigraphic terranes (Swager et al., 1990, 1995; Myers, 1990, 1995, 1997; Myers and Swager, 1997), after Barley et al. (1989) had interpreted the region in a plate tectonic setting. The terranes include Kalgoorlie, Gindalbie, Norseman, Kurnalpi, Laverton, and Edjudina (Fig. 3). Terrane nomenclature was based on lithostratigraphic distinctions between the terranes, mainly variations in volcanic and sedimentary components characteristic of different arc environments, with the terranes brought together in an accretionary tectonic setting. The subdivision was further documented by Brown et al. (2001), who detailed the consistent differences in the nature of felsic volcanic components of the different terranes. Although there are geochronological data that support the terrane hypothesis, Nelson (1997a) and GSWA (2004) provided age data that indicate synchronous komatiitic volcanism in several of the central and western terranes of the EGGGT, and further work is required to resolve the extensive continental infrastructure implied by the widespread occurrence of xenocrystic zircon. Conglomeratic sequences that were deposited during extensional stages of the Wangkathaa Orogeny (Blewett et al., 2004) are widely distributed in the EGGGT, and are preserved in fault-bound troughs that post-date early deformation and assembly of the terranes.

The original terrane boundaries have been obscured by considerable post-accretionary deformation, but may be partly equivalent to the regional-scale, north-northwesterly trending structures that were active in later deformational events. In the present overview, the tectono-stratigraphic terrane subdivision is applied, albeit with the caveat that boundaries are poorly constrained and the original dispersion of the terranes is unknown. As noted by Swager (1997), the ‘terranes’ may represent remnants of adjacent contemporaneous environments, rather than far-travelled or exotic crustal fragments.

In the discussion that follows, reference is made to domains, greenstone belts, and structural elements that have been described in some detail in the notes that accompanied the previous East Yilgarn Geoscience Database compilations (Groenewald et al., 2000, 2001;


8

01AGS-NY1

EGF1

PROTEROZOIC ROCKS

Earaheedy Group

Yerrida Group

ARCHAEAN LITHOLOGIES

Chert and banded iron-formation

Late siliciclastic conglomerates

Sedimentary rocks

Felsic volcanic andvolcaniclastic rocks

Mafic igneous rocks

Komatiitic and ultramafic rocks

Granites and quartzofeld-spathic gneiss

PBG23 19.10.04

120° 121°

122° 123°27°

26°

28°

29°

30°

31°

32°

Fault

Town

Terrane

Areas referred to in text

Laverton

Leonora

Kalgoorlie

So

uth

ern

Cro

ssG

ran

ite–

Gre

enst

on

eTe

rran

e

Eastern GoldfieldsGranite–Greenstone

TerraneKurnalpi

Laverton

Kalgoorlie

Gindalbie

Edjudina

Norseman

Illaara

Kurnalpi

PerseveranceFault

Ninnis

Fault

Du

keton

Fault

Ida Fau

lt

Mt M

onger Fault

Em

uFault

Claypan Fault

Bu CoOB

Bo

Pa

Kb

Wiluna

MountKeith Dingo

RangeYandal

JonesCreek

Duketon

CosmoNewbery

Agnew

MountIda

Murrin

WelcomeWell

Melita

Yilgangi

Ora Banda

PennyDam

Bulong

MountBelches

Merougil Duketon

BullabullingBuCoolgardieCoOra BandaOBKambaldaKbBooraraBoParkerPa

Domains:

Seismic line

50 km

Figure 3. Tectonic subdivision of the Eastern Goldfi elds Granite–Greenstone Terrane (modifi ed after Myers, 1997; Swager et al., 1995; Swager, 1995a; Brown et al., 2001; Chen et al., 2001)

GSWA Report 95 East Yilga

9

Painter et al., 2003). A detailed characterization of these geological elements is not within the scope of this publication, and the reader is referred to these previous publications and the references cited therein. The attribution of all rock occurrences to specifi c terranes will be possible once the terrane boundaries have been identifi ed throughout the EGGGT.

Kalgoorlie terraneThe Kalgoorlie terrane is the most extensive recognized terrane, extending the length of the Eastern Goldfi elds (Fig. 3). This terrane may be greater in extent than defi ned by Myers (1997) because geochemical studies by Messenger (2000) of the Yandal greenstone belt, currently attributed to the Kurnalpi terrane, strongly support correlation between the rocks of the Kalgoorlie terrane and Yandal greenstone belt.

Clearly defined lithostratigraphic sequences are restricted to areas such as Kambalda and Ora Banda in the Kalgoorlie terrane, and stratigraphic unit names are used only for the uppermost units that are of limited extent. Although several studies (references cited by Groenewald et al., 2000, 2001) have provided details that allow subdivision of this terrane into lithostratigraphic domains (Fig. 3), considerable lithological and chronological similarities exist between the southern (Kalgoorlie) and northern (Agnew–Wiluna, Yandal) sections in any one area (Libby et al., 1998; Messenger, 2000). The most complete sequence consists of lower basalts, overlain by a komatiite unit that is in turn overlain by an upper basalt unit, followed by felsic volcanic and sedimentary rocks.

The lithostratigraphy can be summarized as follows:• The lower basalt unit consists of greenschist- to

amphibolite-facies rocks, with weak to intense penetrative foliation partly obscuring primary features such as pillow lavas, fl ow-top breccias, and amygdales. An upward change from komatiitic to tholeiitic rocks was documented by Redman and Keays (1985). Felsic volcaniclastic rocks interfi nger with the basalts at several localities.

• A prominent and regionally extensive sequence of komatiites (up to several kilometres thick) overlies the lower basalt unit. Olivine spinifex-textured komatiite is the dominant rock type in lower parts, whereas the upper part consists of variolitic komatiitic basalt. The komatiitic fl ows range from 2 m to more than 100 m thick, and are locally separated by thin (<5 m), fi ne-grained metasedimentary beds. In the Ora Banda, Kurrajong, Mount Pleasant, and Mount Keith areas, the komatiites include distinctive thick dunitic and peridotitic units, interpreted by Hill et al. (1989, 1995) as cumulates in infl ated lava fl ows.

• An upper basalt unit that overlies the komatiites contains both tholeiitic and komatiitic basalts. Some thick differentiated fl ows or subvolcanic sills have been identifi ed. Compositional diversity in these rocks is the result of assimilation, by komatiitic lavas, of up to 25% granitic crustal material (Arndt and Jenner, 1986).

• The felsic volcanic – sedimentary package that unconformably overlies the mafi c–ultramafi c volcanic succession has been named the Black Flag Group in

rn 1:100 000 Geological Information Series — an explanatory note

the south. Similar rocks in the Yandal greenstone belt to the northeast are probable correlatives (Messenger, 2000). The thickness of this unit varies from 450 to 3000 m. These rocks are mostly volcaniclastic sandstones, agglomerates, and debris flows, but lava fl ows are recognized locally. They are closely interbedded with siltstone and sandstone that have quartzofeldspathic compositions consistent with derivation from the associated volcanic rocks. Oligomictic conglomerates at numerous levels in the sequence are dominated by feldspar–quartz porphyry clasts. The association of fi ne-grained sedimentary units with conglomeratic horizons suggests a submarine environment, subjected to periodic infl uxes of large-scale debris fl ows, refl ecting proximal tectonic exhumation during deposition (Krapez et al., 2000). The overall characteristics suggest accumulation in an environment of ongoing volcanism and intermittent extension, with deep-water conditions and a considerable infl ux of sedimentary debris.Krapez et al. (2000) defi ned two unconformity-bound sequences within the Black Flag Group beds — the Spargoville and Kalgoorlie sequences.

• The uppermost unit contains conglomeratic to arenaceous sedimentary rocks limited to unconformity or fault-bound (or both) synclinal basins elongated parallel to the regional tectonic grain. These are the submarine-fan (Kurrawang sequence) and braided-fl uvial (Merougil and Jones Creek sequences) deposits that accumulated during extensional stages of the Wangkathaa Orogeny (Blewett et al., 2004), but before fi nal deformation and metamorphism.

Gindalbie terrane

The Gindalbie terrane is east of the Kalgoorlie terrane between the Mount Monger and Emu Faults (Fig. 3). The Gindalbie terrane is distinguished by the presence of both bimodal (basalt–rhyolite) and calc-alkaline intermediate to silicic volcanic successions, in addition to the komatiitic rocks typical of the Kalgoorlie terrane. The structurally lowermost calc-alkaline succession, ranging from basaltic andesite to rhyolite in composition, has an age of 2672 ± 12 Ma (Nelson, 1995). An ultramafi c–mafi c association, dated at 2705 ± 4 Ma (Nelson, 1995), is older than the underlying calc-alkaline rocks, supporting a map interpretation of thrust faulting (Ahmat, 1995a). The third, structurally highest, succession is a bimodal suite with dacite dated at 2681 ± 5 Ma (Nelson, 1995).

The northern part of the Gindalbie terrane includes three signifi cant bimodal and felsic subalkaline volcanic complexes known as the Melita, Teutonic Bore, and Jeedamya Complexes. The Melita Complex is a bimodal package comprising rhyolitic to dacitic lavas and volcaniclastic rocks interlayered with pillow basalts and mafi c hyaloclastites (Witt, 1994a; Brown et al., 2001). The Brown et al. (2001) defi nition of the Melita Complex differs from those of previous workers in that it includes the interbanded volcanic, volcaniclastic, and intrusive mafi c units that Hallberg (1985) and Witt (1994a) excluded from the Melita Complex. The felsic rocks in particular are enriched in incompatible elements, more


1

so than other felsic rocks of the EGGGT. Morris and Witt (1997) considered the sequence to have resulted from anhydrous melting of tonalite, whereas Brown et al. (2001) considered it to represent partial melting of intermediate arc-type crust.

The Teutonic Bore Complex is strongly deformed and attenuated, and comprises andesite and pillow basalt interbedded with thick beds of silicic volcaniclastic rocks and rhyolite lava (Brown et al., 2001). Compositionally similar syenogranite and alkali-feldspar granite associated with this complex are probably genetically related to the volcanic rocks (Brown et al., 2001).

The Jeedamya Complex is a calc-alkaline intermediate–silicic complex consisting predominantly of rhyolitic to rhyodacitic pyroclastic and volcaniclastic rocks (Witt, 1994a). A broad area of laterite separates the Jeedamya and Melita Complexes, so the nature of the contact between them is unclear.

Although lithologically different from the adjacent Kalgoorlie terrane, the chronological distinction between the terranes is statistically insignifi cant, and both lithotectonic packages have very similar structural histories.

Kurnalpi terrane

The Kurnalpi terrane, immediately east of the Gindalbie terrane, is bound by the Emu, Clay Pan, and Ninnis Faults (Fig. 3).

The southwesternmost greenstones in this terrane dip and face west, and are mainly composed of basalt, with several units of komatiite. Lateral changes from basalt- to felsic epiclastic-dominated packages are interpreted as original depositional features (Swager, 1995a). Nelson (1995) dated a felsic volcanic unit between two komatiite layers near Murrin Murrin at 2706 ± 3 Ma, an age equivalent to similar associations in the Kalgoorlie terrane.

East and north of the greenstones described above, several east-facing mafi c–felsic volcanic and volcaniclastic packages show substantial lateral variations in mafi c versus felsic rock abundances. A major shear zone in this area separates upper rocks dated at 2684 ± 3 Ma (Nelson, 1995) from a lower felsic fragmental unit dated at 2708 ± 7 Ma (Nelson, 1997b). Farther north, in the Yilgangi area, tholeiitic basalt and minor komatiite are interleaved with, and overlain by, felsic volcanic and epiclastic rocks. Ultramafi c rocks are dominantly olivine-cumulate peridotites, with minor gabbro, komatiitic basalt, and some olivine spinifex-textured fl ows.

The Murrin sector of the Kurnalpi terrane, east and northeast of Leonora, is characterized by three volcanic and volcaniclastic associations (Groenewald and Doyle, 2004). The lowermost association is the Welcome Well Complex, which is a sequence of andesitic volcaniclastic rocks and associated epiclastic rock. The overlying association contains very well exposed pillow basalts with substantial hyaloclastite interlayers, indicative of

0

at least localized emergence. These rocks are succeeded by a komatiitic succession that includes layered mafi c to ultramafi c complexes, in which olivine adcumulates, orthocumulates, and olivine gabbro are closelyassociated with pyroxene spinifex-textured komatiitic basalts. The mafi c to ultramafi c Murrin Murrin Complex, which forms the thickest part of this association, has been recognized as an extensive ponded komatiitic lava lake unit in which differentiation led to the formation of substantial olivine orthocumulates (Hill et al., 2001). Extensive laterite development over these ultramafi c rocks has formed the giant supergene nickel–cobalt deposits at Murrin Murrin.

Laverton terrane

The Laverton terrane, northeast of the Kurnalpi terrane, is a triangular area between the Ninnis and Duketon Faults (Fig. 3). In the south it includes the Laverton greenstone belt, whereas the northern parts include the Duketon and Dingo Range greenstone belts. The Margaret Anticline in the Laverton greenstone belt consists almost entirely of mafi c rocks, dominated by basalt, komatiitic basalt, dolerite, and gabbro, with less abundant komatiite units. The lowermost part of the stratigraphy is preserved at Mount Windarra and South Windarra, where basal BIF is overlain by ultramafi c schist and basalt.

The Duketon greenstone belt contains mafi c and ultramafic rocks, felsic volcanic and volcaniclastic rocks, chert, shale, sandstone, and conglomerate. The poor exposure, deep weathering, lack of younging indicators, and structural complexity have prevented recognition of any well-constrained lithostratigraphy. About half of the greenstone belt consists of mafi c rocks (commonly tholeiitic basalt, komatiitic basalt, and gabbro), but metamorphism and weathering prevent detailed interpretation. A thick succession of felsic volcanic, volcaniclastic, and sedimentary rocks is present, but the only possible markers are BIF units. In the central, possibly uppermost, part of the belt, the exposed greenstones are exclusively felsic volcanic and volcaniclastic rocks. Conglomerates with felsic volcanic and granitic clasts near the western margin may represent a similar setting to the Jones Creek Conglomerate in the Agnew–Wiluna greenstone belt.

Hallberg (1985) interpreted the lithostratigraphy of the Laverton greenstone belt as an earlier association than that immediately to the west in the Kurnalpi terrane. His interpretation was based largely on the presence of komatiites, abundant BIF, and quartz-rich sedimentary rocks in the Laverton greenstone belt, and their apparent absence farther west.

The subsequent classifi cation of the Murrin Murrin igneous complex as komatiitic and the presence of substantial chert units at a stratigraphic position equivalent to the BIF in the east (i.e. an iron-poor lateral-facies ?BIF equivalent) suggest that Hallberg’s (1985) interpretation may have been incorrect. Geochronological investigation is required to elucidate the lithostratigraphic validity of this boundary.


11

Edjudina terrane

The Edjudina terrane (Fig. 3) comprises tholeiitic basalt, minor komatiite, calc-alkaline volcanic complexes, and extensive volcaniclastic, epiclastic, and conglomeratic successions that have regional marker horizons of BIF, chert, and slate. The BIF units, which may be traced for several hundred kilometres along strike, are an important distinguishing feature not present in other terranes of the EGGGT. Several andesitic volcanic complexes and laterally extensive belts of epiclastic debris are associated with tholeiitic and komatiitic basalts, suggesting synchroneity of these compositionally diverse magmatic events. The considerable extent of late conglomeratic rocks has become evident in the course of recent mining developments in the area south of Laverton. Major mines, such as Granny Smith, Cleo–Sunrise, and Wallaby, are within this conglomeratic unit. Sedimentation occurred after the earliest deformational event.

Little is known about the internal structure and age relations in this terrane, although stacking on east-dipping thrust faults is identifi ed from mesoscopic structures (Swager, 1995a), as well as from the crustal-scale features evident in recent seismic transects (Goleby et al., 2003).

A narrow selvage of greenstones at the southeastern-most extremity of the Edjudina terrane is notable. This greenstone association includes tholeiitic basalt, komatiite with substantial komatiitic basalt, and felsic volcaniclastic sequences that appear to young to the west. The northeasternmost part of the terrane is the Merolia greenstone belt of Griffi n (1990a), which comprises mafi c and ultramafi c rocks overlain by volcaniclastic and felsic volcanic rocks, with some BIF. The area is notable for the extensive Diorite Hill layered noritic intrusive complex (12 × 8 km) and the Hanns Camp foliated porphyritic syenite — the largest (13 × 2 km) syenitic intrusion of the EGGGT.

Farther north, the Cosmo Newbery greenstone belt (Fig. 3) has a uniformly steep eastward dip, is surrounded entirely by monzogranite, and consists predominantly of basaltic rocks, with tremolitic schist on the western margin. No age data are available.

Norseman terrane

The Norseman terrane, a 27 × 60 km area in the southern-most part of the EGGGT (Fig. 3), has a well-defi ned, west-younging stratigraphy. At the deepest level, the Penneshaw Formation consists mainly of amphibolites and massive to pillowed basalts, with minor felsic volcanic rocks. Nelson (1995) obtained an age of 2930 ± 4 Ma for rhyolite in the Penneshaw Formation, confi rming an earlier age of 2938 ± 10 Ma (Campbell and Hill, 1988; Hill et al., 1989). The rhyolite contains clustered xenocryst populations of 2977 ± 9 and 3106 ± 13 Ma (Nelson, 1995), with single grains having ages as old as c. 3450 Ma (Hill et al., 1989).

The overlying Noganyer Formation is characterized by laterally continuous BIF layers within clastic sedimentary rocks, and is intruded by gabbro sills. The Noganyer


Formation is succeeded by the Woolyeenyer Formation, which is a monotonous sequence of massive basalt fl ows with a minor ultramafi c component. Hill et al. (1992) obtained a minimum age of 2714 ± 5 Ma from a fractionated intrusion, and although this sequence is apparently 10 km thick, shear zones may represent thrust faults and hence stratigraphic duplication.

Tectono-stratigraphy of the Southern Cross Granite–Greenstone Terrane

Illaara greenstone belt

The central part of the Illaara greenstone belt (Griffi n, 1990b) is within the East Yilgarn database area (Fig. 3). Wyche (1999) and Wyche et al. (2001) noted that the stratigraphy in the belt, which dips and youngs westward (Kriewaldt, 1970; Stewart et al., 1983), is distinct from the EGGGT. From the base upward, the stratigraphy comprises sandstone, quartzite, and BIF, overlain by tholeiitic to komatiitic basalt and komatiite, with an upper, poorly exposed sequence of felsic to intermediate volcanic and volcaniclastic rocks. Thin BIF and chert units become less common up sequence. The base of the sequence is intruded by granite and is tectonized. On the western side of the belt, a sequence of tholeiitic basalt with minor interbands of chert, BIF, and shale is exposed, but is in faulted contact with the eastern side, and their stratigraphic relationship is unclear. Wyche (1999) noted lateral variation in the lower part of the stratigraphy, particularly in the quartzite that lenses out to the south. Wyche et al. (2001) noted that correlation of the Illaara greenstone belt with other greenstone belts of the SCGGT to the west cannot be made with certainty. Detrital zircons from the lowermost quartzite unit indicate a maximum depositional age of c. 3300 Ma (Wyche et al., 2004).

Mount Ida greenstone belt

The Mount Ida greenstone belt (Fig. 3) has two segments. The eastern segment contains mafi c to ultramafi c volcanic and intrusive rocks, and is part of the EGGGT. The western segment is dominated by a thick sequence of tholeiitic basalt with common BIF units, typical of the SCGGT (Wyche, 1999). The Ida Fault, as defi ned farther south, is interpreted to continue north-northwesterly through these greenstones.

Granites and granitic gneissesGranites and granitic gneisses occupy more than 70% of the EGGGT. Although mainly consisting of biotite(–hornblende) monzogranite and lesser granodiorite, intrusions of trondhjemite and syenogranite, minor quartz diorite, tonalite, monzonite, two-mica(–garnet) syenogranite, and syenite are also recognized.

There are two styles of granite intrusion (Sofoulis, 1966; Perring et al., 1989). Internal granite plutons, pods


Table 2. Characteristics of granite groups in the Eastern Goldfi elds

Group Lithologies Geochemistry/abundance Petrogenesis

High-Ca Monzogranite, granodiorite, High Na2O; low Th, LREE, Zr; Rb/Sr Deep crustal (garnet stable) or slab melting>60% trondhjemite low; mostly Y-depleted with assimilation of crust and SiO2 68–77 wt% fractionation; older crust essential

Low-Ca Syenogranite, monzogranite, Low Al2O3, CaO, Na2O, and Sr; higher Reworked crustal source — Archaean TTG;>20% minor granodiorite HFSE and LILE than high-Ca group; variable partial melts by dehydration; high SiO2 70–76 wt% temperatures at moderate crustal depth

High-HFSE Syenogranite, monzogranite, Enriched in TiO2, MgO, total FeO, Y, Pre-existing crustal rocks at moderate depth;5–10% minor granodiorite; associated Zr, and Nb; CaO and K2O contents similar possible partial melt of tholeiitic source or with felsic volcanic centres to low-Ca group; LILE moderate to low; crustally contaminated fractionated tholeiite SiO2 >74 wt% magmas

Mafi c Diorite, granodiorite, tonalite, Variable silica content, subdivided by Crustal- and mantle-derived sources 5–10% monzogranite, trondhjemite variations in the LILE and LREE contents; required SiO2 50–70 wt%

Syenite Syenite, monzonite, quartz High alkali content, abundance of other Dominantly crustal origin? Possible<5% syenite, alkali-feldspar syenite elements varies; negative Nb, Ti anomalies metasomatized mantle source with crustal SiO2 55–73 wt% contribution

SOURCES: Champion and Sheraton (1997); Champion and Cassidy (2002)NOTES: TTG: tonalite–trondhjemite–granodiorite LREE: light rare earth element HFSE: high fi eld-strength element LILE: large-ion lithophile element

1

or dykes are of limited extent and entirely surrounded by, or marginal to, greenstones. External granites form extensive composite batholiths that make up the typically fault-bound elongate domal areas separating the greenstone belts. Classification schemes have endeavoured to relate these rocks to deformational events on the basis of fi eld characteristics, with subdivision into gneisses, and pre-, syn-, and post-kinematic granites (e.g. Bettenay, 1988). Witt and Swager (1989b) suggested a three-fold subdivision into pre- to syn-D2, post- to syn-D3, and post-tectonic classes — a system that could not be applied because of the varied effects of the orogenic events affecting the granites (Weinberg et al., 2003). For the purposes of their geochemical study, Witt and Davy (1997) recognized two main groups: pre-regional folding granitoid (pre-RFG) complexes, commonly forming composite cores to F2 anticlines, and circular to ovoid post-RFG plutons.

Noting the considerable overlap in geochemical characteristics of granites with very different structural characteristics, Champion and Sheraton (1997) argued that complex structural relations prevented the subdivision ofthe granites using fi eld characteristics. This has been supported by ongoing SHRIMP isotope studies of thegranites (e.g. Hill et al., 1992; Nelson, 1995, 1996, 1997b,2000; Fletcher et al., 2001), which indicate that granite magmatism was essentially continuous between 2.72 and 2.63 Ga, but with peak emplacement between 2.68 and 2.65 Ga, spanning D1 and D2. Late plugs and dykes of alkaline granite commonly yield emplacement ages between 2650 and 2635 Ma, and are considered to be

* HFSE: high fi eld-strength element† LILE: large-ion lithophile element

2

post-tectonic, providing a minimum age for the regional deformation.

More recent classifi cation schemes have concentrated solely or partly on geochemistry and petrological characteristics (e.g. Champion and Sheraton, 1993, 1997; Witt and Davy, 1997). The geochemical classifi cation scheme used by Champion and Sheraton (1993, 1997), and Champion and Cassidy (2002), combined with available SHRIMP zircon geochronology data, appears to better constrain the actual timing of the major deformation events and provides important constraints on tectonic develop-ment of the region. Champion and Sheraton (1993, 1997) broadly subdivided the granites and gneisses of the EGGGT into two major (high-Ca, low-Ca) and three minor (high-HFSE*, mafi c, and syenitic) granite groups (Table 2; see Champion and Cassidy, 2002, for a detailed discussion of the granite groups and their geochemistry). The growing geochronological database for these granites clearly shows that there were distinct time periods characterized by specifi c granite magmatism (Champion and Cassidy, 2002). In particular, there is a pronounced change in type and style of magmatism at c. 2655 Ma, from voluminous, dominantly high-Ca granites to less voluminous, but widespread, low-Ca granites. Champion and Cassidy (2002) invoked a transition from an arc-related environment to one dominated by extension or post-tectonic relaxation.

Geochemical characteristics of the EGGGT granites are typical of I-type granites, although the syenitic rocks are A-type. Most of the granites (the pre-2655 Ma, high-Ca group of Champion and Sheraton, 1997) have the chemical compositions of a LILE†-enriched variant of the typical Archaean tonalite–trondhjemite–granodiorite (TTG)


1

suite. Such rocks, the transitional TTGs of Champion and Smithies (2001), were most likely derived by high-pressure melting (garnet in the source) of a broadly basaltic precursor (e.g. Martin, 1994), within either thickened crust or a subducting slab with an additional, signifi cant, crustal input. Witt and Davy (1997) suggested hydrous melting of tonalite, granodiorite, and monzogranite in a layered lower crust to generate such granites. The subordinate later granites (post-2655 Ma, low-Ca granites of Champion and Sheraton, 1997) were probably derived by melting of a more uniform tonalitic to granodioritic mid-crustal source.

Witt and Davy (1997) also invoked fractional crystallization of biotite, feldspar, and, in the more mafi c magmas, hornblende, as the cause of some compositional variations within the granites. There are some rare- metal-enriched pegmatites (e.g. at Londonderry) that probably represent incompatible-element enrichment of the fi nal magmatic phase in the granites, but the general characteristics do not favour the formation of genetically related metalliferous deposits.

There is also evidence that the regional and temporal variations in granite geochemistry refl ect variations in the basement, both in space and time. Wyborn (1993) showed that many granites have trace element patterns that require garnet in their source rocks, whereas others have characteristics indicating stable plagioclase. Champion and Sheraton (1997) found that progressive changes in Nd-isotope ratios of the granites refl ect variations in the age of their source, becoming older to the west, whereas Smithies and Witt (1997) suggested the presence of a distinct basement terrane in the southeast EGGGT on the basis of the granite chemistry in that region. Similarly, the predominantly I-type compositions of the EGGGT granites probably refl ect an absence of large sedimentary accumulations in the middle to lower crust.

Deformational historyThe explanatory notes for the published maps provide the details of structures mapped in the fi eld or interpreted from lithostratigraphic and geophysical constraints. Summaries of the interpretations were provided in the volumes that accompanied the three stages of the EYGD (Groenewald et al., 2000, 2001; Painter et al., 2003). Recent advances by Chen et al. (2001), Weinberg et al. (2003), and Blewett et al. (2004) complement an integrated summary provided by Swager (1997).

Broadly, the recognized deformation involved early D1 recumbent folding and thrusting, followed by east–west shortening through large-scale upright D2 folding, then a period of transcurrent D3 faulting with associated folding, followed by continued regional D4 transcurrent, oblique and reverse faulting; early, intermediate, and late periods of extension have also been identifi ed (Table 3). The recent publications represent developments from the progressive sequence of D1 to D4 to a more integrated understanding of the deformation history. Only the basic fi ndings of the research are noted in this section and reference to the cited publications is advised.


3

In the southern EGGGT, Weinberg et al. (2003) examined the established structural scheme and endeavoured to place consistent age constraints on the tectonic events. An early extensional event (a period during which the major extrusive events occurred) pre-dated a transition to D1 crustal shortening between 2681 and 2672 Ma and involved thrust stacking and stratigraphic duplication. This was succeeded by D2e extension, during which subsidence allowed accumulation of the deep-marine basin deposits, as well as the late-stage Kurrawang Formation, before 2655 Ma. Then D2 followed, as a prolonged period of shortening that overlapped deposition of the late-stage sedimentary rocks. Weinberg et al. (2003) identifi ed D3 and D4 transcurrent deformation events that followed on from D2 as part of the same progressive event, 20–30 million years in duration, and named this the Kalgoorlie Orogeny.

The structural framework in the northeastern EGGGT was studied by Chen et al. (2001), who attributed it largely to transpression. Although recognizing that earlier deformation probably had considerable effects on the regional tectono-stratigraphy, these authors found the dominant mappable structures to be the result of a progression from dominant shortening to transpressional deformation during D2 and D3. The major sinistral strike-slip event on north-northwesterly trending regional faults followed the regional D2 shortening and folding. The westerly directed stress led to transpression on the north-northwesterly aligned faults. This required accommodation in the form of right-stepping restraining jogs, where compressional offset produced north-northeasterly trending folds and reverse faulting characteristic of the Laverton, Duketon, and Yandal greenstone belts, which probably owe their preservation to being within these large-scale structural domains.

In the northeastern Eastern Goldfi elds, Davis and Maidens (2003) proposed that late D2 shallow-dipping structures were much more widely distributed than previously recognized. They ascribed these to late extensional tectonism, during gravitational collapse late in the D2 crustal-thickening process, similar to that invoked by Swager (1997) for the areas farther south. Davis and Maidens (2003) invoked high temperatures associated with granite emplacement at this time to promote thermal weakening. Zones affected by the gravitational collapse may be limited in extent, and their association with pre-existing major structures is likely to make recognition diffi cult in areas where good exposure is absent.

The interpretation of the Leonora–Neal seismic traverse (Goleby et al., 2003) and attention to the three-dimensional regional geology have contributed towards a synthesis of the structural history. The east-northeast–west-southwest shortening event, which affected all of the EGGGT, involved widespread and regionally diachronous stages of compression and extension (Blewett et al., 2004). The early part of D2 involved shortening, with the formation of macroscopic faults and folds. Subsequent compression–extension switching allowed the formation of the late-stage conglomeratic sedimentary rocks in depositional basins that formed between stages of east-northeast – west-southwest shortening. These authors postulated


WA

NG

KA

TH

AA

OR

OG

EN

Y(t

)

Table 3. Summary of proposed regional deformation events in the Eastern Goldfi elds Granite–Greenstone Terrane, with age constraints provided by inferred magmatic crystallization dates

Event Structures Locality or example Timing constraint

?De Low-angle shear on granite–greenstone Lawlers; Mount Malcolm Pre-De felsic ash interbedded with contacts; north–south movement; (central Eastern Goldfi elds) komatiites c. 2705 Ma(n); early granites synvolcanic granites(a); polydirectional c. 2680 Ma extension; local recumbent folding(b)

D1 D1c Low-angle thrust faults and recumbent Between Kalgoorlie and Democrat Felsic volcanic rocks

folds(c,d,j); ?shear on early granite– (south of Kambalda) 2681 ± 5 Ma, 2675 ± 3 Ma (n)

greenstone contacts; late synvolcanic maximum age constraint; 2674 ± 6 Ma slides caused by uplift?(a,b)

post-D1 felsic porphyry dyke(q)

D1e Deformed contacts between early Jeedamya–Kookynie area

granitoid complexes and greenstones; north–south lineations in contact zone; recumbent folds in overlying greenstones(e)

De Roll-over anticlines and east–west Kurrawang, Penny Dam, Merougil Post-D1 and pre-D2 felsic porphyry; extension leading to clastic infi ll of conglomerates 2674 ± 6 Ma(q)

synclinal basins(f,g)

D2 Upright folds with shallowly plunging, Kambalda Anticline, Minimum: 2660 ± 3 Ma(n) (post-D2

north-northwest fold axes(c,e,h) Goongarrie – Mount Pleasant monzogranite) anticline, Kurrawang syncline maximum: 2655 ± 6 Ma (pre-D2

Kanowna Belle porphyry(s))

De Local extension in fi nal uplift of Barrett Well (Yabboo) Maximum: 2675 ± 2 Ma(i) (post-D1

granite domes(i) monzogranite)

D3 Tightening of F2 folds(k,l); northwest to Boorara–Menzies Fault(e,k); Minimum: 2658 ± 13 Ma(n)

north-northwest sinistral strike-slip faults Boulder–Lefroy Fault(l,c); Monzogranite at Brady Well; and shear zones; north to north-northeast Butchers Flat Fault(e) 2640 ± 8 Ma(n) (Clark Well dextral strike-slip faults and shear zones Monzogranite)

Transpression on north-northwest faults, Laverton, Yandal (central and with compressional jogs and fold axes northeast Eastern Goldfi elds) trending north to north-northeast(m)

Late D3 Steeply plunging lineations on strike- slip faults Goongarrie, Bardoc Tectonic Zone(e); Steeply dipping reverse faults Melita, Niagara(e)

De Post-metamorphic orogenic collapse(r) Ida Fault Late-tectonic granite c. 2640 Ma(r)

D4 Northwest to west-northwest oblique sinistral(e) Paddington area; 2638 ± 26 Ma(o); 2651 ± 5 Ma(p)

faults; northeast to east-northeast oblique Mount Charlotte (Kalgoorlie); post-tectonic alkaline granites dextral–reverse faults(e,j)

Black Flag Fault (Mount Pleasant)

D5 Open northeast-plunging folds, clockwise Southeast of Mount Belches Overprint caused by Mesoproterozoic rotation of earlier fabrics, steep cleavage orogenic belt parallel to Albany–Fraser Orogeny(u)

SOURCES: (a) Hammond and Nisbet (1992) (h) Hunter (1993) (o) Hill et al. (1992)(b) Passchier (1994) (i) Swager and Nelson (1997) (p) Nelson (1995)(c) Swager and Griffi n (1990) (j) Archibald et al. (1981) (q) Kent and McDougall (1995)(d) Gresham and Loftus-Hills (1981) (k) Swager et al. (1995) (r) Goleby et al. (1993)(e) Witt (1994b) (l) Swager (1989b) (s) Ross et al. (2004)(f) Williams (1993) (m) Chen et al. (2001) (t) Blewett et al. (2004)(g) Swager (1997) (n) Nelson (1997a) (u) Jones (2003)

14


1

that this overall compressive event had a progressive effect across the entire eastern Yilgarn Craton and named it the Wangkathaa Orogeny. Further implementation of this model may allow greater understanding of the fault structures, fl uid fl ow, and dilational traps that will assist modelling of the gold mineralization processes.

The youngest deformation of the Archaean greenstones, D5, recognized only in the southeasternmost Eastern Goldfi elds region, was attributed by Jones (2003) to the Albany–Fraser Orogeny. In this area, D5 is characterized by northeast-striking foliation and shallowly to moderately northeast-plunging open folds, parallel to the boundary with the adjacent Albany–Fraser orogenic belt.

Tectonic settings and modelsThe considerable research devoted to interpretation of the tectonic settings in which the Yilgarn Craton and EGGGT originated is beyond the scope of this Report. The constraints documented for the EGGGT by Barley et al., (1989), Champion and Sheraton (1993), Passchier (1994), Swager (1997), Morris (1998), Lesher and Arndt (1995), Brown et al. (2001), and several other researchers were listed in Groenewald et al. (2000, 2001, 2003). Further details will become available from AMIRA* project P437A and others when the confi dentiality controls on these studies expire in 2004.

Archaean geologyThis section contains brief descriptions of the major rock types of the EGGGT. A detailed description of each rock type is beyond the scope of this volume, but all rock code defi nitions used are listed in Appendix 1. More details are available in the explanatory notes produced for the individual 1:100 000-scale maps listed in Table 1.

In this East Yilgarn database, rock codes and code defi nitions have been modifi ed according to a revised rock-classifi cation system introduced by GSWA in 2004 (Tyler et al., in prep.). The codes are provided in database format and lack typescript settings (e.g. small capitals) as used in published GSWA maps. The revised rock codes and lithological defi nitions are listed in a conversion table attached to the database, in which each new rock code and defi nition is given with a list of the published codes on the original maps that it replaces. This has also been published as GSWA Record 2004/13 (Riganti and Groenewald, 2004). Note that in some areas codes were introduced or modifi ed from those on original published maps in the course of ground-truthing required for the seamless collation of the database.

All Archaean rocks in the EGGGT have undergone at least very low to low-grade metamorphism. However, primary textures are commonly preserved and protoliths

* AMIRA International (formerly Australian Mineral Industries Research Association Ltd) has coordinated numerous industry-funded research projects into tectono-stratigraphic, petrogenetic, and metallogenic aspects of the Eastern Goldfi elds region.

5

can be inferred in most instances. For this reason and in order to facilitate conversion to the new GSWA rock-classifi cation system, a protolith code was retained for most of these rock types, whereas for rocks in which metamorphic characteristics are paramount, a meta-morphic code was introduced.

Archaean rock types

Ultramafi c volcanic and subvolcanic rocks

Ultramafic rocks form a small, but widespread and signifi cant, proportion of the greenstone belts in the EGGGT, and several publications provide comprehensive descriptions of these rock types (e.g. Hill et al., 1990, 1995, 2001). In the area covered by the database, about 6.5% of Archaean supracrustal rocks are ultramafi c, with the most extensive outcrops in the Kambalda, Bulong, Ora Banda, Kurrajong, Mount Clifford – Marshall Pool, Leinster – Mount Keith, Murrin Murrin, and Wildara areas (Figs 2 and 3; Appendix 4).

These include undivided metamorphosed ultramafi c rock (A-mu); chlorite schist (A-musc), talc–carbonate schist (A-musk), tremolite schist (A-musr), and talc–chlorite schist (A-must); serpentinite (A-mut); komatiite with relict olivine-spinifex textures (A-uk) and pillows (A-uko), and carbonatized equivalents (A-mukk); peridotite (A-up); dunite (A-uu); and pyroxenite (A-ux). Hill et al. (1990, 1995, 2001) identifi ed most of these rock types as the products of fractionation in komatiitic volcanic fl ow fi elds. Although interlayering of dunitic to pyroxenitic rock types is common in layered intrusions, in the EGGGT such assemblages are closely associated with extrusive rocks, and are thus likely to represent products of fractionation in infl ated or ponded fl ows or subvolcanic sills. The ultramafi c rocks commonly form concordant lenses or sheets within the greenstone sequences, and carry up to 10% magnetite as a byproduct of serpentinization. Unless the rocks have undergone carbonatization or other metasomatic alteration, this magnetite content induces high magnetic susceptibility and, hence, identifi able anomalies on magnetic maps for many of the ultramafi c units. This makes it easier to interpret the extent of the supracrustal sequences concealed beneath regolith.

Deeply weathered, highly altered, and intensely deformed ultramafi c rocks are classifi ed as ‘undivided’ (A-mu) because protoliths cannot be determined with certainty. A secondary silica caprock (_R-z-u) is associated with the ultramafi c rocks at some localities, and elsewhere they are variably ferruginized. Fine-grained chlorite schist (A-musc) is largely confi ned to subsurface occurrences. Tremolite schist (A-musr) is fi ne to medium grained, and mainly composed of tremolite needles or blades up to 10 mm long. The microstructural fabric varies from a completely random orientation of the acicular tremolite to a planar arrangement defi ning the schistosity, and alignment as a mineral lineation. Chlorite and talc are the other main minerals, with carbonate at some localities. Talc–chlorite schist (A-must) is commonly fi ne grained and strongly schistose. Talc is dominant, chlorite varies


16

from 10 to 40%, magnetite is a common accessory mineral, carbonate varies up to 20%, and tremolite and antigorite are present in some samples. Locally pervasive carbonatization has resulted in areas of talc–carbonate(–serpentine) rock (A-musk). Intense serpentinization has locally obliterated all primary textures to produce serpentinite (A-mut), which is typically fi ne grained and composed of serpentine (20–90%), tremolite–actinolite, relict olivine, chlorite, epidote, plagioclase, hornblende, magnesite or ankerite, opaque minerals, and chalcedony. It is even grained to weakly blastoporphyritic, massive to foliated, and can locally grade into talc or chlorite–magnetite schist. Serpentinite forms elongate bodies up to several kilometres long. Protoliths for these ultramafi c rocks were probably olivine cumulates or komatiites, but cannot be identifi ed in the absence of primary igneous microstructures. Tremolite schists containing small amounts of plagioclase may represent metamorphosed equivalents of komatiitic basalt that commonly, but not necessarily, are associated with komatiites in ultramafi c sequences.

Komatiite (A-uk) is commonly identified by the olivine-spinifex texture characteristic of the upper parts of fl ow units. The dominant mineral assemblages are serpentine–tremolite–chlorite or tremolite–chlorite depending on position within the differentiated fl ow unit. Talc and magnetite are minor or accessory minerals. Primary olivine is rare and primary chromite is widespread, but in low concentrations. Although almost universally serpentinitized, olivine pseudomorphs are commonly preserved, allowing recognition of spinifex texture even in highly altered rocks. Replicas of large platy skeletal olivine crystals (commonly 50–150 mm, but up to 700 mm long) are most commonly arranged as book-like stacks, but are also randomly oriented in the upper parts of lava fl ows. In areas of low strain, relict textures in the lower part of a fl ow allow recognition of original olivine-cumulate rocks. Thus, despite ubiquitous metamorphism and alteration, original komatiitic lava fl ows have been identifi ed, with primary fl ow thickness ranging from less than a metre to more than several hundred metres. Fractionated successions in lobes of the komatiite fl ows are up to 800 m thick in total, and probably refl ect enormous outpouring of lava leading to development of great fl ow fi elds (Hill et al., 2001). A lateral extent of about 100 km has been recognized for some fl ows, with major lateral variations attributed to different sub-environments within the voluminous and regionally extensive eruptions (Hill et al., 1990). The present extent of these fl ow fi elds is represented in the database region by the extensive peridotite outcrops described below. Pillowed to massive komatiite (A-uko) and extensively carbonatized komatiite (A-mukk) have been mapped locally as separate units.

Peridotite (A-up), the ultramafic rock type that outcrops most extensively, has assemblages of serpentine, amphibole, chlorite or talc, typically preserving textures that reveal the original mineralogical and cumulate characteristics. The original matrix has been altered to a fi ne-grained mass of tremolite, chlorite, serpentine, and magnetite. Primary igneous olivine has survived very low metamorphic grades at a few localities (e.g. Bulong Complex), and metamorphic olivine has crystallized in cumulates metamorphosed at amphibolite facies (Hill

et al., 1990). Cumulate textures may also be preserved in the ferruginous silica caprock that commonly developed above peridotite during the weathering process.

It is notable that, when seen in isolation, the cumulate lower portion of a komatiite fl ow is indistinguishable from the peridotites attributed to layered intrusions, and correct interpretation of an intrusive or effusive origin requires recognition of the geological context. Peridotite in the Mount Clifford – Marshall Pool area, about 50 km north of Leonora in the southernmost extent of the Agnew-Wiluna greenstone belt, is overlain by spinifex-textured fl ows and represents extensive ultramafi c volcanic complexes. Similarly, several exposures of spinifex-textured rock in the Kilkenny Syncline on MINERIE* indicate that the extensive surrounding peridotites represent differentiated komatiitic lava fl ows. Preserved cumulate textures are abundant in the lower part of the regionally extensive komatiite unit in the Ora Banda area (the Walter Williams Formation of Hill et al., 1990, and Witt, 1994b). The Bulong Complex in the Gindalbie area (KANOWNA) represents another substantial accumulation of ultramafi c lava, of which a significant proportion consists of serpentinitized cumulate rocks (Ahmat, 1993).

Dunite (A-uu) is commonly associated with komatiite in differentiated fl ows, and is distinguished by adcumulate to mesocumulate textures. It is best exposed on DUKETON, but is present in the subsurface on WILUNA, MOUNT KEITH, and SIR SAMUEL.

Pyroxenite (A-ux) is associated with the large differentiated komatiitic flows (e.g. Bulong) and mafi c–ultramafi c subvolcanic sills, in which pyroxenite may amount to 50% by volume. These rocks are readily recognized in domains where penetrative foliation is not well developed and pseudomorphism of primary pyroxenes by metamorphic amphibole is preserved. Deformed and more strongly recrystallized samples contain moderate to large amounts of chlorite and talc. Pyroxenite also makes up a large portion of the Carr Boyd Rocks Complex near the northernmost greenstones of the Gindalbie terrane. The complex includes layered ultramafi c to mafi c sequences (recognized in drillcore; Purvis et al., 1972), crosscut by bronzitites that outcrop over several square kilometres as tremolite and tremolite–chlorite rocks with preserved cumulate and pegmatoidal textures.

Mafi c volcanic and subvolcanic rocks

About half of the greenstone sequences consists of mafi c extrusive rocks. Both tholeiitic and komatiitic types are present, but may be indistinguishable in the fi eld because characteristic textures are not always preserved. Hence, massive, fi ne to very fi ne grained mafi c rocks (A-b) that have not been subdivided are mainly tholeiitic basalts, but may include intercalations of komatiitic basalt. These rocks are commonly deeply weathered.

The extensive outcrops of tholeiitic basalt (A-bb) in all greenstone belts amount to about 70% of all mafi c volcanic

* Capitalized names refer to standard 1:100 000 map sheets, unless otherwise indicated.


17

rocks. This rock type is typically equigranular, very fi ne to fi ne grained (but locally medium or coarse grained), and composed of blue-green actinolite, plagioclase, and opaque minerals (ilmenite and magnetite). Other minerals present locally include green hornblende instead of actinolite, epidote after plagioclase, hematite, quartz, carbonate, and titanite. They are typically massive rocks, but may be amygdaloidal (A-bbg) or porphyritic (A-bbp), and locally aphyric (A-bba). Pillow structures and fl ow-top breccias are rarely exposed or poorly preserved. In some areas, basaltic rocks show a pronounced range in grain size and textures, with interleaved units of fi ne-grained subophitic basalt and coarser dolerite–gabbro (A-bby), which may locally be porphyritic (A-bbq). These units are most probably the products of crystallization and differentiation within thicker, possibly ponded, fl ows or may indicate the presence of numerous subvolcanic intrusions. These rocks make up extensive parts of the greenstones on MOUNT ALEXANDER, southeast MINERIE, and MCMILLAN. On southeastern COSMO NEWBERY, outcrops of tholeiitic basalt extend over 70 km2. On NORSEMAN highly texturally variable basaltic rocks, including basaltic fl ow units such as those described above, pillow basalts, and subvolcanic gabbroic sills cannot be subdivided at 1:100 000 scale (A-bn). In the Gindalbie terrane, basaltic rocks form a bimodal sequence with interlayers of rhyolite and dacite (A-xbb-f).

Coarsely porphyritic basalt (A-bbp) has plagioclase phenocrysts ranging from 2 to 30 mm in length, locally in glomeroporphyritic clusters, set in a fi ne- to medium-grained hornblende and plagioclase matrix. The porphyritic basalt forms stratigraphic marker units that can be recognized in areas of otherwise indeterminate bedding. For example, a 5 km-long unit marks the only recognized bedding in a 5 km2 area of basalt–dolerite (A-bby) on northwestern LEONORA. In the northern Ora Banda domain of the Kalgoorlie terrane (Fig. 3), porphyritic basalt with tabular plagioclase crystals up to 3 cm in length forms a distinctive unit up to 2 km thick at the top of the upper basalt, whereas a similar unit lies within the lowermost basalts in the southern Coolgardie domain .

Amygdaloidal basalt (A-bbg) is readily distinguished from very fi ne grained, nonvesicular tholeiitic basalts. There are extensive outcrops of amygdaloidal basalt in the Mount Clifford greenstone belt on WEEBO, Malcolm greenstone belt on YERILLA, Murrin greenstone belt on MINERIE, and the Laverton greenstone belt. Pillow basalt (A-bbo) is present at many localities, but is not widely recognized, probably because of the generally poor exposure and deformation that in some areas mask such structures. Pillow basalt can be locally variolitic (A-bbd) and can have pyroxene-spinifex texture. Variolitic basalts that are not pillowed have been coded separately (A-bbw). Variolitic basalts typically consist of a fine, felted groundmass of acicular amphibole(–chlorite) and subordinate (up to 30%) very fi nely recrystallized plagioclase, with abundant pale, spherical to ovoid cryptocrystalline varioles (termed ocelli on some published maps) that range in diameter from 1 mm to more than 1 cm. Varioles are mineralogically similar to the groundmass in which they formed, but contain a greater proportion of plagioclase. Variolitic textures are


commonly, but not universally, indicative of high MgO content (i.e. in the komatiitic basalt range).

Basaltic fragmental rocks (A-bbx) are a minor component of greenstone sequences, and may include agglomerate, hyaloclastite, peperite or breccia. Basaltic tuff (A-bbt) has been identifi ed only on GINDALBIE.

Basaltic andesite (A-bd) and distinctly feldspar-phyric equivalents (A-bdp) are pale-green to grey-green, fi ne-grained, massive to pillowed rocks, which are commonly exposed as rounded cobbles and boulders, with well-preserved pillows at several localities. Amygdales are common in most exposures, whereas larger gas pipes and cavities that locally coalesce into irregular breccia zones cemented by quartz may represent fl ow tops. Basaltic andesite consists of plagioclase, tremolite–actinolite, rare chlorite, and accessory titanite or leucoxene in a fi ne-grained groundmass containing abundant plagioclase microlites. Basaltic andesite outcrops extensively on northeastern MELITA.

Pyroxene-spinifex-textured basalt (A-bs) represents only about 2% of the exposed Archaean supracrustal sequences and about 5% of the basaltic rocks, but it is one of the most distinctive mafi c rock types within the greenstone sequences. These rocks usually have a characteristic composition of 10–18 wt% (anhydrous) MgO, and on most maps were originally described as high-Mg or komatiitic basalt. Grey to pale-green tremolite–actinolite is the main constituent, with up to about 30% plagioclase, accessory amounts of opaque oxides (typically magnetite), and secondary chlorite. The common relict pyroxene-spinifex texture consists of tremolite–actinolite pseudomorphs after acicular clinopyroxene that range from a few millimetres to several centimetres in length. Clusters of pseudomorphs can assume dendritic or fan-like forms. Pyroxene spinifex-textured basalt fl ows vary laterally in physical characteristics, with spinifex textures completely absent from substantial portions in some sections. Although pillow structures are present, these are rarely well exposed in surface outcrop and are probably obscured by deformation in many areas. Varioles are locally developed.

In the southern Kalgoorlie terrane, pyroxene spinifex-textured basalt is at two lithostratigraphic levels: near the base of the lowermost mafi c volcanic unit in the Kalgoorlie sequence and at low levels in the basaltic unit above the komatiite unit. In the northern part of the terrane (on northwestern WILDARA), relatively unaltered basalt exposed in the eastern limb of the Lawlers Anticline is characterized by coarse pyroxene spinifex, as well as pillow structures that, although poorly exposed, indicate northeasterly younging of steeply northeasterly dipping fl ows. Farther south on LEONORA, outcrops of pyroxene-spinifex-textured basalts east of Mount Stirling reveal several individual fl ows that are defi ned by their pillowed fl ow tops. The fl ows range from 100 to 300 m in thickness, and vary in grain size from gabbroic patches to glassy zones at the fl ow margins. The bulk of each fl ow is medium grained and equigranular. On southeastern BALLARD, pyroxene-spinifex-textured basalt forms the upper portion of the ultramafi c sequence described by Hill


18

et al. (1995) in the Kurrajong Anticline and the Snake Hill Syncline to the south. Pyroxene spinifex-textured basalt is associated with peridotite in extensive areas around the Kilkenny Syncline in the Murrin greenstone belt. In the Laverton greenstone belt, pyroxene spinifex-textured basalt is exposed 5 km south-southeast of Mount Varden and east of Mount Margaret Mission.

In many areas, basaltic rocks have been variably deformed, metamorphosed, and metasomatized. Foliated fi ne-grained mafi c rocks (A-mbs) have been distinguished from fi ne-grained basaltic schist (A-mbbs) and foliated spinifex-textured basalt (A-mbps). In different areas, metamorphism and metasomatism have produced basalt and basaltic andesite that have been epidotized (A-mbbd, A-mbdd), carbonatized (A-mbbk, A-mbdk), and hornfelsed (A-mbbe). Where basaltic rocks are completely recrystallized and no vestiges of primary textures remain, they are classifi ed as amphibolite (A-mbba). Prismatic amphibole and fi ne-grained, polygonal granoblastic plagioclase with little or no twinning are the main constituents. Clinopyroxene is present locally. Compositional variations are reflected by different proportions of plagioclase relative to amphibole.

In zones of strong shearing and deformation, amphibolite and basaltic schist are interleaved with meta-sedimentary rocks (A-xmbba-md, A-xmbs-md) and felsic schist (A-xmbbs-mfs). Packages of foliated, interleaved greenstone and granitic layers (A-xmb-mg) are up to 1.5 km wide (e.g. west of the Yandal greenstone belt). Individual layers of greenstone or granite up to 50 m thick defi ne low, narrow, north-northwesterly trending ridges. Local gneissic banding is defi ned by segregation of mafi c and felsic minerals.

Mafi c volcanic rocks — named

The Mount Goode Basalt (A-_mg-bb; Liu et al., 1998) contains an extensive suite of massive, fi ne-grained tholeiitic metabasalt in the Agnew–Wiluna greenstone belt, north of Lake Miranda on SIR SAMUEL. The upper part of the Mount Goode Basalt is commonly porphyritic (A-_mg-bbp) with zones in which plagioclase phenocrysts form up to 15%, and occasionally 30%, of the rock. Pillow basalt, with plagioclase phenocrysts up to 20 cm across, shows strong to moderate strain in good exposures on an island in Lake Miranda.

Felsic volcanic, volcaniclastic, and subvolcanic rocks

Felsic rocks of probable volcanic and volcaniclastic origin account for about 18% of the greenstone belts. Where deep weathering hinders accurate protolith classifi cation, they are simply described as felsic rocks (A-f). These typically consist of fi ne-grained, equigranular quartz, feldspar, and biotite, and are locally porphyritic with typical phenocrysts of subhedral quartz crystals (2–6 mm in diameter) or subhedral feldspar (up to 8 mm in length), and rare biotite and hornblende phenocrysts.

Undivided felsic volcanic and volcaniclastic rocks (A-fn) have been identifi ed by clearly extrusive textures,

such as fl ow banding, embayed quartz and feldspar phenocrysts, fragmental clastic deposits, and finely layered tuffi tes. They range in composition from rhyolite to dacite and andesite, but separation into different types is impossible at 1:100 000 scale. Where individual rock types could be separated at map scale, felsic volcanic rocks have been further subdivided. These include rhyolite lava fl ows (A-fr), rhyodacite (A-fcp), and dacite (A-fd). Porphyritic felsic rocks are widespread in the felsic volcanic successions. These are typically feldspar–quartz-phyric (A-fdp) or quartz(–feldspar)-phyric (A-frp), with a fi ne-grained dacitic to rhyolitic groundmass. The rocks are typically volcanic to subvolcanic in setting and association. An unusual biotite–quartz–feldspar porphyritic body with abundant greenstone xenoliths (A-fnpi) lies within the ultramafi c sequence on BARDOC.

Felsic volcanic and volcaniclastic rocks are present in several volcanic complexes, such as Spring Well, Welcome Well, Melita, Jeedamya, Ida Hill, and Bore Well, forming much of the upper part of the volcanic and sedimentary unit of the Kalgoorlie terrane. Detailed geological and geochemical data for some of the felsic-dominated volcanic rock successions in the EGGGT have been presented by Morris (1998) and Brown et al. (2001).

The felsic rocks from the Black Flag Group* in the Kalgoorlie terrane form a dacite–rhyolite association consisting of dacite and rhyolite lavas with associated breccia, volcaniclastic sandstone, and carbonaceous shale. Some dacite and rhyolite units were extruded as subaqueous lava lobes, generally less than 10 m thick. A variety of clastic sedimentary rocks are associated with the dacite–rhyodacite porphyritic rocks, crystal and lapilli tuffs, and volcaniclastic conglomerates in upper parts of the sequence. Because of the poor exposures it is unclear whether these rocks represent primary pyroclastic deposits or epiclastic sediments. Oligomictic conglomerate, containing subangular clasts of the porphyritic felsite up to 50 cm in diameter, set in a matrix of similar composition, may be partly volcanic and partly sedimentary in origin. Other interbedded rocks, ranging from shale to pebbly sandstone to conglomerate, have sedimentary structures such as graded bedding, fl ame structures, and load casts. These structures are more common than cross-beds and ripple marks, suggesting deposition in a gravity-fl ow rather than stream-fl ow environment. Some shale and chert units may represent fi ne ash-fall deposits.

The distribution of felsic fragmental and pyroclastic rocks in the database area is relatively restricted, particularly as mappable units. Tuffaceous rock (A-frt) is fi nely banded and fi ne to medium grained, and contains quartz and feldspar phenocrysts. Almost all exposures of this rock type are on MINERIE, BURTVILLE, and YILMIA. Units on DARLOT that contain massive to laminated bands, 2–10 cm thick (average 4 cm), and local graded beds were interpreted to be pyroclastic fall deposits (A-frvt; Westaway and Wyche, 1998). Volcaniclastic rocks ranging from andesite to basaltic andesite in composition and

* Identifi cation of all outcrops that may be ascribed to the Black Flag Group and appropriate coding have not been completed.


19

with common fragmental textures (A-fnv) are common in the southern part of the EGGGT and in the Spring Well Complex farther north. Felsic volcanic breccia in the Spring Well Complex is poorly sorted, matrix supported, lacks internal stratifi cation, and contains a range of volcanic clast types (Westaway and Wyche, 1998). Other felsic rock types mapped in the complex include lapilli tuffs (A-frth), plagioclase or quartz-porphyritic rock (A-fdp), and fi ne-grained andesitic basalt units (A-bd — possibly intrusive; Wyche and Westaway, 1996; Giles, 1980, 1982). Massive to poorly bedded, rhyolitic to rhyodacitic oligomictic breccia and tuff, with lithic clasts (>1 cm) in a fi ne-grained to glassy matrix (A-frxl), and mixed rhyolitic to trachytic tuff and oligomictic breccia (A-xfrv-ftv) are exposed on MELITA.

Ignimbrite (A-frv), exposed on YERILLA, BOYCE, and LAKE CAREY, consists of quartz and feldspar crystals and lithic fragments encased in a banded siliceous matrix that retains textural evidence of welding and differential compaction around phenocrysts and clasts. Elongate hollows and some fi ne-grained quartzofeldspathic laths in these rocks are interpreted to be after fi amme, which represent pumice fragments compressed subparallel to primary layering during accumulation of the ignimbrite. The Spring Well Complex contains similar rock types, but not as map-scale outcrops.

Andesitic volcanic rocks locally make up a signifi cant proportion of the greenstone sequences. They are fi ne-grained quartzofeldspathic rocks with volcaniclastic or flow textures. Andesite (A-fa) and plagioclase(–hornblende) porphyritic andesite (A-fap) are dominant rock types in the Welcome Well Complex on MINERIE, the Ida Hill Complex on LAVERTON, and the Bore Well Complex on LAKE CAREY. Coarsely porphyritic andesite and foliated equivalents (A-mfsa) are also on YERILLA, BALLARD, and MOUNT VARDEN, and in the Murrin greenstone belt about 5 km west of Minerie Hill. A fl ow-banded trachyandesitic rock (A-fab) was recognized on LAKE VIOLET.

Andesitic volcanic and volcaniclastic rocks (A-fav) are also relatively abundant in parts of the Black Flag Group in the southern Kalgoorlie terrane. In the Ora Banda domain the uppermost part of the sequence includes porphyritic plagioclase–hornblende andesite and hornblende dacite, as well as a coarse-grained volcaniclastic conglomerate with angular to subrounded, pebble- to boulder-sized clasts, mainly of a porphyritic felsic rock. Hunter (1993) described thin beds of lapilli tuff, crystal tuff, and very fi ne grained ash deposits in this area. In the Gindalbie terrane, andesitic rocks defi ne the eastern part of the Bulong Anticline. Most of the massive andesites and andesitic basalts at this locality are altered or foliated or both. Fragmental rocks of andesitic composition, as well as minor rhyodacite, dacite, and basaltic andesite are also present. Andesitic volcanic rocks make up a substantial proportion of the greenstones in the Edjudina terrane. These rocks include dacite, andesite, and basaltic andesite that are commonly porphyritic (plagioclase, less commonly hornblende) or amygdaloidal or both. Angular clasts are locally recognizable, indicating volcaniclastic protoliths for these parts. At some localities these rocks grade into greywacke.

In areas of higher metamorphic grade, felsic rocks are foliated (A-mfss) or so strongly deformed, recrystallized, and weathered that they can only be recorded as quartz–feldspar–mica schist (A-mfs). Schists derived from andesitic and dacitic rocks (A-mfas) are recognized on LAKE LEFROY. Although those with volcaniclastic protoliths may be identifi ed because of their oligomictic nature and blastoporphyritic fragments, many quartzofeldspathic schists are of uncertain origin, with extrusive or intrusive igneous protoliths indistinguishable from immature sedimentary protoliths. In saprock variants, quartz grains are commonly enclosed by a mass of clay minerals that may or may not preserve a foliation, but remnant quartz phenocrysts display embayments indicative of a volcanogenic origin. Locally, units within these felsic schists are distinguished by the common presence of chlorite aggregates (A-mfsc) or andalusite porphyroblasts (A-mfsd).

Other volcanic and volcaniclastic rocks

Mafi c to intermediate schists with fi ne layering and small hornblende and feldspar fragments (A-mvs) recognized on YABBOO and felsic schists mapped on MOUNT BELCHES (A-mvfs) are likely to represent primary pyroclastic deposits or proximal reworked volcanic material. Carbonatized, interleaved volcaniclastic rocks (A-mvks) were recognized on BARDOC.

Chemical sedimentary rocks

Chemical sedimentary rocks form less than 3% of the outcrop area, but are exposed in all greenstone belts. Chert (A-cc), banded chert (A-ccb), and BIF (A-cib) are the dominant types, commonly forming prominent strike ridges. They typically defi ne the best available markers for remotely sensed correlation of outcrops or delineation of structures, particularly using aerial photography and magnetic imagery. Chert predominates in the EGGGT, whereas BIF predominates in the SCGGT, and this is a criterion generally used to assign greenstones to different terranes. West of the Ida Fault, on MULLINE and in the western parts of RIVERINA and DAVYHURST, the greenstones contain abundant chert and BIF, which led Swager et al. (1990) to attribute them to the SCGGT. In the Illaara and the western Mount Ida greenstone belts, BIF is very common, forming a signifi cant portion of the rock exposure, and thus these belts are interpreted to be part of the SCGGT. Banded iron-formation has not been recorded in outcrops of the Kalgoorlie terrane east of the Ida Fault, but is present as the dominant clast type in a conglomeratic unit of the Kurrawang Formation (see Sedimentary formations). Banded iron-formation becomes progressively more abundant east of Bulong, and in the Kurnalpi terrane there are a few units that extend for several kilometres along strike. In the Edjudina terrane, BIF forms narrow topographic ridges that coincide with linear magnetic anomalies about 200 km in strike length. In the Norseman terrane, BIF forms substantial units, up to 70 m thick, with strike lengths of up to 40 km. Both the Murrin and Laverton greenstone belts contain a higher proportion of BIF in the north, whereas to the south


20

virtually all chemical sedimentary rocks are chert. Chert is more common in the Duketon greenstone belt, where it is typically associated with siltstone and sandstone.

Banded iron-formation is present largely as oxide (A-cib) and silicate (A-mi) facies. The former is much more common, and outcrops as fi nely layered, fi ne-grained, quartz–magnetite rock, interleaved with chert or siliceous slate. The iron content of these rocks is highly variable, and they range from very thinly bedded to laminated, pale- to dark-grey banded chert, to grey, pink, and red ferruginous banded chert, to highly magnetic, red and black, magnetite-bearing BIF. Bedding is commonly disrupted by kinks and minor folds. Pronounced folding is characteristic, including sheath and intrafolial folds with variable orientations, possibly refl ecting components of early slumping, differential compaction, and the regional deformation. The strong magnetic signature of these units provides very distinct traces on magnetic images. Silicate-facies BIF is of limited extent, generally with a quartz–magnetite(–grunerite–hornblende) assemblage. Thin units of jaspilite (A-cij) are exposed on LAKE VIOLET, LAVERTON, and URAREY. Chert breccia cemented by goethite is exposed on LEONORA and LAKE VIOLET.

Dolomite (A-kd) is within a sedimentary sequence on WILUNA, and several exposures of limestone (A-kl) are associated with interfl ow sedimentary rocks in a basalt sequence on LAKE VIOLET, LAVERTON, and LEONORA.

Clastic sedimentary rocks

Clastic sedimentary rocks are in all the greenstone belts and amount to about 12% of the outcrop area in the EGGGT. They are typically associated with the felsic volcanic and sedimentary upper parts of the greenstone sequences, and may include a signifi cant felsic volcaniclastic component, but poor exposure and deep weathering commonly hinder protolith identifi cation. In the Kalgoorlie terrane, sedimentary rocks make up the Black Flag Group and the unconformably overlying Kurrawang Formation, whereas in the eastern terranes there is no established stratigraphic succession. In the northern EGGGT, clastic sedimentary rocks are more common in the Murrin and Duketon greenstone belts. Sedimentary structures are diffi cult to recognize, particularly in the fi ne- to medium-grained rocks, but younging and palaeocurrent indicators can be identifi ed.

Undivided sedimentary rock (A-s) or i ts metamorphosed equivalent (A-md) is either poorly exposed, deeply weathered, or contains a sedimentary rock sequence that cannot be subdivided at 1:100 000 scale. These units may include shale, siltstone, chert, sandstone, pebbly sandstone, and conglomerate (and metamorphosed equivalents) with graded bedding and cross-bedding preserved at many localities. Epiclastic felsic sedimentary rock (A-snf) also varies in grain size, and is commonly deeply weathered and kaolinized.

Shale (A-sh), commonly including subordinate chert or siltstone or both, is widespread and may be used locally as a marker unit. This rock type is common as interfl ow sedimentary units in volcanic sequences, where strain is

typically taken up by shale units so that the cleavage is either parallel, or subparallel, to compositional layering. Locally widespread (e.g. on ROE) carbonaceous to graphitic black shale (A-shh) is very fi ne grained and moderately foliated to massive, with some angular grains of quartz and feldspar set in the graphitic matrix. A shale and siltstone unit with quartz granules (A-shq) has been distinguished on DARLOT. Siltstone (A-sl) has been separated only on DUKETON. A fine-grained quartzofeldspathic rock with banded chert pebbles (A-slc), associated with banded chert, outcrops on NORSEMAN. Fine-grained sedimentary rocks may grade into micaceous quartzofeldspathic schists (A-mdfs; e.g. on PINJIN and KURNALPI) that range from fi ne to coarse in grain size. Although the foliation is commonly the only visible structure, graded bedding, scour marks, slump structures, and parallel bedding can be recognized in localized, good surface exposures. Interlayering with lithic wacke or volcaniclastic-derived rock types (or both) indicates that these rocks probably originated as distal epiclastic deposits. Metamorphosed equivalents of fi ne-grained sedimentary rocks are commonly represented by pelitic schists (A-mls) with local andalusite, kyanite, garnet, staurolite, and cordierite porphyroblasts; andalusite-bearing phyllite (A-mlpd); and grey to black slate (A-mlv) and carbonatized equivalents (A-mlvk).

All greenstone belts of the EGGGT contain some sandstone (A-st), with an abundant siltstone component (A-ss), or are closely associated with conglomerate (A-sp). The most extensive outcrops of sandstone are on KANOWNA, MELITA, and YERILLA, but minor occurrences are widespread. The sandstones are generally medium to coarse grained, but contain siltstone layers in many outcrops. Polymictic conglomerate (A-sc) is matrix or clast supported, with clasts including chert and granitic, mafi c, and felsic porphyritic rock. The most substantial sandstone–conglomerate assemblages are commonly within the late basin deposits (see Sedimentary formations). Quartzofeldspathic pebbly sandstone (A-sr), ferruginous sandstone (A-sti), and quartz-rich sandstone (A-stq) have been identifi ed locally. A metamorphosed association of poorly sorted lithic wackes (A-sw) at several localities on LAKE LEFROY forms graded units interleaved with basaltic rocks, as well as extensive outcrops on KURNALPI that probably correlate with the Mount Belches Formation to the south. Greywacke of mafi c to felsic composition (A-swb) and arkose (A-swa) are also distinguished on some map sheets.

Oligomictic conglomerates dominated by clasts of felsic volcanic rocks (A-scf) are in several of the greenstone sequences. These rocks are most abundant in the southern parts of the Gindalbie, Kurnalpi, and Edjudina terranes, although they generally have limited extent. The felsic volcanic clasts are generally less than 20 cm in diameter, although a few boulders may exceed a metre in diameter. On PINJIN and ROE, conglomerates of this type may be traced along strike from clastic through volcaniclastic to volcanic rock types. Oligomictic conglomerate with chert clasts (A-scc) has been recorded on NORSEMAN, whereas conglomerate containing clasts of quartz, quartzite, and chert (A-scq) is common in the Illaara greenstone belt, where it overlies and is interbedded with quartzite. Epiclastic conglomerate and sandstone with


21

andesitic clasts (A-sgf) are restricted to the Welcome Well volcanic complex in the Murrin greenstone belt, whereas conglomerate and pebbly sandstone with basalt and gabbro clasts (A-sgb) are more common in the northern EGGGT. Metamorphosed conglomerate with pebbles of amphibole–feldspar–quartz–garnet rock (A-mx) has been recognized on KURNALPI. Sedimentary breccia (A-sx) is an uncommon rock type.

In the SCGGT quartzite (A-mtq) forms a prominent strike ridge along the eastern side of the Illaara greenstone belt and a small exposure in the western part of the Mount Ida greenstone belt. Several other very minor exposures are recorded in the EGGGT. Foliated and mylonitic quartzite (A-mtqs) has been identifi ed on NORSEMAN. Para-amphibolite (A-mda) has been recorded on LEONORA, whereas psammopelitic rock consisting of chloritic, mafi c to felsic schist (A-mhs) was distinguished on MOUNT BELCHES.

Sedimentary formations

Although poor exposure prevents stratigraphic recon-structions in most greenstone belts, sedimentary sequences with distinct characteristics and spatial relationships have been distinguished in some belts.

The Mount Belches Formation (A-_b-s) is a mono-tonous package of metamorphosed, multiply deformed wackes (A-_b-mt) and mudstones (A-_b-ml) that outcrop extensively on MOUNT BELCHES. The formation is at least 2500 m thick and is interrupted only by the Santa Claus Member (A-_bn-sw) — a distinctive sequence of turbiditic iron-formation in the upper part of the sequence. Despite metamorphism to amphibolite facies, sedimentary structures are locally preserved in fine detail, and include common Bouma sequences, ripple marks, climbing ripple marks, channel casts, scour marks, cross-laminations, soft-sediment deformation structures, load and fl ame structures, and mudstone intraclasts, as well as localized pull-apart structures, neptunian dykes, and small-scale synsedimentary extensional faults (Dunbar and McCall, 1971; Painter and Groenewald, 2001). Graded wacke–mudstone units (A-_b-mh) have been hornfelsed (A-_b-mhe) by the intrusion of the Kiaki Monzogranite or metasomatized (A-_b-mhz). Although Swager (1995a) and Krapez et al. (2000) considered the Mount Belches Formation to be laterally equivalent to the post-D1 Penny DamConglomerate, Painter and Groenewald (2001) documented evidence for D1 deformation of the Mount Belches Formation.

The Jones Creek Conglomerate is a post-D1 sedimentary sequence, up to 1000 m thick, in the southern part of the Agnew–Wiluna greenstone belt in the northern Kalgoorlie terrane. The dominant rock type is a variably deformed polymictic conglomerate (A-_ jc-scp), and includes conglomerate and sandstone with granitic clasts and quartzofeldspathic matrix (A-_ jc-sgg), subordinate interbedded arkose (A-_ jc-sta), and, to the east, less common conglomerate with a mafi c matrix (A-_ jc-sgp). A detailed description of the Jones Creek Conglomerate was presented by Jagodzinski et al. (1999).


Coarse-grained clastic sedimentary rocks of the Kurrawang Formation outcrop sporadically for more than 80 km along the western boundary of the Ora Banda domain (Fig. 3), resting unconformably on older greenstones and occupying the core of the Kurrawang Syncline. The lower part of this formation (A-_kw-sc) consists mainly of conglomerate and pebbly sandstone. It is about 750 m thick near White Lake in the south, but thins to the north. The poorly sorted, generally matrix-supported, conglomerate contains well-rounded, commonly stretched clasts, typically 5 to 10 cm, but up to 25 cm, in length. Clasts are most commonly felsic and intermediate rocks from the underlying sequence, but there are also clasts of BIF, chert, and quartzite, and, less commonly, basalt, amphibolite, and ultramafi c rock. The medium- to coarse-grained matrix consists of poorly sorted lithic sandstone. Banded iron-formation clasts are common only in a single extensive unit (A-_kw-sci), about 30 m in thickness, that forms a magnetic marker horizon. This layer has a problematic provenance because BIF is not known in the proximal lithostratigraphy and the nearest outcrops of this rock type are those in the greenstone belts of the SCGGT, about 40 km to the west. The upper part of the Kurrawang Formation (A- kw-st) consists of medium- to coarse-grained, locally pebbly, lithic sandstone. Cross-bedding and graded bedding are common, and there is a general upward-fi ning trend.

The polymictic Penny Dam and Yilgangi Conglom-erates outcrop along major fault zones within the Gindalbie and Kurnalpi terranes respectively. These rocks have similar characteristics to those of the lower Kurrawang Formation, although clasts range more widely in size and may attain a diameter of 40 cm. The compositional range of clasts includes granite, quartz–feldspar porphyry, gabbro, chert, and minor schistose mafi c rocks. An immature fl uvial origin is suggested by the poorly sorted, poorly bedded, clast- to matrix-supported nature of these conglomerates, although wedge-shaped, faceted clasts in the Penny Dam Conglomerate suggest a possible glacigenic origin (Swager, 1993).

The Merougil Sandstone (A-_me-st) outcrops in southwestern LAKE LEFROY and consists of immature sedimentary rocks. These are mainly trough cross-bedded, pebbly sandstones, but include high proportions of conglomerate and siltstone. The beds are 2 to 300 m thick, have a polymictic clast assemblage, rest on a sheared disconformity, and are probably of fl uvial origin.

Mafi c intrusive rocks

Medium- to coarse-grained intrusive mafi c rocks, with relict cumulate, xenomorphic, subophitic, or ophitic textures, are common throughout Archaean supracrustal sequences of the EGGGT and constitute about 11% of all outcrop in the greenstone belts. Although metamorphic amphibole has commonly replaced original pyroxene, it is typically pseudomorphic and primary textures are recognizable, allowing the use of igneous terminology in most instances. Many intrusions pre-date most or all of the deformation history. Where lithostratigraphic relations are visible, the units are generally conformable, but


22

may also be locally transgressive. In many cases a close compositional similarity to associated basalts suggests a syngenetic origin, either as subvolcanic intrusions or as coarser grained portions of thick, ponded fl ows.

Deeply weathered, medium- to coarse-grained mafi c rock (A-o) is undivided. Mafi c intrusive rocks are commonly shown as gabbro (A-og) on the maps because the detail of fractionated compositions is either too fi ne for the map scale or largely obscured by poor outcrop, even though many of the intrusions show clear igneous differentiation. Of the numerous gabbroic intrusions too small or too poorly exposed to provide suffi cient detail for the database, the best known is the Golden Mile Dolerite — a differentiated (micro-)gabbroic sill (Clout et al., 1990) that is the main host to gold mineralization at Kalgoorlie–Boulder. Gabbro variants in the EGGGT include equigranular gabbro (A-oge), very coarse grained gabbro (A-ogd), leucogabbro (A-ogl), porphyritic gabbro (A-ogp), quartz-bearing gabbro (A-ogq), and pyroxenitic gabbro (A-ogx). Anorthosite (A-oa), olivine gabbronorite (A-ol), and olivine gabbro (A-oo) have been distinguished in some areas. Compositional and cumulus layering indicative of differentiation is evident in many intrusions. In some areas this provides the only indication of younging direction, as in the minor sill adjacent to the Hootanui Fault, where a hornblende–quartz granophyre (A-gv) top indicates younging toward the centre of the Duketon greenstone belt. Strongly foliated gabbro (A-mogs), epidotized gabbro (A-mogd), and amphibolite derived from gabbro (A-moa) have been recorded on some maps.

Dolerite or microgabbro (A-od) locally forms cross-cutting intrusions, but commonly forms concordant layers in basalt. It is unclear whether these rocks represent sills or coarser grained portions of thick lava fl ows, but both modes of origin are possible. In moderately deformed sequences basalt absorbs much of the strain so that doleritic layers contain only a weak foliation. The dolerite sills and dykes are narrow, fi ne grained, and lack clearly differentiated units. Petrographically, these rocks typically consist of fi ne-grained plagioclase and amphibole (actinolite and/or hornblende), with chlorite and epidote as common subordinate minerals. Primary intersertal to subophitic and ophitic textures are replicated by the metamorphic minerals. Dolerite can be equigranular (A-ode) or feldspar-phyric (A-odp) with plagioclase phenocrysts in a typically subophitic groundmass.

Norite and gabbronorite (A-ow), which outcrop on MELITA, BURTVILLE, and KANOWNA, typically have mesocumulate to orthocumulate textures. Plagioclase is commonly tabular to lath-shaped with weak to moderate compositional zoning. Hypersthene is predominantly a cumulus phase (but less commonly an intercumulus mineral), and augite, also a cumulus phase in some samples, is more commonly oikocrystic.

Mafi c intrusive rocks — named

The Kilkenny Gabbro (A-_kk-og) is a layered gabbroic sill with a thickness of about 600 m. It is underlain by spinifex-textured basalt and overlain by metasedimentary rocks. The sill has a pronounced igneous layering,

with a lower olivine–plagioclase zone and an upper augite–plagioclase cumulate zone. Discontinuous, thin rhythmic layering is common in the lower zone, which has a thickness of about 150 m. The upper zone consists of three conformable layers (leucogabbro, gabbro, and ferrogabbro) in an upward sequence. Cryptic variation in the composition of plagioclase and augite suggests fractional crystallization from a single magma pulse by gravity settling (Hallberg, 1985).

Layered mafi c to ultramafi c intrusions — named

Layered mafi c to ultramafi c intrusions form a small (2%) but signifi cant proportion of the EGGGT's greenstone belts. Rock types vary from peridotite and pyroxenite to gabbro, quartz gabbro, and anorthosite, with compositional layering and cumulate textures indicating differentiation in most intrusions. The geology of the layered intrusions of the EGGGT has been described by Williams and Hallberg (1973), Witt et al. (1991), and in the explanatory notes of the maps where the intrusions are best exposed. These units have conformable or semi-conformable relationships with their host sequences and have been referred to as sills. Hill et al. (1990, 1995) recognized many of these bodies as infl ated lava fl ows. In this dataset, the major layered intrusions are identifi ed by the initial letters of the intrusion name, with suffi x letters for subunit lithology.

In the southern EGGGT the layered mafi c intrusions are best exposed and documented on BARDOC and DAVYHURST, where at least four are distributed around the major Goongarrie – Mount Pleasant anticlinal arch. The Mount Ellis Intrusion, the lowermost of these, outcrops in the hinge zone of the anticline. Witt et al. (1991) and Witt (1994b, 1995) identifi ed a basal olivine gabbro–gabbronorite with pyroxenite and pyroxene-phyric dolerite (A-ME-ax), followed by porphyritic leucogabbro (A-ME-ogl) and gabbro (A-ME-og) in which clino-pyroxene phenocrysts are variably abundant, and an upper granophyric quartz gabbro (A-ME-gu) that is capped by porphyritic dolerite.

Adjacent to and stratigraphically above the Mount Ellis Intrusion, the Mount Pleasant Intrusion is a layered mafi c–ultramafi c sill, about 550 m thick, that outcrops prominently over a strike length of more than 70 km around the Goongarrie – Mount Pleasant Anticline. According to Witt (1994b) and Witt et al. (1991), this sill contains a melanocratic microgabbro at the base that is successively overlain by an ultramafi c layer with zones of olivine orthocumulate (A-MP-ad) and pyroxenite(A-MP-ax), a gabbronorite layer (A-MP-om) that represents a marker horizon, a leucograbbro–gabbronorite (A-MP-ogl) and gabbro (A-MP-og) layer, an ilmenite-rich quartz ferrogabbro with pronounced granophyric quartz–albite intergrowths (A-_MP-gv), and another gabbro layer at the top.

Higher in the succession, the Ora Banda Intrusion is a large, layered mafi c and ultramafi c sill comprising, from the base up: peridotite (dunite; A-OB-ad); orthopyroxene (bronzitite) adcumulate (A-OB-ax); norite; gabbronorite

3


2

with small, irregular patches of anorthosite (A-OB-om); gabbro; and granophyre (A-OB-gu).

The Orinda Intrusion is the structurally uppermost sill in this area, adjacent to the Ora Banda Intrusion. Differentiation has produced compositional layering, with a lower unit of gabbronorite and gabbro (A-OR-og), and quartz gabbro and iron-rich granophyre (A-OR-gv) in the upper portion.

The Powder Intrusion is a sill that intruded the predominantly felsic volcanic and sedimentary sequence immediately west of the Zuleika shear, 20–35 km north of Coolgardie. The sill occupies a southeast-plunging synform, with the most differentiated and thickest part (possibly 1000 m) of the intrusion in the fold closure.A lower gabbro and gabbronorite unit (A-PW-og) underlies an upper portion of leucocratic quartz gabbro(A-PW-ogl) containing irregular patches of granophyre (Hunter, 1993).

The Three Mile Intrusion (A-TM-og) intrudes the basalt sequence north and northeast of Coolgardie. Wyche (1998) described a section with distinct igneous layering, from pyroxenite at the base, up through gabbro, to porphyritic leucogabbro (locally glomeroporphyritic) with coarse clinopyroxene phenocrysts, in turn overlain by gabbro, then quartz gabbro, capped by a thin unit of gabbro.

The Mount Thirsty (A-MT) and Mission (A-MI) Intrusions, west to northwest of Norseman, intrude the mafi c–ultramafi c sequence along a strike length of about 20 km, and amount to about 1500 m of the total greenstone sequence (making up a considerable proportion of the outcrop). These sills comprise lower cumulate-textured pyroxenite (A-MT-ax, A-MI-ax), locally underlain by serpentinitized peridotite (A-MT-ap, A-MI-ap), and overlain by upper units of norite and gabbro (A-MT-og,A-MI-og), and quartz gabbro with granophyric segregations (A-MT-gu).

The Mount Monger (A-MM-og) and Oak Hill(A-OH-og) Sills are dominated by gabbro with relict cumulate textures, whereas the Seabrook Intrusion displays a complete compositional gradation from a lower peridotite unit (A-SE-ap) through to a pyroxenite (A-SE-ax), and into gabbro (A-SE-og).

Dolerite and cumulate-textured gabbronorite and gabbroic anorthosite, mainly in the Niagara mining area on MELITA, were grouped as the ‘Niagara Layered Complex’ by Witt (1994b), who noted similarities to the Carr Boyd Rocks Complex farther south. This defi nition has not been used here because the distribution of sills and dykes attributed to the complex was not shown on MELITA, and the sills on YERILLA included in the complex are not distinctive in the fi eld. Witt (1994a) suggested that the presence of anorthositic and quartz–magnetite-enriched gabbros is evidence of an extensive layered intrusion, and recorded the sills as up to about 400 m in thickness. Ultramafi c cumulates are only locally recognizable in these sills.

The Kathleen Valley Intrusion is a large, composit-ionally layered sill on MOUNT KEITH and SIR SAMUEL.


Compositional layering trends indicate that it is over-turned and thus youngs to the southeast, despite the steep northwesterly dip of primary igneous layering. Fromthe stratigraphic base upward, the intrusion comprises seven distinct layers (Jagodzinski et al., 1999; Liu, 2000):• gabbro (A-KV-ogy), at least 1100 m thick, with

rhythmic layering defi ned by varying proportions of amphibole and plagioclase;

• anorthositic gabbro and anorthosite (A-KV-oa) layer, up to 1700 m thick, with plagioclase (labradorite) as both phenocryst and groundmass phases;

• medium-grained metagabbro (A-KV-og), about 1500 m thick;

• metamorphosed pyroxenitic gabbro (A-KV-ogx), about 100 m thick;

• quartz gabbro and tonalite layer (A-KV-gu), 500 m thick;

• quartz-bearing gabbro (A-KV-ogq) layer, 200 m thick; • coarse-grained metagabbro (A-KV-og), 100 m thick.

Several other intrusions have been named and described in the explanatory notes, but not examined in detail, and subdivisions have not been shown on the published maps.

Granitic rocks

Granitic rocks are the dominant rock type in the Yilgarn Craton and comprise about 48% of the outcrop in the database area. In outcrop, most granitic rocks in the EGGGT and SCGGT are strongly weathered, and are preserved either in breakaways where variably kaolinized and silicifi ed granite is exposed below eroded silcrete duricrust or as variably weathered remnants in areas of quartzofeldspathic sand. Less commonly, relatively fresh outcrops are exposed as isolated whalebacks, pavements, and tors. This section summarizes details of unassigned granitic rocks only.

Large areas of granitic outcrop are too weathered to allow classifi cation, apart from the recognition of common granitic characteristics (A-g). Where weathering is more intense, residual granitic regolith may be classifi ed as deeply leached granitic residuum (_R-g-pg) or silcrete with kaolinite after granite (_R-d-pg; see below).

Monzogranite (A-gm) is the most common granitic rock type of the EGGGT. It is typically leucocratic with less than 10 % modal mafi c minerals (mainly biotite), and varies from equigranular to porphyritic (A-gmp). Where grain size is consistent over an extended area, coarse- (A-gmd), medium- (A-gmm), and fi ne-grained (A-gma) varieties are distinguished. Hornblende–biotite (A-gmh) and quartz-rich (A-gmq) monzogranite are recorded in some areas. Syenogranite (A-gr) is less common than monzogranite but can be locally abundant; it constitutes most of the granitic rocks on WEEBO, where a fi ne-grained variant (A-gra) is also exposed.

Granodiorite (A-gg) and tonalite (A-gt) are widespread in the EGGGT, but are less abundant than monzogranite. Dominantly granodioritic intrusions are exposed on DARLOT, YEELIRRIE, LEONORA, LAKE CAREY, and EDJUDINA.


4
2
Porphyritic granodiorite (A-ggp) is identifi ed only onMILLROSE. A tonalite to biotite tonalite (A-gt) body intrudes greenstones southwest of Mount Grey on WANGGANNOO, and there are smaller intrusions on MOUNT KEITH, WILDARA, and EDJUDINA. Tonalite (A-gt) and porphyritic tonalite (A-gtp) in the core of the Lawlers Anticline have an intrusive contact with the Agnew–Wiluna greenstone belt and were interpreted by Platt et al. (1978) as a tabular body emplaced before the earliest deformation in the area.

Volumetrically minor diorite (A-gi) and porphyritic diorite (A-gip) intrusions form small clusters on WEEBO, MILLROSE, and YABBOO. Quartz diorite to quartz monzodiorite (A-gd) was mapped on MOUNT BELCHES. Numerous minor intrusions, typically plutons or dykes of porphyritic monzodiorite (A-ghp), outcrop sporadically throughout the area.

Alkaline intrusions are scattered throughout the EGGGT. The largest vary in composition from quartz monzonite (A-gc) to monzonite (A-gz) and quartz monzodiorite (A-gkp). These intrusions, exposed in the northern part of MILLROSE but visible only in the subsurface west of Lake Ward, correspond to prominent highs on magnetic images (Farrell and Wyche, 1999). Small plutons and dykes of syenite (A-gy) are widespread in the EGGGT. These are typically post-tectonic and show no evidence of deformation, except for the largest syenite intrusion (A-mgws) at Mount McKenna, east of Laverton, which has a penetrative foliation inclined moderately to the east-northeast. Syenite to quartz syenite with numerous mafic schlieren and xenoliths (A-gyi) forms several moderate-sized bodies on WANGGANNOO. Quartz syenite (A-ge) outcrops on ROE, and quartz syenite with numerous mafi c enclaves (A-gei) has been mapped on PINJIN. Alkali-feldspar granite (A-gf ) outcrops on LAKE CAREY.

Granophyre (A-gv) is typically associated with the uppermost, most differentiated parts of mafi c layered intrusions and gabbroic sills.

On several of the 1:100 000 map sheets covering the northern part of the EGGGT, identifi cation of granites was largely based on grain size rather than compositional criteria. Although most of these granites are likely to plot in the monzogranitic modal fi eld, a generalized code has been retained for these occurrences. Fine-grained (A-gna), medium-grained equigranular (A-gnme), and coarse-grained (A-gnd) varieties are distinguished. Undifferentiated leucocratic (A-gnl) and quartz-rich (A-gnq) granitic rocks have been coded separately.

Porphyritic felsic units (A-gnp), considered to be mainly intrusive, typically form dykes or sills in the greenstone belts, generally from 1 to 5 m in width or thickness, and rarely exceeding 10 m. They are variably deformed and commonly strongly foliated along contacts. An intrusive origin is evident locally where dykes appear to post-date at least some of the earliest deformation, or are discordant relative to known stratigraphy. These porphyritic units may represent high-level intrusions associated with nearby granitic rocks. Those units that are discordant to early structural features, but have undergone all subsequent deformation, can be useful chronological markers. Quartz–feldspar(–biotite) porphyritic rock

(A-gnpq) is the most abundant type and typically contains 5 to 10% phenocrysts (commonly less than 2 mm but up to 5 mm across) of quartz and feldspar (dominantly plagioclase), with up to 5% biotite in a microcrystalline groundmass. Hornblende-bearing, plagioclase-phyric porphyritic veins (A-gnph) are locally abundant.

Granitic rocks have been variably affected by deformation and metamorphism, particularly along faults and shear zones at granite–greenstone contacts. Foliated granitic rock (A-mgss) is commonly preserved as weathered exposures, generally as thin slices within greenstones. Gneissic granitic rock (A-mgsn) consists of strongly to moderately foliated granite with a local gneissic component that is commonly transitional between foliated monzogranite (A-mgms) and granitic gneiss (A-mgn). Distinction between gneissic granite (A-mgsn) and strongly foliated granite (e.g. A-mgss, A-mgms) is somewhat subjective and, apart from map sheet boundary discrepancies, there has been no attempt to standardize usage of these terms throughout the database area. Rather, the terminology used in the published map sheets has been retained. Granitic gneiss (A-mgn) ranges from monzogranite to tonalite. Banding is typically the result of varying biotite concentration, although thin aplitic and pegmatitic veins may be common. Local deformation of the banding into upright tight folds indicates a pre-D2 origin. Rotated feldspar porphyroclasts and mineral elongation lineations are also common features of granitic gneiss. Attenuated enclaves of metamorphosed mafi c rock are locally common. Variants include quartz-rich granitic gneiss (A-xmg-mnf ), augen-textured granodiorite and tonalite gneiss (A-mggu), and K-feldspar–quartz gneiss (A-mgrn). Leucocratic gneissic granitic rock (A-mgln) has been distinguished on BALLIMORE. Granite hornfelsed (A-mge) by the Binneringie Dyke is exposed on COWAN.

Shear zones at the granite–greenstone contact may be complex zones containing metre-scale interlayering of various rock types. The mixed rock codes used to characterize these exposures commonly only indicate the dominant rock types. The most common associations are foliated granite interleaved with subordinate amphibolite and foliated mafi c rock (A-xmgss-mba), and quartzofeldspathic gneiss interleaved with amphibolite and metamorphosed mafi c rock (A-xmgn-mba). Granodiorite and monzogranite interleaved with diverse greenstone rock types (A-xmgg-mb) and granitic to granodioritic porphyritic dykes and sills interleaved with metasedimentary quartz–chlorite schist (A-xmg-ms) have been distinguished on MELITA and MOUNT BELCHES respectively. Some of these lithologically heterogeneous units are clearly visible on magnetic images, for instance along both the eastern and western margins of the granite separating the Agnew–Wiluna and Yandal greenstone belts, and west of the southern part of the Agnew–Wiluna greenstone belt.

Granitic rocks and granitic suites — named

A large number (53) of granitic intrusions have been named in the area covered by the EYGD (Appendix 1).

5


2

These intrusions are distinguished on the basis of their characteristic spatial distribution and relationships, and are commonly clearly identifi able on magnetic images. They are largely monzogranitic and granodioritic in composition, but syenogranite, tonalite, quartz monzonite, and syenite intrusions have also been identifi ed. For detailed descriptions of these intrusions, the reader is referred to the relevant sets of explanatory notes accompanying the 1:100 000-scale maps (Table 1).

Only one granitic suite has been recognized in the database area. The Erayinia Granitic Suite (A-ER-g) on ERAYINIA and ROE ranges in composition from monzo-granite to quartz syenite and syenite, typically with hornblende or clinopyroxene, and locally abundant mafi c xenoliths.

Only one unit of granitic gneiss has been named in the EGGGT. The Fifty Mile Tank gneiss (A-_ fi-mgn) is a major feature of the Pioneer Dome in the southern part of the Kalgoorlie terrane, covering an area 18 km long and up to 2.5 km wide east of the Pioneer Monzogranite. Gneissic banding comprises millimetre-scale variations in biotite content, with zones in which macroscopic banding is defi ned by variation in the abundance of pegmatite in broad (100 to 300 m-wide) bands (A-_ fi-mgnp).

Mafi c meta-igneous rocks

Metamorphosed mafi c rocks on KANOWNA are too altered for a protolith to be identifi ed, although a possible derivation from basalt, dolerite or gabbro was inferred (A-mw). Amphibolite with relict plagioclase phenocrysts (A-mwa) was identifi ed on MELITA.

Felsic meta-igneous rocks

Banded to agmatitic felsic gneiss (Amrn) outcrops mainly in the northern part of the EGGGT. In the Kalgoorlie terrane, albite-rich, quartz-poor porphyritic dykes (Amzrf ) are considered the product of sodium metasomatism of spatially associated hornblende–plagioclase porphyritic rock (Witt, 1992).

Metasomatic rocks

Two types of metasomatic rocks have been identifi ed in the area covered by the database. Massive carbonate rock (Amzk), locally recrystallized or schistose, outcrops on ROE and YABBOO. Greisen veins (Amzr) are recorded on BALLARD.

Metamorphic rock — protolith unknown

Although all Archaean rock types in the EGGGT have undergone at least low-grade metamorphism, protoliths are commonly recognized and the terminology used in the database is based on primary composition. However, there are several instances where protolith identity is obscure, due to intense deformation combined with recrystallization. Such rocks are classifi ed using


metamorphic terminology, and a primary rock type may only be inferred from composition and lithological associations. Metamorphic rocks with unknown or uncertain protolith are coded into three main groups: schist (A-ms), gneiss (A-mn), and granofels (A-me), with additional codes characterizing further structural features, metamorphic mineralogy, and mixed rock types.

Of the low- to medium-grade metamorphic rocks, the more common rock types are:• amphibolite (A-msa; locally with biotite, A-msab);• quartzofeldspathic schists (A-msqf), locally with

dominant biotite (A-msqb), chlorite (A-msqc), or muscovite (A-msqm);

• melanocratic schists with biotite (A-msb), chlorite (A-msc) or actinolite and chlorite (A-msrc).

Muscovite–quartz schist (A-msmq) can be interlayered with fuchsite–quartz(–andalusite) rock (A-msmu). Aluminous rocks include quartz-rich schists characterized by andalusite porphyroblasts (A-msd) or kyanite (A-msqk), locally with chloritoid and biotite, and kyanite-bearing felsic schists (A-msk). Schists containing aluminous silicates are probably pelitic in character, but whether they are derived from truly argillaceous, immature sedimentary precursors, or felsic volcanic and volcaniclastic rocks is unclear, particularly where these rocks are closely associated with fragmental volcanic rocks (e.g. on EDJUDINA). It is possible that very early weathering or hydrothermal alteration led to kaolinitic profi les near some of the vents, thereby producing aluminous protoliths with no sedimentary history. Ferruginous rock types include schists (A-msj) and grunerite–hornblende–magnetite–plagioclase rock (A-msjg). Phyllonite and mylonite (A-mspy) are typically exposed in fault and sheared zones. The Bardoc Tectonic Zone (Witt, 1994a; Swager et al., 1995) on the boundary between the Boorara, Ora Banda, and Kambalda domains (Fig. 3) is characterized by a melange of schists representing originally mafi c, ultramafi c, and felsic rocks that exhibit strong carbonate alteration (A-mvks). Shear zones are also characterizedby interleaving of diverse rock types, such as schistderived from mafi c and ultramafi c protoliths (A-xmsw-msu), or amphibolite and quartzofeldspathic rocks(A-xmsa-mfs).

Gneissic rocks are restricted to areas where metamorphic grades attained upper amphibolite facies. Amphibolitic gneiss (A-mna) was mapped on GINDALBIE, where it occupies about 50 km2 in the northeastern corner of the map and is completely surrounded by granite. Melanocratic gneiss with minor melanocratic schist (A-mnw) has been separated on GINDALBIE and MELITA, whereas calc-silicate gneiss (A-mnkq) has been recognized in the subsurface on MILLROSE.

Isolated exposures of granofelsic rocks (A-me) in the EGGGT are largely coded according to the characteristic metamorphic mineral phase, and include quartzitic(A-meq), quartz–chloritoid–andalusite (A-mehd), quartz–chloritoid–kyanite (A-mehk), and quartz–fuchsite(A-memu) varieties. High-grade pyroxene hornfels (A-mex) is exposed on LAKE VIOLET and adjacent to noritic rocks on northwestern BURTVILLE.


Dykes and veins,unassigned age

Numerous dykes and veins crosscut the lithologies of the EGGGT and central-eastern SCGGT. The most common varieties are quartz veins and pods (zq), microgranite (gna), granite (g), and pegmatite (gp). Granodiorite (gg), diorite (gi), granophyre (gv), tonalite (gt), and epidosite (zd) are subordinate, as are quartz veins with goethite (zqi) and brecciated textures (zqix). Mafi c dykes are mainly doleritic (od). Lamprophyre dykes (y) are clustered on southern MINERIE, but are rare elsewhere. Ages for these rocks are uncertain, but fi eld relations commonly suggest an Archaean age.

Proterozoic geology

Mafi c and ultramafi c dykesUndeformed Proterozoic dykes (P_-od), mainly of fi ne- to medium-grained gabbro, but ranging in composition from pyroxenite through gabbronorite to granophyre, intrude the Archaean granites and greenstones and have easterly to northeasterly and north-northwesterly trends. Although locally exposed as ridges, most of the dykes are covered by surfi cial deposits. A distinctive regolith unit comprising red-brown soils demarcates the extent of some of these dykes (_R-m-p), but recognition of their widespread distribution, abundance, and extent has depended upon the availability of regional aeromagnetic surveys.

The east-trending dykes were grouped into the Widgiemooltha Dyke Suite (see below) by Sofoulis (1966) and described in some detail by Hallberg (1987). An early Proterozoic age was confi rmed for an easterly trending dyke by Nemchin and Pidgeon (1998). Northeasterly trending dykes with similar characteristics may be attributed to the 1220 Ma Mesoproterozoic Fraser Dyke Swarm in the southern part of the EGGGT (Wingate et al., 2000).

Gabbro sills are associated with basaltic lava fl ows in the Yerrida Group (see below), and dykes of the same age (c. 2200 Ma) are likely. In areas covered by the Yerrida Group on CUNYU, northeast-trending magnetic anomalies are better defi ned than those trending westerly or northwesterly, and hence may represent dykes extending to shallower levels, with dykes in other orientations partly obscured by the Palaeoproterozoic cover.

Mafi c and ultramafi c dykes — namedThe Widgiemooltha Dyke Suite (Sofoulis, 1966; Hallberg, 1987) includes a number of dykes that have been individually named. The Binneringie Dyke (P_-Wb-o), the largest of these intrusions, can be traced for 600 km across almost the entire Yilgarn Craton, from the Albany–Fraser Orogen in the southeast to the Boddington area in the northwest. It is best exposed along the northern

26

shore of Lake Cowan as a chain of hills, and attains a maximum width of 3 km. Despite its size, only vertical layering has been recognized in this intrusion, unlike the Jimberlana Dyke (see below). A precise baddeleyite U–Pb date of 2418 ± 3 Ma was determined for this dyke using a sample collected near its western extremity (Nemchin and Pidgeon, 1998).

The Jimberlana Dyke outcrops on NORSEMAN.Magnetic, gravity, and diamond drillcore data reveal a structure in which compositional layering defi nes listric conical intrusions at several points along the dyke’s 180 km length. These canoe-shaped complexes have a well-developed rhythmic differentiation pattern similar to the Great Dyke in Zimbabwe, as described by Campbell (1968, 1978), and McClay and Campbell (1976). Norite (P_-Wj-ow) and pyroxenite (P_-Wj-ax) are the main rock types.

Several other dykes have been named in the southern part of the EGGGT. These are the Celebration (P_-Wc-o), Randalls (P_-Wr-o), Pinjin (P_-Wi-o), Kalpini (P_-Wk-o), and Ballona (P_-Wl-o) Dykes. All trend about 075° and, together with the Binneringie and Jimberlana Dykes, have positive magnetic anomalies. In contrast, three prominent negative magnetic anomalies trending about 085° represent unexposed dykes between the Randalls and Binneringie Dykes. Less substantial magnetic anomalies parallel to these trends suggest that there are many more minor dykes in this swarm. Their differing palaeomagnetic characteristics may refl ect different periods of magmatism (Williams, 1970).

Felsic dykesProterozoic felsic dykes are rare in the EGGGT, and are largely of dioritic composition (P_-gi).

Yerrida and Earaheedy BasinsPalaeoproterozoic volcanic and sedimentary rocks in the far northeastern and northwestern parts of the database area were deposited in the Yerrida and Earaheedy Basins (Fig. 3).

Yerrida Basin

The 2200 Ma Yerrida Group (Woodhead and Hergt, 1997) is exposed on CUNYU and WILUNA, in the northwestern part of the database area. This group is a redefi ned subdivision of a sequence previously ascribed to the Glengarry Basin (Gee and Grey, 1993; Pirajno et al., 1996, 1998). Minor deformation of the Yerrida Group is characterized by gentle dips and local open, northwesterly plunging folds (Adamides et al., 1999).

Windplain Subgroup — Juderina Formation

The basal Juderina Formation (P_-YWj-s), of the lower Windplain Subgroup, contains a sedimentary sequence dominated by mature siliciclastic arenite, cross-stratifi ed conglomerates, and intercalated siltstone deposits of the

a
GSWA Report 95 East Yilg
2

Finlayson Member (P_-YWjf-sa), with less common silicifi ed evaporites and laminated stromatolitic chert and carbonate beds of the Bubble Well Member (P_-YWjb-c). Unassigned shale and siltstone have also been mapped(P_-YWj-sl). This sequence has been attributed to deposition in an extensional rift environment (Pirajno et al., 1996).

Mooloogool Subgroup — Killara Formation

The Mooloogool Subgroup unconformably overlies the Windplain Subgroup and is represented only by the Killara Formation in the database area. This contains a sequence of aphyric basaltic lavas (P_-YMk-bb) and microgabbro sills (P_-YMk-od), intercalated with thin silicified volcaniclastic rocks and minor nontronite layers. The Bartle Member (P_-YMkb-cc) consists of variably laminated or brecciated chert and chertifi ed sedimentary rocks with evaporite affi nities. These rocks were interpreted as continental fl ood basalts and interfl ow sedimentary units (Pirajno et al., 1996, 1998).

Earaheedy BasinThe Earaheedy Group outcrops in the northeastern parts of BALLIMORE and DE LA POER (Figs 2 and 3), and consists of clastic and chemical sedimentary rocks deposited in coastal to shallow-marine environments of the Palaeoproterozoic Earaheedy Basin (Hocking et al., 2000). The sedimentary bedding dips at very shallow angles to the northeast (<5° on BALLIMORE, 0–15° on DE LA POER) because the rocks in this area lie on the southwestern limb of a regional-scale open syncline that plunges southeasterly at a shallow angle. Metamorphism is of very low grade.

The age of these rocks is not well constrained.A maximum age of 1850 Ma is provided for the Chiall Formation by detrital zircons (U–Pb SHRIMP; Halilovic et al., 2004). The basin was deformed during an orogenic event that Jones et al. (2000a) and Pirajno et al. (2004) tentatively correlated with the 1790–1760 Ma second stage of the Yapungku Orogeny (Bagas and Smithies, 1998).

The formalized stratigraphic subdivision of the Earaheedy Group by Hall et al. (1977) identifi ed the Tooloo (lower) and Miningarra (upper) Subgroups. The inferred disconformity between the subgroups has been interpreted either as rapid transgression after a lengthy period of minimal deposition, with localized intraformational conglomerates representing disrupted submarine hardground (Jones et al., 2000b), or as seismites due to far-fi eld earthquake activity (Pirajno et al., 2004). The assemblage of commonly fi ne grained clastic, ferruginous, and carbonate sedimentary deposits making up the Earaheedy Group has been interpreted as the result of sedimentation on a passive margin along the edge of the Yilgarn Craton, possibly with proximal mid-ocean ridge or oceanic plateau volcanism to account for the high iron content of the Frere Formation (Jones et al., 2000b; Pirajno et al., 2004).

The basal part of the Tooloo Subgroup consists of the Yelma Formation (P_-EAy-s), which comprises


7

pebbly sandstone (P_-EAy-st), arkose, shale, siltstone, conglomerate, stromatolitic dolomite (P_-EAy-k), and minor chert breccia. Sedimentary structures and facies relations indicate a coastal setting with both fl uvial and shallow-marine components. These rocks are overlain conformably by the Frere Formation (P_-EAf-ci), which has up to three units of granular iron-formation(P_-EAf-cig), consisting of jasperoidal, peloidal iron-oxide beds, separated by variably ferruginous shale, siltstone, sandstone, jasper, and chert beds (P_-EAf-sl). Although stromatolitic carbonate, siltstone, and shale from two small exposures on BALLIMORE have been interpreted to conformably overlie the Frere Formation (Whitaker et al., 2000), Jones et al. (2000a) suggested that these rocks correlate with the upper Frere Formation in adjacent areas, and have assigned them to the Windidda Member (P_-EAfd-kl).

The uppermost Miningarra Subgroup is represented in the map area only by the Chiall Formation,and consists of shale and siltstone of the Karri Karri Member(P_-EAck-sl), and the overlying sandstone and shale of the Wandiwarra Member (P_-EAcw-ss).

Proterozoic sedimentary rocks of fl uvial originInferred Proterozoic outliers of fl uvial origin (P_-s) overlie the Yilgarn Craton at several localities. The largest exposure is that of the fl at-lying Kaluweerie Conglomerate on DEPOT SPRINGS (Allchurch and Bunting, 1976). The lowermost unit, a polymictic conglomerate (P_-_k-scp), contains clasts of local provenance (including granite, gneiss, basalt, and BIF) and a matrix with little or no clay or silt. The overlying lithic sandstone unit (P_-_k-ssa) varies from fi ne to coarse grained, and locally contains similar clasts to the conglomerate.

Permian geologyOutliers of Permian glacial deposits unconformably overlying the Archaean Yilgarn Craton are mostly assigned to the Paterson Formation of the Gunbarrel Basin. Conglomerate (P-_a-sgpg) contains granite and greenstone clasts, commonly with striations, in a clay- and silt-rich matrix. Shale and siltstone units (P-_a-sl) are fl at lying and locally contain dropstones. Sandstone to pebbly sandstone units (P-_a-ss) probably represent fl uvial deposits. Unassigned conglomerate (P-sc) and shale and siltstone (P-sl) on SIR SAMUEL, DARLOT, and DUKETON have been correlated with the Paterson Formation (e.g. Westaway and Wyche, 1998). Thin layers of undeformed, unmetamorphosed, matrix-supported conglomerate and coarse-grained, poorly sorted sandstone, locally capped by silcrete, are preserved as small mesas on EDJUDINA.The presence of striated, angular quartz pebbles supports the interpretation that these are glacigene deposits, equivalent to the Permian Wilkinson Range Beds that overlie the Offi cer Basin to the east (Williams et al., 1976).


2

Cainozoic geology

Eucla Basin, Eundynie GroupUpper Eocene Eundynie Group sedimentary rocks (Ee-E-s; Cockbain, 1968a,b) are exposed in the southern part of the database area, within the Cowan and Lefroy palaeodrainage channels. These rocks indicate deposition in shallow-water settings and comprise fl uviodeltaic channelled and cross-bedded sandstone, siltstone, and conglomerate of the Pallinup Formation (Ee-Ep-st), increasingly interspersed with spongolite and macrofossiliferous limestone to the south (Ee-E-kl; Clarke, 1994).

Regolith geologyRegolith deposits constitute about 90% of the area covered by the database (Fig. 2). They comprise either unconsolidated or weakly cemented sediments, or saprolite and other derivatives of in situ weathering. A complete reinterpretation of the regolith geology for the 1:100 000-scale geological maps of the EGGGT was carried out to create a ‘seamless’ regolith coverage as part of the EYGD (Riganti et al., 2003). Regolith reinterpretation was undertaken using Landsat TM images (bands 7, 4, 1, and Gozzard ratio 5/7, 4/7, 4/2) and recently published 1:100 000-scale geological maps, together with limited fi eld checking.

Regolith units are coded according to the GSWA regolith classifi cation scheme of Hocking et al. (2001), which is based on the Residual–Erosional–Depositional (RED) scheme of Anand et al. (1993). In addition to the erosional regime (X) typical of bedrock exposures, the main regolith elements are colluvial (C), alluvial (A), sheetwash (W), and lake deposits (L), which represent increasingly distal transport and deposition. Relict or residual deposits (R) represent either remnants of a previous land surface or in situ weathering products of the underlying bedrock. Eolian and residual sandplain deposits (S) developed in various parts of the landform profi le. The regolith types recognized are listed in Appendix 1. Note that codes are provided in database format and lack typescript settings (e.g. italics and subscript) used in published GSWA maps.

Overviews of the regolith geology of the Yilgarn Craton by Anand and Paine (2002) and Hocking and Cockbain (1990) provide a framework for the interpretation of the surfi cial cover. More detailed reports from the Cooperative Research Centre for Landscape Evolution and Mineral Exploration (CRC LEME) projects (such as a study of the Yandal greenstone belt; Anand, 2000) recognized that weathering and drainage systems have evolved over the last 60 million years. The Yandal greenstone belt study (Anand, 2000) revealed that weathering is common to depths of 150 m, and 90% of the area is covered by transported regolith that is 3 to 40 m thick, with palaeodrainage channels to depths of 100 m (Anand, 2000). Several references in Phillips and Anand (2000) address geochemical dispersion in regolith around mineral deposits in the northern part of the EGGGT.

8

Residual or relict units‘Residual’ regolith units are those where regolith is the product of in situ weathering, whereas ‘relict’ is used for landforms where regolith is of uncertain origin, either transported or residual. Only one exposed unit has been identifi ed (_Xw), and it has been included with these units for simplicity. Undivided residual or relict material (_R-d) comprises dominantly ferruginous and siliceous duricrust, which commonly grades laterally over short distances into either calcrete or kaolinized rock. This duricrust is particularly well developed over granitic rock, and is commonly covered by a variably thick layer of largely residual yellow quartzofeldspathic sand with minor pisolitic laterite, ferruginized silcrete, silt, and clay (_S-l).

Ferruginous duricrust (_R-f), previously termed ‘laterite’ on several published 1:100 000-scale maps, consists of nodular, pisolitic or massive ferricrete. It is yellowish to dark-brown and locally black, and is developed over both greenstones and granitic rocks, particularly in the southern EGGGT. Jutson (1934) originally interpreted ferruginous duricrust as isolated, eroded remnants of an old, extensive, lateritized peneplain. However, these deposits are distributed at a wide range of altitudes (Davy and Gozzard, 1995), either as residual or reworked transported material formed at different times in the last 50 million years. Ferruginous duricrust typically outcrops in breakaways overlying highly weathered (bleached and mottled) rocks, in weathering profi les up to 100 m thick. Where the preservation of textures indicates that ferruginous duricrust has formed directly from the underlying bedrock, composite codes have been used (e.g. _R-f/A-b, where ferruginous duricrust is derived from the in situ weathering of metamorphosed mafi c volcanic rock). Massive ironstone (_R-f-i) forms ridges and cappings on greenstones (mainly ferruginous sedimentary and mafi c rocks) on SIR SAMUEL, and in the central and northern parts of the EGGGT. On several maps used to construct the database, ‘laterite’ was also used for areas of relict material that included ferricrete, reworked ferricrete (e.g. scree slopes), ‘hardpan’, and gravelly or pisolitic soils, together with nodular carbonate ‘kankar’ or calcrete. These areas have been classifi ed as residual or relict material (_R-d) in this interpretation, or are suitably subdivided.

Residual quartzofeldspathic sand (_R-g) typically derived from granite, granitic gneiss, and felsic volcanic rocks comprises quartzofeldspathic sand, scattered deeply weathered outcrops, and locally abundant pebbles of vein quartz and silcrete. In areas unequivocally underlain by granite bedrock, residual quartzofeldspathic sand (_R-g-pg) contains small granite outcrops, and includes mottled and leached zones of weathering profi les in the gently sloping areas at the foot of breakaways. Adjacent to granitic outcrops, residual quartzofeldspathic sand is commonly overlain by colluvium. In many cases a complete gradation exists between granite outcrop, residual quartzofeldspathic sand, and sandy sheetwash.

Massive to nodular calcrete (_R-k) is preserved in small isolated areas, predominantly in the southern EGGGT. It is typically developed over ultramafi c rocks on DAVYHURST.


29

Most of the calcrete occurrences on the original geological maps used to compile the EYGD, particularly in the central and northern EGGGT, have now been reinterpreted as groundwater calcrete according to the classifi cations of Mann and Horwitz (1979) and Anand and Paine (2002). Magnesite-rich units derived from ultramafic rocks(_R-km-u) are exposed at several localities, but are only well developed on KANOWNA.

Residual, commonly dark red, unconsolidated soil is developed over Proterozoic mafi c and ultramafi c dykes (_R-m-p) on NORSEMAN, KURNALPI, and ROE.

Silcrete (_R-z) is commonly developed over granitic or other quartzofeldspathic rocks. It varies from a thin (0.5 m) locally developed layer in the southern EGGGT to a widely distributed, and locally abundant unit in the central and northern parts. It is commonly light grey to white, and is represented by either massive chalcedony or, more commonly, by angular, millimetre-sized quartz clasts set in cryptocrystalline (subvitreous to vitreous) siliceous cement (Butt, 1985). Where silcrete is derived from granite (_R-d-pg), the outcrop style mimics that of fresh granite. In these occurrences, silcrete either directly overlies granite or is separated from it by a kaolinite-rich unit up to 2 m thick. Weathering of silcrete in these areas, particularly in the north, has resulted in extensive fi elds of silcrete boulders, typically 30–50 cm in diameter, resting on kaolinized granitic rock. Silcrete in which the siliceous cement is impregnated by iron oxides and hydroxides(_R-z-i) commonly marks the transition between siliceous and ferruginous duricrust, as developed on WEEBO.Siliceous caprock (_R-z-u) is pale to dark brown or off-white and subvitreous. It is typically developed over ultramafi c rocks, particularly over serpentinized peridotite, where olivine-cumulate textures are very well preserved. Chrysoprase and jasperoidal chalcedony units are typically less than a metre thick, but up to several metres thick locally.

Intense weathering has resulted in the development of saprolite in several areas. These units have been coded _Xw.

Depositional units

Alluvial deposits

Alluvium (_A) occupies present-day drainage channels and fl oodplains, and consists of unconsolidated, poorly sorted sediments ranging from clay through to boulders, although most material is sand to gravel. Semiconsolidated, locally silicifi ed, poorly sorted gravel, sand, silt, and clay deposits restricted to old valley systems (_A2) are distinguished on WILDARA, MOUNT KEITH, DUKETON, and SIR SAMUEL. Semiconsolidated, ferruginous quartz sandstone deposits (_Av-q-s) characterize alluvial fans on the western shores of Lake Lefroy. At lower gradients, braided drainage lacks incised channels (_Ad), and comprises unconsolidated clay, silt, and sand. These systems form broad, locally swampy, swales up to several kilometres wide. Floodplains (_Af ), surrounding areas of channelized fl ows and braided drainage, are dominated by clay and silt deposits, with


local sandy tracts. All drainage in the Eastern Goldfi elds is ephemeral, but water can persist for longer periods in claypans (_Ap) along the major drainage lines and in fl oodplains.

Many alluvial deposits contain calcrete and carbonate cemented alluvium (_A-k). This groundwater calcrete (Mann and Horwitz, 1979; Anand and Paine, 2002) is typically located along major drainage paths, particularly in the lower reaches of stream systems. These calcareous valley-fi ll deposits, which form plains up to several kilometres wide, are characterized by scattered platforms with mantles of calcrete rubble and outcrop that can be partly obscured by alluvium. Individual calcrete deposits are commonly 5–10 m thick, but locally exceed 30 m in thickness (Anand and Paine, 2002). The formation of groundwater calcrete is attributed to in situ replacement of valley-fi ll debris, due to magnesium- and calcium-carbonate precipitation at or below the watertable from percolating carbonate-saturated groundwater (Mann and Horwitz, 1979). This process occurred during the Pliocene under arid climatic conditions characterized by low, irregular rainfall, high evaporation, little surface drainage or runoff, and a shallow watertable with sluggish groundwater movement (Hocking and Cockbain, 1990). Several groundwater calcrete deposits contain anomalous uranium concentrations as carnotite (e.g. the Yeelirrie orebody in the northern EGGGT; Keats, 1990).

Sheetwash depositsSheetwash (_W) is common on broad, gently sloping plains, gradational between colluvium and alluvium deposits. It consists of generally well sorted, reddish clay, silt, and fi ne-grained sand in extensive fans. The fi ne grain size and dominance of clay indicate that this material has been transported and substantially reworked from its source area. Fan-shaped clay-rich sheetwash deposits (_W-c) have been differentiated on DAVYHURST, BARDOC, and MOUNT MASON where they surround large claypans. Adjacent to ferruginous colluvial units, sheetwash deposits are characterized by abundant ferruginous grit (_W-f ). Sheetwash derived from low-lying granitic outcrops(_W-g) contains a higher proportion of quartzofeldspathic sandy material. Sheetwash with abundant quartz-vein debris (_W-q) is recognized on MOUNT MASON.

Colluvial depositsColluvium (_C) is common on slopes adjacent to rock outcrops. It includes poorly sorted rock fragments, gravel, sand, and silt from different rock types. The fi ne-grained matrix is locally ferruginous. Composite codes indicate areas where colluvium rests directly on bedrock (e.g. colluvium over basalt is coded as _C/A-bb). Colluvium has been further subdivided where a dominant lithotype can be identifi ed.

Iron-rich colluvium (_C-f ) is derived from reworked ferruginous duricrust and weathered ferruginized rocks, whereas colluvium composed of coarse-grained, angular debris of BIF and chert (_C-l-ci) is exposed on the fl anks of prominent BIF ridges. The weathering and erosion


30

of granitic rock (_C-g) produces quartzofeldspathic colluvium, commonly proximal to source, containing fragments of granitic rock, subordinate silcrete, and vein-quartz clasts. Partially reworked colluvium of this type grades laterally into sandy sheetwash and sandplain. Colluvium composed predominantly of angular quartz clasts (_C-q) is adjacent to prominent quartz veins, whereas colluvial material derived from siliceous caprock over ultramafi c rocks (_C-z-u) typically contains angular siliceous clasts.

Lacustrine deposits

The most common lacustrine deposits of the Eastern Goldfi elds are salt lakes (playas). They are associated with dunes and represent the remnants of largely southeasterly fl owing palaeodrainage systems (van de Graaff et al., 1977; Hocking and Cockbain, 1990). Unvegetated playa lakes (_Lp) are the dominant type, consisting of interbedded saline mud and clay covered by a veneer of halite and gypsum. Halophyte fl ats (dominated by samphire) with silt, sand, and gravel (_Lg) are locally developed adjacent to playa lakes.

Dune systems are within, and on the fringes of, the playas. Dune deposits (_Ld) consist of sand, silt, and gypsum derived from lakes and sandplains, with locally prominent mounds and dunes of lithifi ed gypsum and clay (_Ld-eg) such as on WANGGANNOO and YEELIRRIE. Different generations of dune deposits have been distinguished on some maps. Barren to poorly vegetated, active dunes (_Ld1) have minimal topographic expression, and form hummocky plains within and on the margins of lakes. Older, stabilized dunes (_Ld2) rise a few metres above the lake surface, have linear to gently undulating crests that can be several kilometres long and hundreds of metres wide, and range from gypsiferous sediments to red-brown sand and silt.

The fl at to gently undulating margins of playa lakes comprise a mixture of saline alluvial deposits and small channels, as well as small lakes, swamps, and claypans. These are associated with sandplain deposits in the form of sandy banks and lunettes (_Lm). Locally, scattered plains are mantled by calcrete rubble. Clay- and silt-dominated, typically circular depressions (_L-c), which are common in the lower reaches of the drainage systems (close to playa lakes), are characterized by ephemeral brackish or fresh water. Freshwater lakes within alluvial systems (_Lf ) are rare but locally prominent, such as Rowles Lagoon on DAVYHURST, and are commonly surrounded by swamps (_Lw).

Sandplain deposits

Sandplain deposits of variable thickness cover extensive areas adjacent to playa lake margins and on duricrust plateaus overlying granitic rocks. Extensive, fl at to gently undulating sandplains (_S) contain well-sorted, red, quartz-rich and clay-rich sand, representing a mixture of eolian and residual material, both locally sourced from quartzofeldspathic bedrock. Sandplains with well-developed dunes (_Sd) are commonly associated with

these deposits, with individual dunes extending for several kilometres. Sand dunes are also commonly developed on the eastern side of claypans (_Ap) as on YILMIA.

The transition between sandplain and playa terrain (_Sp) is best developed on PINJIN, and is characterized by eolian reworking of sand to form locally prominent dunes with remnants of lake deposits. Yellow sand with zones of pisolitic gravel, ferruginized silcrete, silt, and clay (_S-l) is derived from ferruginous or siliceous duricrust developed over a granitic substrate, with only a minor eolian component. On Landsat TM 741 images, these largely residual deposits are shown as purple-brown, and are readily distinguished from dark-green, quartz-rich sandplain areas.

Economic geologyGold and nickel are the principal mineral commodities produced in the region covered by the EYGD. As outlined in the summary of data themes in the database, the themes WAMIN, MINEDEX, and TENGRAPH provide mineral occurrence locality, resource, and tenement information, respectively, for the database area. These layers encompass the large number of both historical and current mine sites, and continuing prospecting activity. Details of exploration activities recorded in open-fi le statutory mineral exploration reports are stored in DoIR’s Western Australian mineral exploration database (WAMEX). At the time of writing, more than 10 000 reports were publicly accessible from the Perth and Kalgoorlie offi ces of DoIR, with recent reports available online through DoIR’s website (www.doir.wa.gov.au). The MINEDEX database and annual publications such as the DoIR Statistics Digest provide resource and production statistics. Flint (2002) and Flint and Searston (2004) provided recent exploration and development statistics. Brief overviews of the commodities that are present and have been exploited in the EGGGT are presented below.

GoldThe discovery of gold at Coolgardie and Kalgoorlie in the early 1890s led to European settlement of the area now known as the Eastern Goldfi elds. Exploration in the region led to the early establishment of several gold mining centres, with gold production increasing to a peak of about 2 Moz in 1903, followed by a steady decline in the 1920s, a minor resurgence in the 1930s, and a further decline in the 1960s and 1970s. Production increased dramatically in the 1980s and 1990s, reaching a peak of 7.7 Moz in 1997, before declining slightly to 6 Moz in 2003.

Most gold deposits in the EGGGT region are fracture controlled, and near major zones of faulting and shearing within and at the margins of the greenstone belts, predominantly in mafi c greenschist-facies metavolcanic rocks or in gabbro. Gold is either within quartz-vein sets or in surrounding alteration zones. The continuum model of Groves (1993) and Solomon and Groves (1994) interprets gold deposits of varying characteristics as having formed throughout the middle to the upper crust, adjacent to


3

crustal-scale plumbing systems, in response to a massive fl uid fl ux; this model has been largely adopted for the bulk of gold mineralization in the Eastern Goldfi elds region. More recently, gold deposits of the Eastern Goldfi elds region were identified as late-orogenic structurally controlled deposits (Witt and Vanderhor, 1998), and Groves et al. (1998) classifi ed them as ‘orogenic gold deposits’.

The most common host rocks in the EGGGT (basalt, gabbro, dolerite, and BIF) have high Fe:(Fe+Mg) values, are of middle to upper greenschist facies, and show evidence that transitional brittle–ductile deformation occurred at depths between 6 and 12 km. The deposits are also present in komatiites, intermediate to felsic volcanic or intrusive rocks, and sedimentary rocks. The host rocks are metamorphosed, with metasomatic addition of SiO2, K2O, CO2, H2O, S, and Au. Gold is commonly associated with relatively low accumulations of As, Ag, W, Sb, Te, B, Cu, Pb, Zn, and Mo. Fluid sources may have been either metamorphic or magmatic, or a combination of both. In general, it is believed that gold deposition was controlled by fl uid – wall-rock reactions, such as the sulfi dation of iron-rich hosts, and hence the favouring of rock types with a high Fe:Mg ratio (Groves et al., 1990).

Evidence from gold mines throughout the EGGGT suggests that a regional mineralizing event at 2650–2630 Ma was responsible for deposition of the vast bulk of the gold in terms of tonnage, with volumetrically less-signifi cant mineralizing events at about 2.66 and 2.63 Ga (Solomon and Groves, 1994; Witt et al. 1996; Yeats and McNaughton, 1997). Recent dating from the Yandal greenstone belt, however, indicates that at least some gold mineralization occurred after 2.68 Ga and before 2.66 Ga (Yeats et al., 2000).

Recent discoveries of gold deposits in the Eastern Goldfields region, particularly those in the Yandal greenstone belt, are largely the result of advances in remote sensing and regolith sampling and analysis. Rotherham (2000) noted that at the Mount Joel prospect in the Yandal greenstone belt the transported material overlying the deposit is typically barren, whereas residual material retains or concentrates gold grades present in underlying fresh rock. This highlights the importance of distinguishing regolith type (e.g. Phang and Anand, 2000) in gold exploration, particularly in a deeply weathered region like the north Eastern Goldfi elds.

Gold is also present in the ferricretes and supergene zones that overlie many gold occurrences and deposits in the EGGGT, to the extent that development in many of the early workings did not go far beyond the ‘laterite ore’ (Davy and Gozzard, 1994). In some instances only the laterite ore has been exploited because grades in underlying fresh rock were not economic (Ferguson, 1998).

Placer gold deposits are rare — those that have been recognized are commonly eluvial deposits adjacent to known primary or lateritic gold mineralization. Placer deposits that have been exploited recently include The Patch and Famous Blue in the Duketon greenstone belt, and deposits in the Darlot mining centre in the Yandal greenstone belt.


1

Nickel and cobaltSince the discovery of nickel mineralization in the Lunnon shoot at Kambalda in 1966, ores of this metal have been mined at numerous localities in the region, with the most signifi cant production recorded in the Kambalda region of the southern Eastern Goldfi elds and in the Mount Keith area of the Agnew–Wiluna greenstone belt. Much of the nickel mined until very recently has been in the form of sulfi de associated with large fl ows of high-temperature, high-Mg komatiitic lava (Barnes et al., 1987; Hill et al., 1990; Hill et al., 1996). These authors interpreted the komatiite- and dunite-associated nickel deposits in the Eastern Goldfi elds as extrusive in origin, and subdivided them into two types. In the fi rst type the komatiite fl ows are thin (20–100 m), with mineralization in the form of massive sulfi des (2–15% nickel) and olivine–sulfi de cumulates (about 2.5% nickel) at the base of lava-fl ow channels in komatiite fl ow fi elds. In the second type, disseminated sulfi des are present in the central zones of large bodies of olivine cumulate that occupy broader, more continuous sheet fl ows within erosional pathways or subvolcanic lava feeder zones. They range from olivine–sulfi de orthocumulate to olivine–sulfi de adcumulate, with grades averaging 0.6% nickel (reaching a maximum of 1.5% nickel). Although some primary lithological characteristics are recognizable in all the nickel sulfi de deposits, the host rocks are completely serpentinized and variably carbonatized. Locating such deposits requires detailed interpretation of the fl ow-fi eld stratigraphy and morphology from mapping and drilling, in an environment affected by complex structural reworking of the original volcanic deposits and the effects of deep weathering.

The Type 1 deposits at Kambalda have been among the richest komatiite-hosted nickel sulfi de deposits in the world. Copper, cobalt, platinum-group metals, and gold have been important byproducts. Although some mines have faced diffi culties during times of low nickel price, komatiite-hosted sulfi des are still being mined profi tably. High-grade deposits, such as Silver Swan, can be particularly profi table. The world’s largest Type 1 deposit, forming the Perseverance and Rockys Reward mineralization in the Agnew–Wiluna greenstone belt, has yielded more than 14 Mt of ore at grades exceeding 2% nickel (De-Vitry et al., 1998; Libby et al., 1998). The Mount Keith deposit is a good example of a large-tonnage, low-grade disseminated-sulfi de Type 2 ore deposit, with more than 400 Mt of ore at a grade of 0.6% nickel (Hopf and Head, 1998).

The only important nickel sulfi de deposit not associated with komatiite is that at Carr Boyd Rocks, where sulfi des were mined from an intrusive breccia pipe within a larger peridotite–gabbro complex. Proterozoic mafi c dykes have also been of interest in nickel exploration, with detailed study of the Jimberlana Dyke east of Norseman revealing some subeconomic occurrences.

Deep weathering in the EGGGT has also led to the formation of lateritic nickel deposits, whose economic signifi cance increased during the 1990s. Laterite nickel(–cobalt) resources are presently being exploited in the Menzies to Norseman region, where they are developed


32

above or adjacent to ultramafi c rock types, and thus refl ect the abundance of komatiites and the preservation of their weathering profi les. Nickel is extracted at Murrin Murrin, Cawse, and Bulong using high-temperature and high-pressure acid-leach processes, which allow for economical production from low-grade deposits.

Nickel–cobalt laterite mineralization in the Eastern Goldfi elds is derived from in situ chemical weathering of serpentinized komatiite, with the metals concentrated within various transitional minerals that are stable in near-surface conditions (Burger, 1996). The lateritic nickel–cobalt deposits of the Yilgarn Craton have a prolonged weathering history and, compared to other deposits elsewhere, have higher smectite and silica (chalcedony, chert) contents, coincident nickel and cobalt maxima relatively high in the weathering profi le, nickel-poor saprolite, and complex internal geometries (Burger, 1996). Typically, nickel–cobalt laterite deposits of the Yilgarn Craton contain, at surface, a dense hematite-rich duricrust that overlies a heterogeneous ferruginous zone dominated by siliceous goethite, limonite, and limonitic clay in varying proportions (Burger, 1996). Beneath this is a smectite zone containing nickeliferous smectite clay minerals. At the base of the regolith profi le is the saprolite zone. The thickness of these zones varies between deposits in the region, presumably related to variations in host mineralogy and the extent of leaching.

Base metalsDespite extensive exploration, economic volcanic-hosted massive sulfi de (VHMS)-style mineralization is rare in the EGGGT (Ferguson, 1998). Although felsic volcanogenic rocks may amount to around 40% of the Eastern Goldfi elds greenstones, and have some characteristics in common with mineralized felsic rocks in greenstones of the Abitibi and Superior Provinces from Canada, exploration to date has located only a few economic base-metal deposits. Comparison of trace-element signatures of the felsic volcanic sequences in the Eastern Goldfi elds region and the base-metal-rich Canadian Abitibi and Superior greenstones suggests a rather low potential for VHMS mineralization in the Eastern Goldfi elds (Witt et al., 1996; Messenger, 2000).

The 2.5 Mt copper–zinc deposit at Teutonic Bore, near the southern limit of the Yandal greenstone belt 55 km north-northwest of Leonora, is the largest and most recently mined (1980 to 1984) VHMS-style deposit of the region. The deposit consists of a single lens of massive to banded sulfi de hosted by pyritic black shale and siltstone, with crosscutting stringer mineralization in the basaltic and felsic volcanic–volcaniclastic footwall representing the feeder (Greig, 1984). Strong quartz–chlorite–carbonate–sericite alteration is present in the feeder zone. Greig (1984) considered that the deposit formed on the fl anks of a rhyolite dome, with sulfi de accumulation in a palaeotopographic low. The Kilkenny Syncline, about 45 km east of Leonora, contains minor VHMS deposits. The mineralized horizon is characterized by black shale, greywacke, and siltstone (probably of volcaniclastic origin) that overlies rhyodacitic volcanic and volcaniclastic

rocks, and is overlain by pillow basalt (Ferguson, 1998). The deposits represent venting of hydrothermal fl uids onto the sea fl oor or infi ltration of fl uids below the sediment–water interface or both, and alteration and vent zones are recognized.

Copper was mined in the Kathleen Valley area between 1909 and 1967, yielding 420 t of copper from pyrite–chalcopyrite–quartz veins (Liu et al., 1998). The copper mineralization, commonly with some associated gold and silver, is spatially related to north-northwesterly trending shear zones in the Kathleen Valley Intrusion gabbro and Mount Goode Basalt (Bunting and Williams, 1979). Gold-bearing pyrite–chalcopyrite–quartz veins contain traces of copper. A small amount has been produced from shales in the hangingwall of the Mount Pleasant sill, and from chalcopyrite-bearing quartz veins at Corsair, about 10 km east of Kalgoorlie.

Other commodities

Iron and manganese

Manganese and iron have been mined at Mount Lucky, 20 km southeast of Laverton, where psilomelane and pyrolusite are associated with jaspilite and BIF (Lord and de la Hunty, 1950; Tomich, 1956). Historic production was not recorded, but a small resource is present (Painter et al., 2003, table 5).

Another possible resource is the abundant granular iron-formation and ferruginous shale of the Frere Formation in the Earaheedy Basin. Quartz – iron oxide –manganese oxide veins and stratiform iron- and manganese-oxide bands are present in the Chiall and Wongawol Formations respectively (Pirajno and Adamides, 2000). Iron enrichment is a local result of either hydrothermal alteration proximal to fault zones or chemical weathering processes (Hocking and Jones, 1999). The Frere Formation is exposed on BALLIMORE and DE LA POER, and extends northward at depth beneath the stratigraphically higher units of the Earaheedy Basin.

Uranium

Calcrete-hosted uranium deposits are in the Tertiary palaeodrainage systems of the northern and centralEGGGT. Carnotite (K2(UO2)2(VO4)2

.1–3H2O) forms coatings and fi llings within the calcrete (Langford, 1974). Most of the deposits are on WILUNA (Lake Way, Hinkler Well, Abercromby Well), but the Lake Maitland deposit is on WANGGANNOO and the Yeelirrie deposit lies just west of the area covered by the database. Although the deposits may be economically signifi cant (Keats, 1990), none has been exploited.

Tin

There is a minor tin occurrence southwest of the Kathleen Valley townsite. The cassiterite-bearing pegmatite was worked between 1945 and 1953 (Bunting and Williams, 1979). Minor occurrences of tin, in the form


of a cassiterite-bearing lepidolite–albite pegmatite, were worked in the Norseman area between 1966 and 1968, yielding about 7 t of concentrate (Doepel, 1973).

Diamonds

Much of the database area has been explored for diamonds, and several kimberlitic bodies have been identifi ed, with several diamonds recovered. No economic resource has been discovered.

Magnesium

Magnesite is commonly spatially associated with lateritic nickel–cobalt deposits of the EGGGT. Topographically, the magnesium mineralization is typically downstream from, and in a lower topographic position than, the genetically related nickel–cobalt laterite. Magnesium resources have been identifi ed at Marshall Pool, Murrin Murrin, White Eagle, and Joes Bore east of Lawlers.

Phosphate, rare earth elements, niobium, and tantalum

The Mount Weld phosphate, rare earth element, niobium, and tantalum deposits overlie the 2021 ± 13 Ma Mount Weld carbonatite, which is a cylindrical, predominantly sövitic intrusion 4 km in diameter that has intruded the Laverton greenstone belt (Duncan and Willett, 1990). The carbonatite is not exposed; almost all resources are in the karst-like regolith above the carbonatite, which is now covered by more recent alluvial material (Duncan and Willett, 1990). Residual apatite forms a continuous 6–30 m-thick sheet directly overlying fresh carbonatite. Residual concentrates of primary magmatic phases, such as pyrochlore, ilmenite, and niobian rutile, above the apatite zone contain subeconomic concentrations of niobium and tantalum. Rare earth elements are present in primary magmatic phases (monazite, apatite, synchysite) dispersed throughout the carbonatite regolith. Local concentrations of secondary monazite contain very high proportions of lanthanides (up to 45% lanthanide oxides; Duncan and Willett, 1990).

Tungsten

Scheelite is a common accessory mineral in many gold deposits of the EGGGT (Ghaderi et al., 1999). At gold workings around the Comet Vale mining centre, scheelite is in quartz–calcite veins and the surrounding amphibolites (Simpson, 1952), and this area has produced more tungsten than the rest of the Eastern Goldfi elds (Baxter, 1978). Scheelite concentrates have been recovered as a byproduct of gold processing at Coolgardie, Davyhurst, and Higginsville. Patchy scheelite mineralization is associated with 30 × 0.75 m quartz lenses in strongly metamorphosed mafi c rocks 1.5 km east-southeast of Ogilvies gold workings, near Mount Amy (Berliat, 1954; Gower, 1976). Tungsten has been mined, as wolframite, from the quartz and pegmatite veins around Ora Banda.

33


Molybdenum

Molybdenite is present in pegmatite at the Mount Molybdenite (Thomas’ Show) occurrence and in reaction zones adjacent to porphyry dykes at South Windarra (Baxter, 1978). There is no recorded production from the Eastern Goldfi elds.

Bismuth

Hallberg (1985) noted the common occurrence of bismuth in gold deposits around Niagara. Several sulfi des of bismuth, copper, and lead are present at the Teutonic Bore VHMS deposit (Greig, 1984).

Lithium–tantalum–beryl

The Londonderry and Spargoville pegmatites on YILMIA have yielded almost 8000 t of petalite, 300 t of beryl, 130 t of lepidolite, and 9 t of tantalite–columbite.

Semiprecious gemstones

Chrysoprase is associated with silica caprock over ultramafi c rocks. Several prospects have been identifi ed at Marshall Creek, Murrin Murrin, and near Eucalyptus. Chrysoprase has been mined on a small scale from several localities, but there are no records of production.

Small occurrences of lace and honey opal have been reported 3 km north of Pyke Well on Yundamindera Station (Williams et al., 1976). Moss opal was mined on a small scale with chrysoprase near Eucalyptus (Hallberg, 1985).


References

34

ADAMIDES, N. G., FARRELL, T., and PIRAJNO, F., 1998, Cunyu, W.A. Sheet 2945 (1st edition): Western Australia Geological Survey, 1:100 000 Geological Series.

ADAMIDES, N. G., FARRELL, T., and PIRAJNO, F., 1999, Geology of the Cunyu 1:100 000 sheet: Western Australia Geological Survey, 1:100 000 Geological Series Explanatory Notes, 21p.

AHMAT, A. L., 1993, Mafi c–ultramafi c rocks of the Gindalbie Terrane: a review of the Bulong and Carr Boyd Complexes, in An international conference on crustal evolution, metallogeny and exploration in the Eastern Goldfi elds, Extended Abstracts compiled by P. R. WILLIAMS and J. A. HALDANE: Canberra, Australian Geological Survey Organisation, Record 1993/54, p. 23–27.

AHMAT, A. L., 1995a, Geology of the Kanowna 1:100 000 sheet: Western Australia Geological Survey, 1:100 000 Geological Series Explanatory Notes, 28p.

AHMAT, A. L., 1995b, Gindalbie, W.A. Sheet 3237: Western Australia Geological Survey, 1:100 000 Geological Series.

AHMAT, A. L., 1995c, Kanowna, W.A. Sheet 3236: Western Australia Geological Survey, 1:100 000 Geological Series.

ALLCHURCH, P. D., and BUNTING, J. A., 1976, The Kaluweerie Conglomerate: a Proterozoic fl uviatile sediment from the Yilgarn Block: Western Australian Geological Survey, Annual Report 1975, p. 83–87.

ANAND, R. R., 2000, Regolith and geochemical synthesis of the Yandal greenstone belt, in Yandal Greenstone Belt: regolith, geology and mineralization edited by G. N. PHILLIPS and R. R. ANAND: Australian Institute of Geoscientists, Bulletin, no. 32, p. 79–111.

ANAND, R. R., CHURCHWARD, H. M., SMITH, R. E., SMITH, K., GOZZARD, J. R., CRAIG, M. A., and MUNDAY, T. J., 1993, Classifi cation and atlas of regolith-landform mapping units: Australia CSIRO, AMIRA Project P240A, Exploration and Mining Restricted Report 440R (unpublished).

ANAND, R. R., and PAINE, M., 2002, Regolith geology of the Yilgarn Craton, Western Australia: implications for exploration: Australian Journal of Earth Sciences, v. 49, p. 3–162.

ARCHIBALD, N. J., BETTENAY, L. F., BICKLE, M. J., and GROVES, D. I., 1981. Evolution of Archaean crust in the Eastern Goldfi elds Province of the Yilgarn Block: Geological Society of Australia, Special Publication 7, p. 491–504.

ARNDT, H. T., and JENNER, G. A., 1986, Crustally contaminated komatiites and basalts from Kambalda, Western Australia: Chemical Geology, v. 56, p. 229–255.

BAGAS, L., and SMITHIES, R. H., 1998, Geology of the Connaughton 1:100 000 sheet: Western Australia Geological Survey, 1:100 000 Geological Series Explanatory Notes, 38p.

BARLEY, M. E., 1986, Incompatible-element enrichment in Archean basalts: a consequence of contamination by older sialic crust rather than mantle heterogeneity: Geology, v. 14, p. 947–950.

BARLEY, M. E., EISENLOHR, B. N., GROVES, D. I., PERRING, C. S., and VEARNCOMBE, J. R., 1989, Late Archean convergent margin tectonics and gold mineralization: a new look at the Norseman–Wiluna belt, Western Australia: Geology, v. 17, p. 826–829.

BARNES, S. J., GOLE, M. J., and HILL, R. E. T., 1987, The Agnew nickel deposit, Yilgarn Block, Western Australia: stratigraphy, structure, geochemistry and origin: Perth, Western Australian Minerals and Petroleum Research Institute, Report no. 38, 187p.

BAXTER, J. L., 1978, Molybdenum, tungsten, vanadium and chromium in Western Australia: Western Australia Geological Survey, Mineral Resources Bulletin 11, 140p.

BERLIAT, K., 1954, Report on Laverton scheelite prospect P.A.2548T, P.A.2554T, P.A.2555T, Laverton, Mt Margaret Goldfi eld: Western Australia Geological Survey, Annual Report 1951, p. 32.

BETTENAY, L. F., 1988, The nature and origin of batholithic granitoids in the Yilgarn Block, Western Australia, and their signifi cance to gold mineralization, in Advances in understanding Precambrian gold deposits, Volume 2 edited by S. E. HO and D. I. GROVES:University of Western Australia, Geology Department and University Extension, Publication no. 12, p. 227–237.

BLAKE, D., and WHITAKER, A. J., 1996a, Ballimore, W.A. Sheet 3145 (preliminary edition): Canberra, Australian Geological Survey Organisation, 1:100 000 Geological Series.

BLAKE, D., and WHITAKER, A. J., 1996b, Sandalwood, W.A. Sheet 3144 (preliminary edition): Canberra, Australian Geological Survey Organisation, 1:100 000 Geological Series.

BLEWETT, R. S., CASSIDY, K. F., CHAMPION, D. C., HENSON, P. A., GOLEBY, B. S., JONES, L., and GROENEWALD, P. B., 2004, The Wangkathaa Orogeny: an example of episodic regional ‘D2’ in the late Archaean Eastern Goldfi elds Province, Western Australia:Precambrian Research, v. 130, p. 139–159.

BROWN, S. J., KRAPEZ, B., BERESFORD, S. W., CASSIDY, K. F., CHAMPION, D. C., BARLEY, M. E., and CAS, R. A. F., 2001, Archaean volcanic and sedimentary environments of the Eastern Goldfi elds Province, Western Australia — a fi eld guide: Western Australia Geological Survey, Record 2001/13, 66p.

BUNTING, J. A., and WILLIAMS, S. J., 1979, Sir Samuel, W.A. (1st edition): Western Australia Geological Survey, 1:250 000 Geological Series Explanatory Notes, 40p.

BURGER, P., 1996, Origins and characteristics of lateritic nickel deposits, in Nickel ’96; Mineral to Market edited by E. J. GRIMSEY and I. NEUSS: The Australasian Institute of Mining and Metallurgy, Report 6/96, p. 179–183.

BUTT, C. R. M., 1985, Granite weathering and silcrete formation on the Yilgarn Block, Western Australia: Australian Journal of Earth Sciences, v. 32, p. 415–432.

CAMPBELL, I. H., 1968, The origin of heteradcumulate and adcumulate textures in the Jimberlana Norite: Geological Magazine, v. 105, p. 378–383.

CAMPBELL, I. H., 1978, Some problems with cumulus theory: Lithos, v. 11, p. 311–328.

CAMPBELL, I. H., and HILL, R. I., 1988, A two-stage model for the formation of the granite–greenstone terrains of the Kalgoorlie–Norseman area, Western Australia: Earth and Planetary Science Letters, v. 90, p. 11–25.

CHAMPION, D. C., 1996, Tate, W.A. Sheet 3243 (preliminary edition): Canberra, Australian Geological Survey Organisation, 1:100 000 Geological Series.


35

CHAMPION, D. C., and CASSIDY, K. F., 2002, Granites in the Leonora–Laverton transect area, northeastern Yilgarn Craton: Canberra, Geoscience Australia, Record 2002/18, p. 13–35.

CHAMPION, D. C., and SHERATON, J. W., 1993, Geochemistry of granitoids of the Leonora–Laverton region, Eastern Goldfi elds Province, in Kalgoorlie 93 — an international conference on crustal evolution, metallogeny, and exploration of the Eastern Goldfi elds compiled by P. R. WILLIAMS and J. A. HALDANE: Canberra, Australian Geological Survey Organisation, Record 1993/54, p. 39–46.

CHAMPION, D. C., and SHERATON, J. W., 1997, Geochemistry and Nd isotope systematics of Archaean granites of the Eastern Goldfi elds, Yilgarn Craton, Australia: implications for crustal growth processes: Precambrian Research, v. 83, p. 109–132.

CHAMPION, D. C., and SMITHIES, R. H., 2001, Archaean granites of the Yilgarn and Pilbara cratons, Western Australia, in 4th International Archaean Symposium 2001, Extended Abstracts edited by K. F. CASSIDY, J. M. DUNPHY, and M. J. VAN KRANENDONK: Canberra. AGSO – Geoscience Australia, Record 2001/37, p. 134–136.

CHAMPION, D. C., and STEWART, A. J., 1996a, McMillan, W.A. Sheet 3441 (preliminary edition): Canberra, Australian Geological Survey Organisation, 1:100 000 Geological Series.

CHAMPION, D. C., and STEWART, A. J., 1996b, Urarey, W.A. Sheet 3343 (preliminary edition): Canberra, Australian Geological Survey Organisation, 1:100 000 Geological Series.

CHAMPION, D. C., and STEWART, A. J., 1998, Yeelirrie, W.A. Sheet 2943 (preliminary edition): Canberra, Australian Geological Survey Organisation, 1:100 000 Geological Series.

CHEN, S. F., and WITT, W. K., 1998, Boyce, W.A.: Western Australia Geological Survey, 1:100 000 Geological Series.

CHEN, S. F., WITT, W., and LIU, S. F., 2001, Transpressional and restraining jogs in the northeastern Yilgarn Craton, Western Australia: Precambrian Research, v. 106, p. 309–328.

CHEN, S. F., WYCHE, S., and RIGANTI, A., 2003, Comparison of lithostratigraphy and tectonic history across the Yilgarn Craton: Specialist Group in Tectonics and Structural Geology Field Meeting, Kalbarri, W.A., 2003; Geological Society of Australia, Abstracts, no. 72, p. 51.

CLARKE, J. D. A., 1994, Evolution of the Lefroy and Cowan palaeodrainage channels, Western Australia: Australian Journal of Earth Sciences, v. 41, p. 55–68.

CLOUT, J. M. F., CLEGHORN, J. H., and EATON, P. C., 1990, Geology of the Kalgoorlie gold fi eld, in Geology of the mineral deposits of Australia and Papua New Guinea, Volume 1 edited by F. E. HUGHES: The Australasian Institute of Mining and Metallurgy, Monograph 14, p. 411–431.

COCKBAIN, A. E., 1968a, Eocene foraminifera from the Norseman Limestone of Lake Cowan, Western Australia: Western Australia Geological Survey, Annual Report 1967, p. 59–60.

COCKBAIN, A. E., 1968b, The stratigraphy of the Plantagenet Group, Western Australia: Western Australia Geological Survey, Annual Report 1967, p. 61–63.

COMPSTON, W., WILLIAMS, I. S., CAMPBELL, I. H., and GRESHAM, J. J., 1986, Zircon xenocrysts from the Kambalda volcanics: age constraints and direct evidence for older continental crust below the Kambalda–Norseman greenstones: Earth and Planetary Science Letters, v. 76, p. 299–301.

DAVIS, B. K., and MAIDENS, E., 2003, Archaean orogen-parallel extension: evidence from the northern Eastern Goldfi elds Province, Yilgarn Craton: Precambrian Research, v. 127, p. 229–248.

DAVY, R., and GOZZARD, J. R., 1995, Lateritic duricrusts of theLeonora area, Eastern Goldfi elds, Western Australia: a contribution to the study of transported laterites: Western Australia Geological Survey, Record 1994/8, 122p.

DE-VITRY, C., LIBBY, J. W., and LANGWORTHY, P. J., 1998, Rocky’s Reward nickel deposit, in Geology of Australian and Papua New Guinean mineral deposits edited by D. A. BERKMAN and D. H. MACKENZIE: The Australasian Institute of Mining and Metallurgy, Monograph 22, p. 315–320.

DOEPEL, J. J. G., 1973, Norseman, W.A.: Western AustraliaGeological Survey, 1:250 000 Geological Series Explanatory Notes. 40p.

DRUMMOND, B. J., GOLEBY, B. R., SWAGER, C. P., and WILLIAMS, P. R., 1993, Constraints on Archaean crustal composition and structure provided by deep seismic sounding in the Yilgarn Block: Ore Geology Reviews, v. 8, p. 117–124.

DUGGAN, M. B., 1995a, Burtville, W.A. Sheet 3440 (preliminary edition): Canberra, Australian Geological Survey Organisation, 1:100 000 Geological Series.

DUGGAN, M. B., 1995b, McMillan, W.A. Sheet 3441 (preliminary edition): Canberra, Australian Geological Survey Organisation, 1:100 000 Geological Series.

DUGGAN, M. B., 1995c, Mount Alexander, W.A. Sheet 2940 (preliminary edition): Canberra, Australian Geological Survey Organisation, 1:100 000 Geological Series.

DUGGAN, M. B., 1995d, Mount Celia, W.A. Sheet 3439 (preliminary edition): Canberra, Australian Geological Survey Organisation, 1:100 000 Geological Series.

DUGGAN, M. B., WHITAKER, A. J., and BASTRAKOVA, I. V., 1996a, Wilbah, W.A. Sheet 3040: Canberra, Australian Geological Survey Organisation, 1:100 000 Geological Series.

DUGGAN, M. B., WILLIAMS, P. R., and OVERSBY, B. S., 1996b, Munjeroo, W.A. Sheet 2941 (2nd edition): Canberra, Australian Geological Survey Organisation, 1:100 000 Geological Series.

DUNBAR, G. J., and McCALL, G. J. H., 1971, Archaean turbidites and banded ironstones of the Mt Belches area (Western Australia): Sedimentary Geology, v. 5, p. 93–133.

DUNCAN, R. K., and WILLETT, G. C., 1990, Mount Weld carbonatite, in Geology of the mineral deposits of Australia and Papua New Guinea, Volume I edited by F. E. HUGHES: The Australasian Institute of Mining and Metallurgy, Monograph 14, p. 591–597.

FARRELL, T. R., and GRIFFIN, T. J., 1997, Banjawarn, W.A. Sheet 3242 (1st edition): Western Australia Geological Survey, 1:100 000 Geological Series.

FARRELL, T. R., and LANGFORD, R. L., 1996, Duketon, W.A. Sheet 3342 (1st edition): Western Australia Geological Survey, 1:100 000 Geological Series.

FARRELL, T. R., and WYCHE, S., 1997, Millrose, W.A. Sheet 3045 (1st edition): Western Australia Geological Survey, 1:100 000Geological Series.

FARRELL, T. R., and WYCHE, S., 1999, Geology of the Millrose 1:100 000 sheet: Western Australia Geological Survey, 1:100 000 Geological Series Explanatory Notes, 29p.

FERGUSON, K. M., 1998, Mineral occurrences and explorationpotential of the north Eastern Goldfields: Western AustraliaGeological Survey, Report 63, 40p.

FLETCHER, I. R., DUNPHY, J. M., CHAMPION, D. C., and CASSIDY, K. F., 2001, Compilation of SHRIMP U–Pb geochronology data, Yilgarn Craton, Western Australia, 2000–2001: Canberra, Geoscience Australia, Record 2001/47, 109p.

FLINT, D. J., 2002, Overview of the mineral sector in Western Australia in 2000–01: Western Australia Geological Survey, 8p.

FLINT, D. J., and SEARSTON, S. M., 2004, Western Australian mineral exploration and development in 2001 and 2002: Western Australia Geological Survey, Report 94, 74p.


36

GEE, R. D., BAXTER, J. L., WILDE, S. A., and WILLIAMS, I. R., 1981, Crustal development in the Yilgarn Block, Western Australia, in Archaean Geology — Second International Symposium, Perth, W.A., 1980 edited by J. E. GLOVER and D. I. GROVES: Geological Society of Australia, Special Publication no. 7, p. 275–286.

GEE, R. D., and GREY, K., 1993, Proterozoic rocks of the Glengarry 1:250 000 sheet — stratigraphy, structure, and stromatolite biostratigraphy: Western Australia Geological Survey, Report 41, 30p.

GEOLOGICAL SURVEY OF WESTERN AUSTRALIA, 2004, Compilation of geochronology data, 1994–2001: Western Australia Geological Survey, Record 2003/2.

GHADERI, M., PALIN, J. M., CAMPBELL, I. H., and SYLVESTER, P. J., 1999, Rare earth element systematics in scheelite from hydrothermal gold deposits in the Kalgoorlie–Norseman region, Western Australia: Economic Geology, v. 94, p. 423–437.

GILES, C. W., 1980, A comparative study of Archaean and Proterozoic felsic volcanic associations in southern Australia: South Australia, University of Adelaide, PhD thesis (unpublished).

GILES, C. W., 1982, The geology and geochemistry of the Archaean Spring Well felsic volcanic complex, Western Australia: Geological Society of Australia, Journal, v. 29, p. 205–220.

GOLEBY, B. R., BLEWETT, R. S., GROENEWALD, P. B., CASSIDY, K. F., CHAMPION, D. C., JONES, L. E. A., KORSCH, R. J., SHEVCHENKO, S., and APAK, S. N., 2003, The 2001 Northeastern Yilgarn Deep Seismic Refl ection Survey: Canberra, Geoscience Australia, Record 2003/28, 144p.

GOLEBY, B. R., RATTENBURY, M. S., SWAGER, C. P.,DRUMMOND, B. J., WILLIAMS, P. R., SHERATON, J. E., and HEINRICH, C. A., 1993, Archaean crustal structure from seismic refl ection profi ling, Eastern Goldfi elds, Western Australia: Canberra, Australian Geological Survey Organisation, Record 1993/15, 54p.

GOWER, C. F., 1976, Laverton, W.A. (1st edition): Western Australia Geological Survey, 1:250 000 Geological Series Explanatory Notes, 30p.

GREIG, D. D., 1984, Geology of the Teutonic Bore massive sulphide deposit, Western Australia: The Australasian Institute of Mining and Metallurgy, Proceedings, 289, p. 147–156.

GRESHAM, J. J., and LOFTUS-HILLS, G. D., 1981, The geology of the Kambalda nickel fi eld, Western Australia: Economic Geology, v. 76, p. 1373–1416.

GRIFFIN, T. J., 1988, Cowan, W.A. Sheet 3234: Western Australia Geological Survey, 1:100 000 Geological Series.

GRIFFIN, T. J., 1990a, Eastern Goldfi elds Province, in Geology and mineral resources of Western Australia: Western Australia Geological Survey, Memoir 3, p. 77–119.

GRIFFIN, T. J., 1990b, Geology of the granite–greenstone terrane of the Lake Lefroy and Cowan 1:100 000 sheets, Western Australia: Western Australia Geological Survey, Report 32, 53p.

GRIFFIN, T. J., and FARRELL, T. R., 1998, Cosmo Newbery, W.A. Sheet 3442 (1st edition plot): Western Australia Geological Survey, 1:100 000 Geological Series.

GRIFFIN, T. J., and HICKMAN, A. H., 1988, Lake Lefroy, W.A. Sheet 3235: Western Australia Geological Survey, 1:100 000 Geological Series.

GROENEWALD, P. B., and DOYLE, M., 2004, Volcanological reconstruction of felsic–ultramafi c sequences in the Minerie area, Yilgarn Craton, Western Australia: 17th Australian Geological Convention, Hobart, Tasmania, 2004; Geological Society of Australia, Abstracts no. 73, p. 270.

GROENEWALD, P. B., MORRIS, P. A., and CHAMPION, D. C., 2003, Geology of the Eastern Goldfi elds and an overview of tectonic models, in The 2001 Northeastern Yilgarn Deep Seismic Refl ection

Survey edited by B. R. GOLEBY, R. S. BLEWETT, P. B. GROENEWALD, K. F. CASSIDY, D. C. CHAMPION, L. E. A. JONES, R. J. KORSCH, S. SHEVCHENKO, and S. N. APAK: Canberra, Geoscience Australia, Record 2003/28, p. 63–84.

GROENEWALD, P. B., PAINTER, M. G. M., and McCABE, M., 2001, East Yilgarn Geoscience Database, 1:100 000 geology of the north Eastern Goldfi elds Province — an explanatory note: Western Australia Geological Survey, Report 83, 39p.

GROENEWALD, P. B., PAINTER, M. G. M., ROBERTS, F. I., McCABE, M., and FOX, A., 2000, East Yilgarn Geoscience Database, 1:100 000 geology Menzies to Norseman — an explanatory note: Western Australia Geological Survey, Report 78, 53p.

GROVES, D. I., 1993, The crustal continuum model for late-Archaean lode-gold deposits of the Yilgarn Block, Western Australia: Mineralium Deposita, v. 28, p. 366–374.

GROVES, D. I., GOLDFARB, R. J., GEBRE-MARIAM, M., HAGEMANN, S. G., and ROBERT, F., 1998, Orogenic gold deposits: a proposed classifi cation in the context of their crustal distribution and relationship to other gold deposit types: Ore Geology Reviews, 13, p. 1–27.

GROVES, D. I., KNOX-ROBINSON, C. M., HO, S. E., and ROCK, N. M. S., 1990, An overview of Archaean lode-gold deposits: University of Western Australia, Geology Department (Key Centre) and University Extension, Publication no. 20, p. 2–18.

HALILOVIC, J., CAWOOD, P. A., JONES, A. J., PIRAJNO, F., and NEMCHIN, A. A., 2004, Provenance of the Earaheedy Basin: implications for assembly of the Western Australian Craton: Precambrian Research, v. 128, p. 343–366.

HALL, W. D. M., GOODE, A. D. T., BUNTING, J. A., and COMMANDER, D. P., 1977, Stratigraphic terminology of the Earaheedy Group, Nabberu Basin: Western Australia Geological Survey, Annual Report 1976, p. 40–43.

HALLBERG, J. A., 1985, Geology and mineral deposits of the Leonora–Laverton area, northeastern Yilgarn Block, Western Australia: Perth, Western Australia, Hesperian Press, 140p.

HALLBERG, J. A., 1987, Postcratonization mafi c and ultramafi c dykes of the Yilgarn Block: Australian Journal of Earth Sciences, v. 34, p. 135–149.

HAMMOND, R. L., and NISBET, B. W., 1992, Towards a structural and tectonic framework for the Norseman–Wiluna Greenstone Belt, Western Australia, in The Archaean: terrains, processes and metallogeny edited by J. E. GLOVER and S. E. HO: University of Western Australia, Geology Department (Key Centre) and University Extension, Publication no. 22, p. 39–50.

HILL, R. E. T., BARNES, S. J., and DOWLING, S. E., 2001, Komatiites of the Norseman–Wiluna Greenstone Belt, Western Australia — a fi eld guide: Western Australia Geological Survey, Record 2001/10, 71p.

HILL, R. E. T., BARNES, S. J., and PERRING, C. S., 1996, Komatiite volcanology and the volcanogenic setting of associated nickel deposits, in Nickel ’96: Mineral to market edited by E. J. GRIMSEY and I. NUESS: The Australasian Institute of Mining and Metallurgy, Publication Series no. 6/96, p. 91–95.

HILL, R. E. T., BARNES, S. J., GOLE, M. J., and DOWLING, S. E., 1990, Physical volcanology of komatiites (2nd edition): Geological Society of Australia (W.A. Division), Excursion Guidebook no. 1, 100p.

HILL, R. E. T., BARNES, S. J., GOLE, M. J., and DOWLING, S. J., 1995, The volcanology of komatiites as deduced from fi eld relationships in the Norseman–Wiluna greenstone belt, Western Australia: Lithos, v. 34, p. 159–188.

HILL, R. E. T., GOLE, M. J., and BARNES, S. J., 1989, Olivine adcumulates in the Norseman–Wiluna greenstone belt, Western Australia: implications for the volcanology of komatiites, in Magmatic sulphides — the Zimbabwe Volume edited by


37

M. D. PRENDERGAST and M. J. JONES: London, United Kingdom, The Institution of Mining and Metallurgy, p. 189–206.

HILL, R. I., CAMPBELL, I. H., and COMPSTON, W., 1989, Age and origin of granitic rocks in the Kalgoorlie–Norseman region of Western Australia: implications for the origin of the Archaean crust: Geochimica et Cosmochimica Acta, v. 53, p. 1259–1275.

HILL, R. I., CHAPPELL, B. W., and CAMPBELL, I. H., 1992, Late Archaean granites of the southeastern Yilgarn Block, WesternAustralia: age, geochemistry, and origin: United Kingdom, Royal Society of Edinburgh, Transactions, v. 83, p. 211–226.

HOCKING, R. M., and COCKBAIN, A. E., 1990, Regolith, in Geology and mineral resources of Western Australia: Western Australia Geological Survey, Memoir 3, p. 591–602.

HOCKING, R. M., and JONES, J. A., 1999, Geology of the Methwin 1:100 000 sheet: Western Australia Geological Survey, 1:100 000 Geological Series Explanatory Notes, 35p.

HOCKING, R. M., JONES, J. A., PIRAJNO, F., and GREY, K., 2000, Revised lithostratigraphy for Proterozoic rocks in the Earaheedy Basin and nearby areas: Western Australia Geological Survey, Record 2000/16, 22p.

HOCKING, R. M., LANGFORD, R. L., THORNE, A. M., SANDERS, A. J., MORRIS, P. A., STRONG, C. A., and GOZZARD, J. R., 2001, A classifi cation system for the regolith in Western Australia: Western Australia Geological Survey, Record 2001/4, 22p.

HOPF, S., and HEAD, D. L., 1998, Mount Keith nickel deposit, in Geology of Australian and Papua New Guinean mineral deposits edited by D. A. BERKMAN and D. H. MACKENZIE: Australasian Institute of Mining and Metallurgy, Monograph 22, p. 307–314.

HUNTER, W. M., 1988a, Kalgoorlie, W.A. Sheet 3136: Western Australia Geological Survey, 1:100 000 Geological Series.

HUNTER, W. M., 1988b, Yilmia, W.A. Sheet 3135: Western Australia Geological Survey, 1:100 000 Geological Series.

HUNTER, W. M., 1993, The geology of the granite–greenstone terrane of the Kalgoorlie and Yilmia 1:100 000 sheets, Western Australia: Western Australia Geological Survey, Report 35, 80p.

JAGODZINSKI, E., STEWART, A. J., and CHAMPION, D. C., 1999, Geology, structure, and mineral resources of the Mount Keith 1:100 000 sheet (3043), Western Australia: Canberra, Australian Geological Survey Organisation, Record 1999/37, 31p.

JAGODZINSKI, E., STEWART, A. J., and LIU, S. F., 1997, Mount Keith, W.A. Sheet 3043 (preliminary edition): Canberra, Australian Geological Survey Organisation, 1:100 000 Geological Series.

JAGODINSKI, E., WHITAKER, A. J., and SEDGMEN, A., 1996, Nambi, W.A. Sheet 3241: Canberra, Australian Geological Survey Organisation, 1:100 000 Geological Series.

JONES, J. A., PIRAJNO, F., and HOCKING, R. M., 2000a, A revised stratigraphic framework for the Earaheedy Group: implications for the tectonic evolution and mineral potential of the Earaheedy Basin: Western Australia Geological Survey, Annual Review 1999–2000, p. 57–64.

JONES, J. A., PIRAJNO, F., and HOCKING, R. M., 2000b, Stratigraphy, tectonic evolution, and mineral potential of the Earaheedy Basin: Western Australia Geological Survey, Record 2000/8, p. 11–13.

JONES, S., 2003, Structural interpretation of the Yardilla 1:100 000 sheet: implications for the Yilgarn – Albany Fraser suture: Specialist Group in Tectonics and Structural Geology Field Meeting, Kalbarri, W.A., 2003; Geological Society of Australia, Abstracts, no. 72, p. 68.

JUTSON, J. T., 1934, The physiography (geomorphology) of Western Australia: Geological Survey of Western Australia, Bulletin 95 (reprinted 1950).

KEATS, W., 1990, Uranium, in Geology and mineral resources of Western Australia: Western Australia Geological Survey, Memoir 3, p. 728–731.


KENT, A. J. R., and HAGEMANN, S. G., 1996, Constraints on the timing of lode-gold mineralization in the Wiluna greenstone belt, Yilgarn Craton, Western Australia: Australian Journal of Earth Sciences, v. 443, p. 573–588.

KENT, A. J. R., and McDOUGALL, I., 1995, 40Ar–39Ar and U–Pb age constraints on the timing of gold mineralization in the Kalgoorlie Gold Field, Western Australia: Economic Geology, v. 90, p. 845–859.

KRAPEZ, B., BROWN, S. J. A., HAND, J., BARLEY, M. E., and CAS, R. A. F., 2000, Age constraints on recycled crustal and supracrustal sources of Archaean metasedimentary sequences, Eastern Goldfi elds Province, Western Australia. Evidence from SHRIMP zircon dating: Tectonophysics, v. 322, p. 89–133.

KRIEWALDT, M., 1970, Menzies, W.A.: Western Australia Geological Survey, 1:250 000 Geological Series Explanatory Notes, 11p.

LANGFORD, F. F., 1974, A supergene origin for vein-type uranium ores in the light of the Western Australian calcrete–carnotite deposits: Economic Geology, v. 69, p. 516–526.

LANGFORD, R. L., and FARRELL, T. R., 1998, Geology of the Duketon 1:100 000 sheet: Western Australia Geological Survey, 1:100 000 Geological Series Explanatory Notes, 27p.

LANGFORD, R. L., and LIU, S. F., 1997, Wiluna, W.A. Sheet 2944 (1st edition): Western Australia Geological Survey, 1:100 000 Geological Series.

LANGFORD, R. L., WYCHE, S., and LIU, S. F., 2000, Geology of the Wiluna 1:100 000 sheet: Western Australia Geological Survey, 1:100 000 Geological Series Explanatory Notes, 26p.

LESHER, C. M., and ARNDT, N. T., 1995, REE and Nd isotope geochemistry, petrogenesis and volcanic evolution of contaminated komatiites at Kambalda, Western Australia: Lithos, v. 34, p. 127–157.

LIBBY, J. W., STOCKMAN, P. R., CERVOJ, K. M., MUIR, M. R. K., WHITTLE, M., and LANGWORTHY, P. J., 1998, Perseverancenickel deposit, in Geology of Australian and Papua New Guinean mineral deposits edited by D. A. BERKMAN and D. H.MACKENZIE: The Australasian Institute of Mining and Metallurgy, Monograph 22, p. 321–328.

LIU, S. F., 2000, Sir Samuel, W.A. Sheet SG 51-13 (2nd edition): Canberra, Australian Geological Survey Organisation, 1:250 000 Geological Series.

LIU, S. F., GRIFFIN, T., WYCHE, S., and WESTAWAY, J., 1996, Sir Samuel, W.A. Sheet 3042 (1st edition): Western Australia Geological Survey, 1:100 000 Geological Series.

LIU, S. F., GRIFFIN, T., WYCHE, S., WESTAWAY, J., and FERGUSON, K. M., 1998, Geology of the Sir Samuel 1:100 000 Sheet: Western Australia Geological Survey, 1:100 000 Geological Series Explanatory Notes, 25p.

LORD, J. H., and de la HUNTY, L. E., 1950, Report on the manganese deposit on temporary reserve 1225H near Laverton, W.A.: Western Australia Geological Survey, Annual Report 1948, p. 49.

LYONS, P., STEWART, A. J., JAGODZINSKI, E. A., and CHAMPION, D. C., 1996, Wanggannoo, W.A. Sheet 3143 (preliminary edition): Canberra, Australian Geological Survey Organisation, 1:100 000 Geological Series.

McCLAY, K. R., and CAMPBELL, I. H., 1976, The structure and shape of the Jimberlana Intrusion, Western Australia, as indicated by an investigation of the Bronzite Complex: Geological Magazine, v. 113, p. 129–139.

McGOLDRICK, P. J., 1993, Norseman, W.A. Sheet 3233: Western Australia Geological Survey, 1:100 000 Geological Series.

MANN, A. W., and HORWITZ, R. C., 1979, Groundwater calcrete deposits in Australia: some observations from Western Australia: Journal of the Geological Society of Australia, v. 26, p. 293–303.


38

MARTIN, H., 1994, The Archaean grey gneisses and the genesis of continental crust, in Archaean crustal evolution edited by K. C. CONDIE: Amsterdam, The Netherlands, Elsevier, p. 205–259.

MESSENGER, P. R., 2000, Igneous geochemistry and base metal potential of the Yandal belt, in Yandal greenstone belt: regolith, geology and mineralization edited by G. N. PHILLIPS and R. R. ANAND: Australian Institute of Geoscientists, Bulletin, no. 32, p. 69–71.

MORRIS, P. A., 1994a, Geology of the Mulgabbie 1:100 000 sheet: Western Australia Geological Survey, 1:100 000 Geological Series Explanatory Notes, 18p.

MORRIS, P. A., 1994b, Mulgabbie, W.A. Sheet 3337: Western Australia Geological Survey, 1:100 000 Geological Series.

MORRIS, P. A., 1998, Archaean felsic volcanism in the Eastern Goldfi elds Province, Western Australia: Western Australia Geological Survey, Report 55, 80p.

MORRIS, P. A., and WITT, W. K., 1997, Geochemistry and tectonic setting of two contrasting Archaean felsic volcanic associations in the Eastern Goldfi elds, Western Australia: Precambrian Research, v. 83, p. 83–107.

MYERS, J. S., 1990, Precambrian tectonic evolution of part ofGondwana, southwestern Australia: Geology, v. 18, p. 537–540.

MYERS, J. S., 1995, The generation and assembly of an Archaean supercontinent: evidence from the Yilgarn Craton, Western Australia,in Early Precambrian processes edited by M. P. COWARD and A. C. RIES: London, United Kingdom, The Geological Society,Special Publication, no. 95, p. 143–154.

MYERS, J. S., 1997, Preface: Archaean geology of the Eastern Goldfi elds of Western Australia — a regional overview: Precambrian Research, v. 83, p. 1–10.

MYERS, J. S., and SWAGER, C., 1997, The Yilgarn Craton, in Greenstone belts edited by M. DE WIT and L. D. ASHWAL: Oxford Monographs on Geology and Geophysics, no. 35, p. 640–656.

NELSON, D. R., 1995, Compilation of SHRIMP U–Pb zircon geochronology data, 1994: Western Australia Geological Survey, Record 1995/3, 244p.


NELSON, D. R., 1997a, Evolution of the Archaean granite–greenstone terranes of the Eastern Goldfi elds, Western Australia: SHRIMP U–Pb zircon constraints: Precambrian Research, v. 83, p. 57–81.

NELSON, D. R., 1997b, Compilation of SHRIMP U–Pb zircon geochronology data, 1996: Western Australia Geological Survey, Record 1996/2, 189p.


NELSON, D. R., 1999, Compilation of geochronology data, 1998:Western Australia Geological Survey, Record 1999/2, 222p.

NELSON, D. R., 2000, Compilation of geochronology data, 1999: Western Australia Geological Survey, Record 2000/2, 251p.

NEMCHIN, A. A., and PIDGEON, R. T., 1998, Precise conventional and SHRIMP baddeleyite U–Pb age for the Binneringie dyke, near Narrogin, Western Australia: Australian Journal of Earth Sciences, v. 45, p. 673–675.

OVERSBY, B. S., and VANDERHOR, F., 1995, Yerilla, W.A. Sheet 3239: Canberra, Australian Geological Survey Organisation,1:100 000 Geological Series.

OVERSBY, B. S., WHITAKER, A. J., SEDGMEN, A., and BASTRAKOVA, I. V., 1996a, Weebo, W.A. Sheet 3141 (2nd edition):

Canberra, Australian Geological Survey Organisation, 1:100 000 Geological Series.

OVERSBY, B. S., WILLIAMS, P. R., and DUGGAN, M. B., 1996b, Wildara, W.A. Sheet 3041 (2nd edition): Canberra, Australian Geological Survey Organisation, 1:100 000 Geological Series.

PAINTER, M. G. M., and GROENEWALD, P. B., 2000, Mount Belches, W.A. Sheet 3335: Western Australia Geological Survey, 1:100 000 Geological Series.

PAINTER, M. G. M., and GROENEWALD, P. B., 2001, Geology of the Mount Belches 1:100 000 sheet: Western Australia Geological Survey, 1:100 000 Geological Series Explanatory Notes, 38p.

PAINTER, M. G. M., GROENEWALD, P. B., and McCABE, M., 2003, East Yilgarn Geoscience Database: 1:100 000 geology of the Leonora–Laverton region, Eastern Goldfi elds Granite–Greenstone Terrane: Western Australia Geological Survey, Report 84, 45p.

PASSCHIER, C. W., 1994, Structural geology across a proposed Archaean terrane boundary in the eastern Yilgarn craton, Western Australia: Precambrian Research, v. 68, p. 43–64.

PERRING, C. S., BARLEY, M. E., CASSIDY, K. F., GROVES, D. I., McNAUGHTON, N. J., ROCK, N. M. S., BETTENAY, L. F., GOLDING, S. D., and HALLBERG, J. A., 1989, The association of linear orogenic belts, mantle–crustal magmatism and Archean gold mineralisation in the Eastern Yilgarn Block of Western Australia: Economic Geology, Monograph v. 6, p. 571–585.

PHANG, C., and ANAND, R. R., 2000, Distinguishing transported and residual regolith material, in Yandal greenstone belt: regolith, geology and mineralization edited by G. N. PHILLIPS and R. R. ANAND: Australian Institute of Geoscientists, Bulletin, no. 32, p. 125–133.

PHILLIPS, G. N., and ANAND, R. R., (editors), 2000, Yandal greenstone belt: regolith, geology and mineralization: Australian Institute of Geoscientists, Bulletin, no. 32, 400p.

PIDGEON, R. T., and HALLBERG, J. A., 2000, Age relationships in supracrustal sequences in the northern part of the Murchison Terrane, Archaean Yilgarn Craton, Western Australia: a combined fi eld and zircon U–Pb study: Australian Journal of Earth Sciences, v. 47, p. 153–165.

PIDGEON, R. T., and WILDE, S. A., 1990, The distribution of 3.0 and 2.7 Ga volcanic episodes in the Yilgarn Craton of Western Australia: Precambrian Research, v. 48, p. 309–325.

PIRAJNO, F., and ADAMIDES, N. G., 2000, Iron–manganese oxides and glauconite-bearing rocks of the Earaheedy Group: implications for the base metal potential of the Earaheedy Basin: Western Australia Geological Survey, Annual Review 1999–2000, p. 81–87.

PIRAJNO, F., BAGAS, L., SWAGER, C. P., OCCHIPINTI, S. A., and ADAMIDES, N. G., 1996, A reappraisal of the stratigraphy of the Glengarry Basin, Western Australia: Western Australia Geological Survey, Annual Review 1995–96, p. 81–87.

PIRAJNO, F., JONES, A. J., HOCKING, R. M., and HALILOVIC, J., 2004, Geology and tectonic evolution of Palaeoproterozoic basins of the eastern Capricorn Orogen, Western Australia: Precambrian Research, v. 128, p. 315–342.

PIRAJNO, F., OCCHIPINTI, S. A., and SWAGER, C. P., 1998, The geology and tectonic evolution of the Palaeoproterozoic Bryah, Padbury and Yerrida Basins (formerly Glengarry Basin), Western Australia: Precambrian Research, v. 90, p. 119–140.

PLATT, J. P., ALLCHURCH, P. D., and RUTLAND, R. R., 1978, Archaean tectonics in the Agnew supracrustal belt, Western Australia: Precambrian Research, v. 7, p. 3–30.

PURVIS, A. C., NESBITT, R. W., and HALLBERG, J. A., 1972, The geology of part of the Carr Boyd Rocks Complex and its associated nickel mineralization, Western Australia: Economic Geology, v. 67, p. 1093–1113.


39

RATTENBURY, M. S., JAGODZINSKI, E., DUGGAN, M., CHAMPION, D., and BLAKE, D., 1996, Mount Varden, W.A. Sheet 3341: Canberra, Australian Geological Survey Organisation,1:100 000 Geological Series.

RATTENBURY, M. S., and STEWART, A. J., 2000, Ballard, W.A. Sheet 3039 (2nd edition): Canberra, Australian Geological Survey Organisation, 1:100 000 Geological Series.

RATTENBURY, M. S., and SWAGER, C. P., 1994, Lake Carey, W.A. Sheet 3339: Canberra, Australian Geological Survey Organisation, 1:100 000 Geological Series.

REDMAN, B. A., and KEAYS, R. R., 1985, Archaean basic volcanism in the Eastern Goldfi elds Province, Yilgarn Block, Western Australia: Precambrian Research, v. 30, p. 113–152.

RIGANTI, A., and GROENEWALD, P. B., 2004, East Yilgarn Geoscience Database — updated rock codes: Western Australia Geological Survey, Record 2004/13, 72p.

RIGANTI, A., GROENEWALD, P. B., McCABE, M., 2003, East Yilgarn Geoscience Database — a 1:100 000 reinterpretation of the Eastern Goldfi elds regolith: Western Australia Geological Survey, Record 2003/11, 21p.

ROSS, A. A., BARLEY, M. E., BROWN, S. J. A., McNAUGHTON, N. J., RIDLEY, J. R., and FLETCHER, I. R., 2004, Youngporphyries, old zircons: new constraints on the timing of deformation and gold mineralisation in the Eastern Goldfi elds from SHRIMP U–Pb zircon dating at the Kanowna Belle Gold Mine, WesternAustralia: Precambrian Research, v. 128, p. 105–142.

ROTHERHAM, J. F., 2000, Gold mineralization in the oxide-transition zone — Mt Joel prospect, Yandal greenstone belt, in Yandal Greenstone Belt: regolith, geology and mineralization edited by G. N. PHILLIPS and R. R. ANAND: Australian Institute of Geoscientists, Bulletin, no. 32, p. 273–282.

SIMPSON, E. S., 1952, Minerals of Western Australia, Volume 3: Perth, Western Australia, Government Printer, 714p.

SMITHIES, R. H., 1994a, Geology of the Roe 1:100 000 sheet: Western Australia Geological Survey, 1:100 000 Geological Series Explanatory Notes, 15p.

SMITHIES, R. H., 1994b, Roe, W.A. Sheet 3436: Western Australia Geological Survey, 1:100 000 Geological Series.

SMITHIES, R. H., and WITT, W. K., 1997, Distinct basement terranes identifi ed from granite geochemistry in late Archaean granite–greenstones, Yilgarn Craton, Western Australia: Precambrian Research, v. 83, p. 185–201.

SOFOULIS, J., 1966, Widgiemooltha, W.A.: Western Australia Geological Survey, 1:250 000 Geological Series Explanatory Notes, 26p.

SOLOMON, M., and GROVES, D. I., 1994, The geology and origin of Australia’s mineral deposits: Oxford Monographs in Geology and Geophysics, v. 24, 951p.

STEWART, A. J., 1996a, De La Poer, W.A. Sheet 3443 (preliminary edition): Canberra, Australian Geological Survey Organisation, 1:100 000 Geological Series.

STEWART, A. J. 1996b, Laverton, W.A. Sheet 3340: Canberra, Australian Geological Survey Organisation, 1:100 000 Geological Series.

STEWART, A. J., 1999, Geology of the De La Poer (3443) and Urarey (3343) 1:100 000 sheet areas, Yilgarn Block, Western Australia: Canberra, Australian Geological Survey Organisation, Record 1999/33, 14p.

STEWART, A. J., and BASTRAKOVA, I., 1997, Lake Violet, W.A. Sheet 3044 (1st edition): Canberra, Australian Geological Survey Organisation, 1:100 000 Geological Series.

STEWART, A. J., and LIU, S. F., 1997, Leonora, W.A. Sheet 3140 (1st edition): Canberra, Australian Geological Survey Organisation, 1:100 000 Geological Series.


STEWART, A. J., WILLIAMS, I. R., and ELIAS, M., 1983, Youanmi, W.A.: Australia BMR, 1:250 000 Geological Series Explanatory Notes, 58p.

SWAGER, C. P., 1989a, Dunnsville, W.A. Sheet 3036: Western Australia Geological Survey, 1:100 000 Geological Series.

SWAGER, C. P., 1989b, Structure of the Kalgoorlie greenstones —regional deformation history and implications for the structuralsetting of gold deposits within the Golden Mile: Western AustraliaGeological Survey, Report 25, Professional Papers, p. 59–84.

SWAGER, C. P., 1993, Kurnalpi, W.A. Sheet 3336: Western Australia Geological Survey, 1:100 000 Geological Series.

SWAGER, C. P., 1994a, Geology of the Dunnsville 1:100 000 sheet: Western Australia Geological Survey, 1:100 000 Geological Series Explanatory Notes, 22p.

SWAGER, C. P., 1994b, Geology of the Kurnalpi 1:100 000 sheet: Western Australia Geological Survey, 1:100 000 Geological Series Explanatory Notes, 19p.

SWAGER, C. P., 1994c, Geology of the Menzies 1:100 000 sheet (and adjacent Ghost Rocks area): Western Australia Geological Survey, 1:100 000 Geological Series Explanatory Notes, 31p.

SWAGER, C. P., 1994d, Geology of the Pinjin 1:100 000 sheet: Western Australia Geological Survey, 1:100 000 Geological Series Explanatory Notes, 22p.

SWAGER, C. P., 1994e, Pinjin, W.A. Sheet 3437: Western Australia Geological Survey, 1:100 000 Geological Series.

SWAGER, C. P., 1994f, Yabboo, W.A. Sheet 3438: Western Australia Geological Survey, 1:100 000 Geological Series.

SWAGER, C. P., 1995a, Geology of the greenstone terranes in the Kurnalpi–Edjudina region, southeastern Yilgarn Craton: Western Australia Geological Survey, Report 47, 31p.

SWAGER, C. P., 1995b, Geology of the Edjudina and Yabboo 1:100 000 sheets: Western Australia Geological Survey, 1:100 000 Geological Series Explanatory Notes, 35p.

SWAGER, C. P., 1997, Tectono-stratigraphy of late Archaean greenstone terranes in the southern Eastern Goldfi elds, Western Australia: Precambrian Research, v. 83, p. 11–42.

SWAGER, C. P., GOLEBY, B. R., DRUMMOND, B. J., RATTENBURY, M. S., and WILLIAMS, P. R., 1997, Crustal structure of the granite–greenstone terranes in the Eastern Goldfi elds, Yilgarn Craton, as revealed by seismic refl ection profi ling: Precambrian Research, v. 83, p. 43–56.

SWAGER, C. P., and GRIFFIN, T. J., 1990, An early thrust duplex in the Kalgoorlie–Kambalda greenstone belt, Eastern Goldfi elds Province, Western Australia: Precambrian Research, v. 48, p. 63–73.

SWAGER, C. P., GRIFFIN, T. J., WITT, W. K., WYCHE, S., AHMAT, A. L., HUNTER, W. M., and McGOLDRICK, P. J., 1990, Geology of the Archaean Kalgoorlie Terrane — an explanatory note: Western Australia Geological Survey, Record 1990/12, 54p.

SWAGER, C. P., GRIFFIN, T. J., WITT, W. K., WYCHE, S., AHMAT, A. L., HUNTER, W. M., and McGOLDRICK, P. J., 1995, Geology of the Archaean Kalgoorlie Terrane — an explanatory note: Western Australia Geological Survey, Report 48, 26p.

SWAGER, C. P., and NELSON, D. R., 1997, Extensional emplacement of a high-grade granite gneiss complex into low-grade granite greenstones, Eastern Goldfi elds, Western Australia: Precambrian Research, v. 83, p. 203–209.

SWAGER, C. P., and RATTENBURY, M. S., 1994, Edjudina, W.A. Sheet 3338: Western Australia Geological Survey, 1:100 000 Geological Series.

SWAGER, C. P., and WITT, W. K., 1990, Menzies, W.A. Sheet 3138: Western Australia Geological Survey, 1:100 000 Geological Series.


40

TOMICH, S. A., 1956, A report on a manganese deposit on M.L. 22T in temporary reserve 1225H near Laverton, W.A.: Western Australia Geological Survey, Annual Report 1953, p. 16–18.

TYLER, I. M., and HOCKING, R. M., 2001, Tectonic units of Western Australia (scale 1:2 500 000): Western Australia Geological Survey.

TYLER, I. M., and HOCKING, R. M., 2002, A revision of the tectonic units of Western Australia: Western Australia Geological Survey, Annual Review 2000–01, p. 33–44.

TYLER, I. M., MORRIS, P. A., THORNE, A. M., SHEPPARD, S., SMITHIES, R. H., RIGANTI, A., DOYLE, M. G., and HOCKING, R. M., in prep., The revised GSWA rock classifi cation scheme: Western Australia Geological Survey, Annual Review 2003–04.

van de GRAAFF, W. J. E., CROWE, R. W. A., BUNTING, J. A., and JACKSON, M. J., 1977, Relict early Cainozoic drainages in arid Western Australia: Zeitschrift fur Geomorphologie, v. 21, p. 379–400.

WEINBERG, R. F., MORESI, L., and VAN DER BORGH, P., 2003. Timing of deformation in the Norseman–Wiluna Belt, Yilgarn Craton, Western Australia: Precambrian Research, v. 120, p. 219–239.

WESTAWAY, J. M., and WYCHE, S., 1998, Geology of the Darlot 1:100 000 sheet: Western Australia Geological Survey, 1:100 000 Geological Series Explanatory Notes, 24p.

WHITAKER, A. J., 2002, Aeromagnetic interpretation of the Yilgarn Craton with an emphasis on the north eastern Yilgarn, in Geology, geochronology and geophysics of the north eastern Yilgarn Craton, with an emphasis on the Leonora–Laverton transect area edited by K. F. CASSIDY: Canberra, Geoscience Australia, Record 2002/18, p. 1–6.

WHITAKER, A. J., and BASTRAKOVA, I. V., 2002, The Yilgarn Craton aeromagnetic interpretation (1:1 500 000 scale map) SG 50 – SI 51: Canberra, Geoscience Australia.

WHITAKER, A. J., BLAKE, D. H., and STEWART, A. J., 2000, Geology and geophysics of the Ballimore and Sandalwood 1:100 000 sheet areas (3145 and 3144), Western Australia: Canberra, Australian Geological Survey Organisation, Record 2000/2, 20p.

WILLIAMS, D. A. C., and HALLBERG, J. A., 1973, Archaean layered intrusions of the Eastern Goldfi elds region, Western Australia: Contributions to Mineralogy and Petrology, v. 38, p. 45–70.

WILLIAMS, I. R., 1970, Kurnalpi, W.A.: Western Australia Geological Survey, 1:250 000 Geological Series Explanatory Notes, 37p.

WILLIAMS, I. R., GOWER, C. F., and THOM, R., 1976, Edjudina, W.A.: Western Australia Geological Survey, 1: 250 000 Geological Series Explanatory Notes, 32p.

WILLIAMS, P. R., 1993, A new hypothesis for the evolution of the Eastern Goldfi elds Province, in Kalgoorlie 93 — An international conference on crustal evolution, metallogeny, and exploration in the Eastern Goldfields edited by J. A. WILLIAMS and J. A. HALDANE: Canberra, Australian Geological Survey Organisation, Record 1993/54, p. 77–84.

WILLIAMS, P. R., 1998, Geology, structure, and gold resources of the Leonora 1:100 000 sheet, W.A.: Canberra, Australian Geological Survey Organisation, Record 1998/9, 71p.

WILLIAMS, P. R., DUGGAN, M. B., CURRIE, K. L., BASTRAKOVA, I. V., 1995, Minerie, W.A. Sheet 3240 (preliminary edition): Canberra, Australian Geological Survey Organisation, 1:100 000 Geological Series.

WINGATE, M. T. D., CAMPBELL, I. H., and HARRIS, L. B., 2000, SHRIMP baddeleyite age for the Fraser Dyke Swarm, southeast Yilgarn Craton, Western Australia: Australian Journal of EarthSciences, v. 47, p. 309–313.

WITT, W., 1990, Melita, W.A. Sheet 3139: Western Australia Geological Survey, 1:100 000 Geological Series.

WITT, W. K., 1992, Porphyry intrusions and albitites in the Bardoc–Kalgoorlie area, Western Australia, and their role in Archaean epigenetic gold mineralisation: Canadian Journal of Earth Sciences, v. 29, p. 1609–1622.

WITT, W. K., 1994a, Geology of the Bardoc 1:100 000 sheet: Western Australia Geological Survey, 1:100 000 Geological Series Explanatory Notes, 50p.

WITT, W. K., 1994b, Geology of the Melita 1:100 000 sheet: Western Australia Geological Survey, 1:100 000 Geological SeriesExplanatory Notes, 63p.

WITT, W. K., 1995, Tholeiitic and high-Mg mafi c–ultramafi c sills in the Eastern Goldfi elds Province, Western Australia: implications for tectonic settings: Australian Journal of Earth Sciences, v. 42, p. 407–422.

WITT, W. K., and DAVY, R., 1997, Geology and geochemistry of Archaean granites in the Kalgoorlie region of the Eastern Goldfi elds, Western Australia: a syncollisional tectonic setting?: Precambrian Research, v. 83, p. 133–183.

WITT, W. K., DAVY, R., and CHAPMAN, D., 1991, The Mount Pleasant sill, Eastern Goldfi elds, Western Australia: iron-rich granophyre in a layered high-Mg intrusion: Western Australia Geological Survey, Report 30, p. 73–92.

WITT, W. K., and SWAGER, C. P., 1989a, Bardoc, W.A. Sheet 3137: Western Australia Geological Survey, 1:100 000 Geological Series.

WITT, W. K., and SWAGER, C. P., 1989b, Structural setting and geochemistry of Archaean I-type granites in the Bardoc–Coolgardie area of the Norseman–Wiluna belt, Western Australia: Precambrian Research, v. 44, p. 323–351.

WITT, W. K., SWAGER, C. P., and NELSON, D. R., 1996, 40Ar/39Ar and U–Pb constraints on the timing of gold mineralization in the Kalgoorlie gold fi eld, Western Australia — a discussion: Economic Geology, v. 91, p. 792–795.

WITT, W. K., and VANDERHOR, F., 1998, Diversity within a unifi ed model for Archaean gold mineralization in the Yilgarn Craton of Western Australia: an overview of the late-orogenic, structurally-controlled gold deposits: Ore Geology Reviews, v. 13, p. 29–64.

WOODHEAD, J. D., and HERGT, J. M., 1997, Application of the ‘double spike’ technique to Pb-isotope geochronology: Chemical Geology, v. 138(3–4), p. 311–321.

WYBORN, L. A. I., 1993, Constraints on interpretations of lower crustal structure, tectonic setting and metallogeny of the Eastern Goldfi elds and Southern Cross Provinces provided by granite geochemistry: Ore Geology Reviews, v. 8, p. 125–140.

WYCHE, S., 1995, Mulline, W.A. Sheet 2938: Western Australia Geological Survey, 1:100 000 Geological Series.

WYCHE, S., 1998, Kalgoorlie, W.A. Sheet 3136: Western Australia Geological Survey, 1:250 000 Geological Series Explanatory Notes, 31p.

WYCHE, S., 1999, Geology of the Mulline and Riverina 1:100 000 sheets: Western Australia Geological Survey, 1:100 000 Geological Series Explanatory Notes, 28p.

WYCHE, S., 2003, Mount Mason, W.A. Sheet 2939 (1st edition): Western Australia Geological Survey, 1:100 000 Geological Series.

WYCHE, S., CHEN, S. F., GREENFIELD, J. E., and RIGANTI, A., 2001, Geology and tectonic evolution of the Central Yilgarn Craton, Western Australia, in 4th International Archaean Symposium 2001, Extended Abstracts edited by K. F. CASSIDY, J. M. DUNPHY, and M. J. VAN KRANENDONK: Canberra, AGSO – Geoscience Australia, Record 2001/37, p. 109–111.

WYCHE, S., and GRIFFIN, T., 1998, Depot Springs, W.A. Sheet 2842 (1st edition): Western Australia Geological Survey, 1:100 000 Geological Series.


WYCHE, S., HUNTER, W. M., and WITT, W. K., 1992, Davyhurst, W.A. Sheet 3037: Western Australia Geological Survey, 1:100 000 Geological Series.

WYCHE, S., NELSON, D. R., and RIGANTI, A., 2004, 4350–3130 Ma detrital zircons in the Southern Cross Granite–Greenstone Terrane, Western Australia: implications for the early evolution of the Yilgarn Craton: Precambrian Research, v. 51, p. 31–45.

WYCHE, S., and SWAGER, C. P., 1995, Riverina, W.A. Sheet 3038: Western Australia Geological Survey, 1:100 000 Geological Series.

WYCHE, S., and WESTAWAY, J. M., 1996, Darlot, W.A. Sheet 3142: Western Australia Geological Survey, 1:100 000 Geological Series.

WYCHE, S., and WITT, W. K., 1994, Geology of the Davyhurst1:100 000 sheet: Western Australia Geological Survey, 1:100 000 Geological Series Explanatory Notes, 21p.

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YEATS, C. J., GROVES, D. I., McNAUGHTON, N. J., DUNPHY,J. M., KOHLER, E., GEBRE-MARIAM, M., and VIELREICHER, N. M., 2000, Constraints on the age of gold mineralization in theYandal belt, in Yandal greenstone belt: regolith, geology and mineralization edited by G. N. PHILLIPS and R. R. ANAND: Australian Institute of Geoscientists, Bulletin, no. 32, p. 215–217.

YEATS, C. J., and McNAUGHTON, N. J., 1997, Signifi cance of SHRIMP II U–Pb geochronology on lode-gold deposits of the Yilgarn Craton, in Kalgoorlie '97 — an international conference on crustal evolution, metallogeny and exploration of the Yilgarn Craton — an update, extended abstracts compiled by K. F. CASSIDY, A. J. WHITAKER, and S. F. LIU: Canberra, Australian Geological Survey Organisation, Record 1997/41, p. 125–130.

1


Appendix 1

Standardized regolith and bedrock codes of the East Yilgarn 1:100 000 Geological Information Series database

RationaleSymbols identifying regolith and bedrock map units on standard Geological Survey of Western Australia (GSWA) geological series maps (either plotted or in PDF format) convey information through the use of upper and lower case letters, small capitals, subscripts, hyphens, and italics.

These symbols cannot be entered in the look-up table for the surface geology dataset for the 1:100 000 Geological Information Series, and cannot be displayed on-screen. The map unit codes provided in the look-up table are in a format that ensures a unique code for each map unit, which can be interpreted to extract the same information that is inherent in the format of the unit symbol on maps.

The construction of regolith map unit symbols is set out in Hocking et al. (2001). In printed maps, regolith symbols are in italics to distinguish them from bedrock symbols, but for entry into the surface geology look-up table the regolith code is preceded by an underscore. The code consists of three parts: Landform, regolith composition, and parent rock or cement type. Each part is separated by a hyphen. Where there are two letters the second is subscripted in the map unit symbol.

Bedrock map unit symbols and codes can consist of up to four parts, following the same order (from left to right) as the information presented on a standard map reference: geological time, stratigraphic unit, lithology, and tectonic unit. In general no more than three parts are required to uniquely code a map unit. In bedrock map unit symbols a hyphen is placed between the stratigraphic unit and the lithology part of the symbol only. In the surface geology look-up table all the different parts of the code are separated by hyphens.

The geological time component follows traditional system notation, with some variations to accommodate GSWA usage (Proterozoic is represented by P_). Map unit codes for stratigraphic units presently consist of one or two capital letters for each group or equivalent, followed by one or two lower case letters for a formation or equivalent. A single, lower case letter may follow this for a named member. Where a formation is not assigned to a group, an underscore acts as a ‘place holder’ for the Group letter(s) in the bedrock code.

Codes for lithology follow the GSWA rock classifi -cation scheme (Tyler et al., in prep.). A two or three capital letter code for each tectonic unit is taken from the Tectonic units of Western Australia map of Tyler and Hocking (2001).

42

Regolith codes

Depositional units

Alluvial units

_A Clay, silt, sand, and gravel in channels and on fl oodplains

_Ad Clay, silt, and sand in braided swales on fl oodplains

_Af Clay, silt, and sand on fl oodplains

_Ap Clay and silt in claypans

_A-k Calcrete and carbonate-cemented alluvium in fl uvial channels

_Av-q-s Semiconsolidated, ferruginous quartz sandstone in alluvial fans

_A2 Moderately to strongly indurated sand with locally abundant pebbles, and minor silt and clay, restricted to old valley systems

_A2-q-z Medium- to coarse-grained sandstone; detrital quartz grains cemented by ferruginous chalcedony; local bedding and grading

Colluvial units

_C Colluvium derived from different rock types; includes gravel, sand, and silt

_C-f Ferruginous gravel and reworked ferruginous duricrust

_C-g Quartzofeldspathic gravel, sand, and silt, commonly derived from granitic rock and associated weathering products

_C-k Colluvium dominated by calcrete; includes loose nodules and irregular fragments

_C-l-ci Talus derived from banded-iron formation and chert; locally cemented

_C-q Quartz-vein debris

_C-z-u Colluvium derived from siliceous caprock over ultramafi c rock

Lacustrine units_Ld Sand, silt, and gypsum in dunes adjacent

to and within playa lakes

_Ld1 Dune and lake deposits; active systems within and adjacent to playa lakes; non-vegetated or poorly vegetated

_Ld2 Stabilized dunes within and adjacent to playa lakes; typically vegetated


4

_Ld-eg Lithifi ed gypsum and clay, in mounds and dunes adjacent to playa lakes

_Lf Freshwater lakes, commonly surrounded by swamps

_Lg Silt, sand, and gravel in halophyte fl ats adjacent to playas

_Lm Mixed dunes, evaporite, and alluvial deposits, typically adjacent to playa lakes

_Lp Saline and gypsiferous evaporite deposits, clay, silt, and sand in playa lakes

_Lw Clay and silt in swamps, commonly surrounding clay ponds and lagoons

_L-c Clay and silt in localized depressions

_L-k Calcrete within playa lake systems

Sandplain units

_S Residual and eolian sand with minor silt and clay; low, vegetated dunes locally common

_Sd Sand in stabilized dunes, common at claypan margins

_Sp Sand and playa terrain; dunes dominant

_S-l Yellow sand with minor pisolitic laterite, ferruginized silcrete, silt, and clay; common on low plateaus associated with weathered granitic rock

Sheetwash unit

_W Clay, silt, and sand in extensive fans; local ferruginous gravel

_W-c Clay-rich sheetwash deposits

_W-f Clay, silt, and sand with abundant ferruginous grit

_W-g Clay, silt, and sand commonly derived from granitic rock

_W-q Clay, silt, and sand with abundant quartz-vein debris

Residual or relict units_R-d Undivided residual or relict material;

mainly ferruginous and siliceous duri-crust; minor calcrete and kaolinized rock

_R-d-pg Silcrete and/or kaolinized granitic rock

_R-f Ferruginous duricrust, massive to rubbly; includes iron-cemented reworked products

_R-f-i Ferruginous duricrust as massive ironstone forming ridges and cappings

_R-g Quartzofeldspathic sand, commonly over granitic rock

_R-g-pg Quartzofeldspathic sand and minor silcrete over granite; sparse granite outcrop;

3

includes mottled and leached zones of weathering profi le

_R-k Calcrete of residual origin; includes reworked carbonate products

_R-km-u Magnesite, derived from ultramafi c rock

_R-m-p Residual, deep red, unconsolidated soil overlying Proterozoic mafi c and ultramafi c rock

_R-z Silcrete

_R-z-i Ferruginous silcrete

_R-z-u Silica caprock over ultramafi c rock; local chalcedony and chrysoprase

Exposed unit_Xw Deeply weathered rock; protolith

undetermined

Rock codes

Cainozoic rocks — Eucla Basin, Eundynie GroupEe-E-s EUNDYNIE GROUP, undivided; domin-

antly sandstone; includes conglomerate, siltstone, mudstone, spongolitic or bituminous siltstone, calcareous sandstone, and bioclastic calcarenite; generally poorly indurated; locally silicified and with common ferruginized cappings

Ee-E-kl EUNDYNIE GROUP: limestone, massive to weakly bedded; locally fossiliferous with gastropod, brachiopod, and bivalve fossils

Ee-Ep-st EUNDYNIE GROUP, PALLINUP FORMATION: sandstone, quartz-rich and poorly sorted, with spongolitic and calcareous varieties; includes subordinate gravel, conglomerate, and siltstone

Permian rocks — Gunbarrel BasinP-_a-sgpg PATERSON FORMATION: conglom-

erate with sandstone and siltstone; generally of glacigene origin

P-_a-sl PATERSON FORMATION: shale and siltstone; probably of lacustrine origin

P-_a-ss PATERSON FORMATION: sandstone, with pebbly to bouldery siltstone, conglomerate, and mudstone; probably of fl uviatile origin

P-sc Unassigned conglomerate; polymictic, poorly sorted; fl uvioglacial deposit

P-sl Unassigned shale and siltstone


44

Proterozoic sedimentary rocksP_-_k-scp KALUWEERIE CONGLOMERATE:

polymictic conglomerate

P_-_k-ssa KALUWEERIE CONGLOMERATE: arkosic sandstone and mudstone

P_-s Unassigned conglomerate, quartz-rich sandstone, arkosic sandstone, and microbial laminates; commonly silicifi ed and brecciated

Proterozoic rocks — Earaheedy Basin, Earaheedy GroupP_-EAck-sl CHIALL FORMATION, Karri Karri

Member: shaly siltstone

P_-EAcw-ss CHIALL FORMATION, Wandiwarra Member: sandstone and shale

P_-EAf-ci FRERE FORMATION: peloidal chert, granular iron-formation, granular siliceous iron-formation, siltstone, and sandstone

P_-EAf-cig FRERE FORMATION: granular iron-formation and peloidal chert; minor siltstone and shale

P_-EAf-sl FRERE FORMATION: shaly siltstone; minor chert and fi ne-grained sandstone

P_-EAfd-kl FRERE FORMATION, Windidda Member: limestone and shale

P_-EAy-s YELMA FORMATION: sandstone, arkose, shale, siltstone, conglomerate, and stromatolitic dolomite; minor chert breccia

P_-EAy-k YELMA FORMATION: locally stromat-olitic carbonate rock, and shale

P_-EAy-st YELMA FORMATION: fi ne- to medium-grained sandstone with pebble lags towards base

Proterozoic rocks — Yerrida Basin, Yerrida Group

Mooloogool Subgroup

P_-YMk-bb KILLARA FORMATION: tholeiitic basalt; locally amygdaloidal; minor nontronite layers

P_-YMk-od KILLARA FORMATION: dolerite and gabbro, mainly in sills; minor disseminated sulfi des (hypabyssal equivalent of Killara Formation basalt)

P_-YMkb-cc KILLARA FORMATION, Bartle Member: chert, chert breccia, laminated chert, and silicifi ed sedimentary rock; locally with pseudomorphs of anhydrite crystals and nodules; minor basalt

Windplain SubgroupP_-YWj-s JUDERINA FORMATION: quartz

sandstone; local sandstone, chert breccia, and conglomerate

P_-YWjb-c JUDERINA FORMATION, Bubble Well Member: laminated stromatolitic chert, stromatolitic carbonate beds, and dolostone

P_-YWjf-sa JUDERINA FORMATION, Finlayson Member: quartz arenite; planar bedded or cross-bedded; minor pebble conglomerate and intercalated siltstone

P_-YWj-sl JUDERINA FORMATION: shale and siltstone

Proterozoic felsic dykesP_-gi Diorite dyke

Proterozoic mafi c–ultramafi c dykesP_-od Mafic and ultramafic dykes; mainly

dolerite and gabbro; includes cumulate and granophyric differentiates

Yilgarn Craton

Proterozoic mafi c–ultramafi c dykes — named

P_-Wb-o BINNERINGIE DYKE: mainly dolerite and gabbro; includes cumulate and granophyric differentiates; part of the Widgiemooltha Dyke Suite

P_-Wc-o CELEBRATION DYKE: mainly dolerite and gabbro; includes cumulate and granophyric differentiates; part of the Widgiemooltha Dyke Suite

P_-Wi-o PINJIN DYKE: mainly dolerite and gabbro; includes cumulate and granophyric differentiates; part of the Widgiemooltha Dyke Suite

P_-Wj-ax JIMBERLANA DYKE: pyroxenite; part of the Widgiemooltha Dyke Suite

P_-Wj-ow JIMBERLANA DYKE: norite; part of the Widgiemooltha Dyke Suite

P_-Wk-o KALPINI DYKE: mainly dolerite and gabbro; includes cumulate and granophyric differentiates; part of the Widgiemooltha Dyke Suite

P_-Wl-o BALLONA DYKE: mainly dolerite and gabbro; includes cumulate and granophyric differentiates; part of the Widgiemooltha Dyke Suite

P_-Wr-o RANDALLS DYKE: mainly dolerite and gabbro; includes cumulate and grano-phyric differentiates; part of the Widgiemooltha Dyke Suite


45

Dykes and veins, unassigned age

zd Epidosite

zq Quartz vein or pod; massive, crystalline, or brecciated

zqi Goethite–quartz and quartz–goethite veins

zqix Goethite/hematite–quartz breccia

g Granitic dyke

gg Granodiorite dyke

gi Diorite dyke

gna Microgranite dyke

gp Pegmatite dyke or pod

gt Tonalite dyke

gv Granophyric dyke

od Dolerite dyke or sill

y Lamprophyre dyke

Archaean metamorphic rocks — protolith unknown

A-mehd Quartz–chloritoid–aluminosilicate rock; with andalusite and/or kyanite; within felsic volcanic and volcaniclastic rock

A-mehk Quartz–chloritoid–kyanite rock

A-memu Quartz–fuchsite or andalusite–quartz–fuchsite rock; laminated, complexly veined, or massive; local chert or quartz–mica schist interlayers

A-meq Quartzitic granofels; typically local unit within felsic gneisses

A-mex Pyroxene hornfels

A-mna Amphibolitic gneiss; commonly foliated and/or lineated; local clinopyroxene(–garnet)-bearing calc-alkaline gneiss

A-mnkq Calc-silicate gneiss (subsurface only)

A-mnw Gneiss and minor schist after undetermined mafic protolith; locally migmatitic; subordinate felsic component

A-msa Amphibolite, schistose; clinopyroxene, cummingtonite, and/or garnet present locally; protolith unknown

A-xmsa-mfs Amphibolite and/or amphibolitic schist, with subordinate garnet-bearing porphyr-itic rock, microgranitic dykes, schistose felsic volcanic rocks, and/or quartz–feldspar–amphibole schist

A-msab Hornblende–biotite schist (subsurface only)

A-msb Biotite schist (subsurface only)

A-msc Chlorite schist

A-msd Quartz–aluminosilicate rock within felsic volcanic sequences; commonly schistose; abundant andalusite poikiloblasts; local minor kyanite or chloritoid


A-msj Ferruginous schist

A-msjg Gruneri te–hornblende–magnet i te–plagioclase rock; moderately to weakly foliated

A-msk Quartz–kyanite schist; andalusite and/or chloritoid present locally

A-msmq Muscovite–quartz schist

A-msmu Fuchsite–quartz(–andalusite) schist with interlayered quartz–feldspar–muscovite schist and minor tremolite schist

A-mspy Phyllonite and mylonite, exposed in fault or shear zones; locally carbonaceous

A-msqb Quartz–biotite(–feldspar–muscovite) schist

A-msqc Quartz–chlorite schist; chlorite–magnetite–feldspar schist, and chlorite schist; locally deeply weathered

A-msqf Quartz–feldspar(–muscovite) schist; locally deeply weathered

A-msqk Quartz–feldspar schist containing kyanite

A-msqm Quartz–muscovite(–feldspar) schist

A-msrc Chlorite–albite–actinolite schist

A-xmsw-msu Amphibolitic and chloritic schist; commonly wea thered ; p ro to l i th unknown

Archaean metasomatic rocks

A-mzk Massive carbonate rock; recrystallized

A-mzr Greisen

Archaean felsic meta-igneous rocks

A-mrn Banded to agmatitic felsic gneiss; minor calc-silicate and mafi c components

A-mrzf Felsic, albite-rich, quartz-poor porphyr-itic rock; variably foliated

Archaean mafi c meta-igneous rocks

A-mw Metamorphosed mafi c igneous rock

A-mwa Amphibolite; relict, coarse plagioclase phenocrysts

Archaean granitic rocks

A-xmg-mnf Quartz-rich granitic rock and quartzo-feldspathic gneiss

A-xmg-ms Metamorphosed porphyritic dykes and sills, granitic to granodioritic in composition, interleaved with poorly exposed quartz–chlorite schist

A-mge Hornfelsed granitic rock


46

A-xmgg-mb Metamorphosed granodiorite to monzo-granite interleaved with granitic schist and diverse greenstone lithologies on all scales

A-mgln Gneissic leucocratic granitic rock; locally quartzitic

A-mgms Foliated biotite monzogranite, medium to coarse grained; minor granodiorite and pegmatite dykes

A-mggu Granodiorite and tonalite gneiss with streaky augen of quartz and granular feldspar

A-mgn Quartzofeldspathic granitic gneiss; locally migmatitic; includes local mafi c bands and enclaves

A-xmgn-mba Quartzofeldspathic gneiss interleaved with amphibolite and metamorphosed mafi c rock

A-mgrn K-feldspar–quartz gneiss

A-mgsn Foliated and gneissic granitic rock; moderately to strongly foliated granite with local gneissic component

A-mgss Foliated granitic rock; locally gneissic; includes amphibolite lenses

A-xmgss-mba Foliated granitic rock interleaved with subordinate amphibolite and foliated mafic rock; gneissic banding locally developed

A-mgws Foliated syenite

A-g Granitic rock, undivided; includes deeply weathered rock

A-gc Quartz monzonite; commonly porphyritic

A-gd Quartz diorite and quartz monzodiorite

A-ge Quartz syenite

A-gei Quartz syenite to quartz monzonite; hornblende-bearing, minor clinopyroxene locally; numerous mafi c enclaves

A-gf Alkali-feldspar granite

A-gg Granodiorite; monzogranite, diorite, and microgranitic enclaves locally

A-ggp Porphyritic granodiorite (subsurface only)

A-ghp Porphyritic monzodiorite; plagioclase phenocrysts, K-feldspar megacrysts; locally quartz phyric

A-gi Diorite to quartz monzodiorite; with hornblende, clinopyroxene, and/or biotite; in small dykes and stocks

A-gip Porphyritic diorite or microdiorite

A-gkp Quartz monzodiorite, porphyritic; zoned plagioclase phenocrysts

A-gm Monzogranite; biotite bearing, local hornblende; commonly medium to coarse grained; minor granodiorite

A-gma Fine-grained biotite monzogranite

A-gmd Very coarse grained biotite monzogranite

A-gmh Hornblende–biotite monzogranite; alkali-feldspar megacrysts present locally

A-gmm Medium-grained biotite monzogranite

A-gmp Porphyritic monzogranite

A-gmq Quartz-rich monzogranite

A-gna Fine-grained granitic rock

A-gnd Very coarse grained granitic rock

A-gnl Leucocratic granitic and microgranitic rocks

A-gnme Medium-grained, equigranular granitic rock

A-gnp Porphyritic granitic rock, undivided; includes dykes and sills

A-gnph Hornblende-bearing, porphyritic, felsic rocks; plagioclase phenocrysts; as dykes; locally schistose

A-gnpq Quartz–feldspar porphyritic rock, as dykes

A-gnq Quartz-rich granitic rock

A-gr Syenogranite

A-gra Syenogranite to alkali-feldspar granite, very fi ne grained, equigranular

A-gt Tonalite

A-gtp Porphyritic tonalite

A-gv Granophyre; quartz, plagioclase, and hornblende bearing; coarse grained

A-gy Syenite to alkali-feldspar syenite; locally porphyritic

A-gyi Syenite to quartz syenite; numerous mafi c schlieren and xenoliths

A-gz Monzonite

Archaean granitic rocks — named

A-_ad-gr FAIR ADELAIDE SYENOGRANITE: medium-grained, equigranular, massive syenogranite; contacts discordant with greenstones and early foliation in granitic rock

A-_bd-gg BULDANIA GRANODIORITE: composite intrusion; predominantly seriate biotite–hornblende granodiorite

A-_bl-gm BALI MONZOGRANITE: coarse-grained monzogranite with K-feldspar megacrysts; internally massive, intense contact-parallel foliation with down-dip mineral lineation

A-_bo-gm BORA MONZOGRANITE: medium-grained, equigranular biotite monzo-granite; scattered mafic enclaves and strong foliation

A-_br-gm BURRA MONZOGRANITE: coarse-grained biotite monzogranite; K-feldspar megacrysts; generally homogeneous, deformed at margins; possibly composite intrusion


A-_bu-gm BULLA ROCKS MONZOGRANITE: fi ne- to coarse-grained biotite monzo-granite; K-feldspar phenocrysts, locally megacrystic; foliated

A-_by-gm BULYAIRDIE MONZOGRANITE: medium-grained, hornblende monzo-granite; perthitic K-feldspar megacrysts

A-_ca-gm CAWSE MONZOGRANITE: coarse-grained biotite monzogranite, equigranular to porphyritic, locally seriate; domal in D2 anticlines; moderate to weak foliation; sheared contacts

A-_cb-gg CROWBAR GRANODIORITE: medium- to coarse-grained, equigranular grano-diorite; domal within regional anticline; pervasive foliation

A-_cf-gm COPPERFIELD MONZOGRANITE: biotite monzogranite with prominent mineral lineation

A-_cl-gm CALOOLI MONZOGRANITE: medium- to coarse-grained, equigranular biotite monzogranite; generally massive, foliated near margins

A-_co-gm COWARNA MONZOGRANITE: medium-grained, leucocratic, biotite-bearing monzogranite; K-feldspar phenocrysts

A-_cr-gg CREDO GRANODIORITE: medium-grained biotite granodiorite; domal within regional anticline; foliation strongest near margins

A-_cs-gr CARPET SNAKE SYENOGRANITE: massive muscovite–biotite syenogranite; pegmatitic segregations

A-_cv-gm COMET VALE MONZOGRANITE: fi ne to medium grained, porphyritic monzo-granite; local foliation; discordant contacts with greenstones

A-_cw-gm CLARK WELL MONZOGRANITE: seriate, biotite-bearing monzogranite

A-_dd-gg DOYLE DAM GRANODIORITE: post-D2 to syn-D3, K-feldspar-phyric grano-diorite; massive to weakly foliated; discordant to greenstones

A-_de-gg DEPOT GRANODIORITE: medium- to coarse-grained, hornblende leuco-granodiorite–leucotonalite; foliation moderate except in numerous shear zones; intrusive western contact

A-_dn-gg DUNNSVILLE GRANODIORITE: medium- to coarse-grained granodiorite; penetrative foliation and subhorizontal mineral lineation; sheared contacts with greenstones have subhorizontal to steep mineral lineation

A-_fi -mgn FIFTY MILE TANK GNEISS: quartzo-feldspathic gneiss, porphyroclastic; minor monzogranite; schistose mafi c to ultramafi c enclaves common

47


A-_fi -mgnp FIFTY MILE TANK GNEISS: quartzo-feldspathic gneiss, with numerous deformed pegmatite veins

A-_ga-gm GALVALLEY MONZOGRANITE: biotite monzogranite with prominent K-feldspar megacrysts; aligned K-feldspar, biotite, and xenoliths define foliation locally

A-_gd-gm GOAT DAM MONZOGRANITE: equi-granular biotite monzogranite; strongly deformed mafi c enclaves locally

A-_gi-gm GOODIA MONZOGRANITE: fi ne- to medium-grained, equigranular biotite monzogranite to granodiorite; strongly foliated margins

A-_gl-gm GALAH MONZOGRANITE: muscovite–biotite monzogranite; numerous pegmat-itic segregations

A-_go-gm GOONGARRIE MONZOGRANITE: biotite-bearing monzogranite with local prominent K-feldspar megacrysts; domal within D2 anticline; weak to moderate foliation; deformed contacts

A-_jo-gm JORGENSON MONZOGRANITE: equigranular monzogranite; strongly sheared marginal areas

A-_ju-gm JUNGLE MONZOGRANITE: biotite monzogranite

A-_ka-gm KARRAMINDIE MONZOGRANITE: fine- to medium-grained biot i te monzogranite

A-_kk-gm KIAKI MONZOGRANITE: leuco-monzogranite, typically deeply weathered; intrudes and hornfelses rocks of the MOUNT BELCHES FORMATION

A-_kn-gt KINTORE TONALITE: medium-grained biotite tonalite

A-_lb-gg LIBERTY GRANODIORITE: fine- to coarse-grained granodiorite; local monzogranite; massive; contacts discordant with greenstones and early foliation

A-_ld-gm LAKE DUNDAS MONZOGRANITE: medium- to coarse-grained, equigranular biotite monzogranite

A-_lz-gt LAKE BRAZIER TONALITE: highly variable biotite- and hornblende-bearing tonalite to granodiorite

A-_mn-gm MENANGINA MONZOGRANITE: biotite monzogranite with prominent K-feldspar megacrysts; cut by pegmatite and microgranitic dykes

A-_mu-gm MUNGARI MONZOGRANITE: medium-grained, equigranular, biotite–muscovite monzogranite; massive

A-_mw-ge McAULIFFE WELL SYENITE: medium- to coarse-grained quartz syenite; K-feldspar megacrysts


48

A-_my-gm MYSTERY MONZOGRANITE: fine-grained, equigranular biotite monzo-granite

A-_nm-gm NINE MILE MONZOGRANITE: coarse-grained, porphyritic, biotite monzogranite; penetrative foliation moderate to weak, strongest at contacts with greenstones; domal core to regional (D2) anticline

A-_on-gm LONE HAND MONZOGRANITE: leucocratic monzogranite; massive; contacts discordant with greenstones and foliation in early granite

A-_ot-gg OLIVER TWIST GRANODIORITE: biotite granodiorite, local monzogranite; domal within D2 antiform; sheared contacts with greenstones

A-_pi-gm PIONEER MONZOGRANITE: foliated biotite monzogranite; gneiss enclaves

A-_po-gc PORPHYRY QUARTZ MONZONITE: medium- to coarse-grained quartz monzonite; biotite after hornblende; prominent K-feldspar phenocrysts

A-_rh-g RED HILL GRANITE: syenogranite, porphyritic monzogranite, and grano-diorite

A-_ro-gm ROWLES LAGOON MONZOGRANITE: medium- to coarse-grained biotite monzogranite; local plagioclase pheno-crysts; foliated

A-_st-gm SILT DAM MONZOGRANITE: seriate biotite monzogranite; marginal zones have contact-parallel foliation with steep mineral lineation

A-_tg-gm TWO GUM MONZOGRANITE: medium-grained, porphyritic, biotite–hornblende monzogranite

A-_tr-gm THEATRE ROCKS MONZOGRANITE: fi ne- to medium-grained, equigranular biotite monzogranite to granodiorite; post-D2 to syn-D3

A-_ul-gm ULARRING MONZOGRANITE: even-grained monzogranite

A-_wa-gc WADARRAH QUARTZ MONZONITE: hornblende-bearing quartz monzonite with local platy mineral alignment

A-_we-gga WEEBO GRANODIORITE: fi ne-grained granodiorite

A-_we-ggd WEEBO GRANODIORITE: very coarse grained granodiorite

A-_wi-gm WIDGIEMOOLTHA MONZOGRANITE: foliated porphyritic monzogranite; microcline porphyroclasts

A-_wo-gm WOOLGANGIE MONZOGRANITE: recrystallized monzogranite and grano-diorite

A-_yi-gm YINDI MONZOGRANITE: fine- to medium-grained, equigranular monzo-granite

A-_yr-gm YARRI MONZOGRANITE: biotite monzogranite; K-feldspar phenocrysts; pervasive foliation and quartz veins are folded locally

Archaean granitic suites

A-ER-g Erayinia Granitic Suite: syenite to monzo-granite; hornblende or clinopyroxene bearing; massive to moderately foliated; strong shearing in mafi c enclaves

Archaean layered mafi c to ultramafi c intrusions — named

A-KV-gu Kathleen Valley Intrusion: quartz gabbro and tonalite; metamorphosed

A-KV-oa Kathleen Valley Intrusion: anorthositic gabbro and anorthosite; metamorphosed

A-KV-og Kathleen Valley Intrusion: gabbro; meta-morphosed

A-KV-ogq Kathleen Valley Intrusion: quartz-bearing gabbro and quartz gabbro; metamorphosed

A-KV-ogx Kathleen Valley Intrusion: pyroxene-rich gabbro; metamorphosed

A-KV-ogy Kathleen Valley Intrusion: layered gabbro with rhythmic layering (2–10 cm) due to varying proportions of amphibole and plagioclase; metamorphosed

A-ME-gu Mount Ellis Intrusion: iron-rich quartz gabbro with granophyric segregations; metamorphosed

A-ME-og Mount Ellis Intrusion: gabbro; meta-morphosed

A-ME-ogl Mount Ellis Intrusion: leucogabbro and plagioclase-rich gabbronorite; meta-morphosed

A-ME-ax Mount Ellis Intrusion: pyroxenite; metamorphosed

A-MI-og Mission Intrusion: gabbro; meta-morphosed

A-MI-ap Mission Intrusion: peridotite; meta-morphosed

A-MI-ax Mission Intrusion: pyroxenite; meta-morphosed

A-MM-og Mount Monger Sill: gabbro; relict cumulate texture; metamorphosed

A-MP-gv Mount Pleasant Intrusion: i ron-rich granophyre marker horizon; metamorphosed

A-MP-og Mount Pleasant Intrusion: gabbro; meta-morphosed

A-MP-ogl Mount Pleasant Intrusion: leucogabbro and plagioclase-rich gabbronorite; metamorphosed


A-MP-om Mount Pleasant Intrusion: gabbronorite marker horizon; metamorphosed

A-MP-ad Mount Pleasant Intrusion: massive olivine cumulate (dunite) at base; metamorphosed

A-MP-ax Mount Pleasant Intrusion: pyroxenite; metamorphosed

A-MT-gu Mount Thirsty Intrusion: quartz gabbroic and granophyric segregations in gabbro; metamorphosed

A-MT-og Mount Thirsty Intrusion: gabbro; minor granophyric and quartz gabbro; metamorphosed

A-MT-ap Mount Thirsty Intrusion: peridotite; metamorphosed

A-MT-ax Mount Thirsty Intrusion: pyroxenite; includes dunite and olivine bronzitite layers and minor peridotite; meta-morphosed

A-OB-gu Ora Banda Intrusion: quartz gabbro and granophyre; late differentiate; meta-morphosed

A-OB-om Ora Banda Intrusion: gabbronorite; metamorphosed

A-OB-ad Ora Banda Intrusion: massive olivine cumulate (dunite) at base; meta-morphosed

A-OB-ax Ora Banda Intrusion: bronzitite and norite; metamorphosed

A-OH-og Oak Hill Sill: gabbro; relict cumulate texture; metamorphosed

A-OR-gv Orinda Intrusion: iron-rich granophyre; metamorphosed

A-OR-og Orinda Intrusion: gabbro; meta-morphosed

A-PW-og Powder Intrusion: gabbro; meta-morphosed

A-PW-ogl Powder Intrusion: leucogabbro; meta-morphosed

A-SE-og Seabrook Intrusion: gabbro with subordinate pyroxenite; metamorphosed

A-SE-ap Seabrook Intrusion: peridotite, commonly altered to a talc–carbonate assemblage; cumulate texture; metamorphosed

A-SE-ax Seabrook In t rus ion: pyroxeni te , gradational contact with overlying gabbro; metamorphosed

A-TM-og Three Mile Intrusion: gabbro; meta-morphosed

Archaean mafi c intrusive rocks

A-moa Amphibolite; medium- to coarse-grained, derived from gabbro

A-mogd Epidotized gabbro

A-mogs Strongly foliated gabbro

4


A-o Mafi c intrusive rock, undivided; meta-morphosed; includes deeply weathered rocks

A-oa Anorthosite; metamorphosed

A-od Dolerite; minor basalt or gabbro components; metamorphosed

A-ode Dolerite, equigranular; metamorphosed

A-odp Porphyritic dolerite, with feldspar phenocrysts; metamorphosed

A-og Gabbro; minor pyroxenite or quartz gabbro components; metamorphosed

A-ogd Gabbro, very coarse grained; meta-morphosed

A-oge Gabbro, equigranular; metamorphosed

A-ogl Leucogabbro; locally magnetite rich; metamorphosed

A-ogp Porphyritic gabbro with plagioclase phenocrysts; metamorphosed

A-ogq Quartz-bearing gabbro and quartz gabbro; late differentiation product; granophyric; metamorphosed

A-ogx Pyroxenitic gabbro with minor pyroxenite; feldspar phenocrysts locally; meta-morphosed

A-ol Olivine gabbronorite; olivine–plagioclase orthocumulate at base of layered sills; metamorphosed

A-oo Olivine gabbro; metamorphosed

A-ow Norite and gabbronorite; metamorphosed

Archaean mafi c intrusive rocks — named

A-_kk-og KILKENNY GABBRO: gabbro and olivine–plagioclase to pyroxene–plagioclase cumulate rocks; meta-morphosed

Archaean chemical sedimentary rocks

A-mi Metamorphosed banded iron-formation, s i l icate facies; quartz–magneti te(–grunerite–hornblende) rock

A-cc Chert and banded chert; locally includes silicifi ed (black) shale, slate, or exhalite; metamorphosed

A-ccb Grey and white banded chert, locally iron rich; metamorphosed; includes meta-morphosed siliceous grey–black shale, slate, and mylonite

A-ccx Chert breccia, commonly cemented with goethite; metamorphosed

A-cib Banded iron-formation, oxide facies; fi nely interleaved magnetite- and quartz-rich chert and/or siliceous slate; meta-morphosed

9


A-cij Jaspilite; metamorphosed

A-kd Dolomite; metamorphosed

A-kl Limestone; metamorphosed

Archaean clastic sedimentary rocks

A-md Metasedimentary rock, undivided; includes pelitic and psammitic rocks, metaconglomerate, metachert, and meta-morphosed felsic volcanic and epiclastic rocks

A-mda Para-amphibolite

A-mdfs Quartzofeldspathic to micaceous meta-sedimentary rock derived from felsic volcanic and volcaniclastic rocks; commonly schistose; includes pelite, slate, chloritic and carbonate-bearing schist, and garnet–biotite schist; local andalusite and/or garnet porphyroblasts

A-mhs Psammitic and pelitic rocks: banded quartzofeldspathic to chloritic schist, with interlayered quartz–mica schist; derived from felsic and mafi c igneous rocks

A-mlpd Phyllite with abundant andalusite porphyroblasts

A-mls Pelitic rock with local andalusite, kyanite, garnet, staurolite, and/or cordierite porphyroblasts; includes minor psammite; commonly schistose

A-mlv Grey to black slate and interlayered quartzofeldspathic schist with chert layers and lenses; locally ferruginous and/or pyritic

A-mlvk Carbonatized fine-grained metasedi-mentary rock (subsurface only)

A-mtq Medium-grained quartzite; local meta-morphosed quartz siltstone and quartz–muscovite schist

A-mtqs Cream and brown, layered, foliated and mylonitic quartzite and associated fi ne-grained siliceous rocks

A-mx Metamorphosed conglomerate; pebbles of amphibole–feldspar–quartz–garnet rock and feldspar-phyric felsic schist

A-s Sedimentary rock, undivided; includes sandstone, siltstone, shale, and chert; metamorphosed; commonly deeply weathered

A-sc Conglomerate with subordinate sandstone; pebbles and boulders include granitic, chert, felsic porphyritic rock, and mafi c rock; matrix or clast supported; metamorphosed

A-scc Conglomerate and breccia with chert clasts and fi ne-grained siliceous matrix; metamorphosed

A-scf Oligomictic conglomerate with clasts mainly of felsic volcanic rock; subordinate sandstone; metamorphosed

50

A-scq Oligomictic conglomerate with clasts mainly of quartz, quartzite, and chert; metamorphosed

A-sgb Conglomerate and subordinate pebbly sandstone with basalt and gabbro clasts; metamorphosed

A-sgf Conglomerate, sandstone and tuff with dominantly andesitic clasts; epiclastic; metamorphosed

A-sh Shale with subordinate chert; minor siltstone and sandstone; variably foliated; commonly silicifi ed; metamorphosed; may include some slate and phyllite

A-shh Graphitic shale; metamorphosed; includes slate

A-shq Shale and siltstone with local quartz granules; metamorphosed

A-sl Siltstone; metamorphosed

A-slc Brown, fi ne-grained quartzofeldspathic rock with local banded chert pebbles; associated with grey–white banded chert; metamorphosed

A-snf Sedimentary rocks derived from felsic volcanic and volcaniclastic rocks; epiclastic; metamorphosed; variably foliated; commonly deeply weathered and kaolinized

A-sp Sandstone and conglomerate; meta-morphosed

A-sr Quartzofeldspathic pebbly sandstone; epiclastic; metamorphosed

A-ss Sandstone to siltstone; local conglomerate; metamorphosed

A-st Sandstone; locally pebbly; subordinate conglomerate and siltstone; epiclastic or argillaceous; metamorphosed

A-sti Ferruginous sandstone; includes green quartzite and mica schist; metamorphosed

A-stq Medium- to coarse-grained, quartz-rich sandstone; metamorphosed; common micaceous intervals; locally fuchsitic; local quartzite

A-sw Poorly sorted wacke; local grading from wacke to shale; metamorphosed

A-swa Arkose; metamorphosed

A-swb Feldspathic/lithic wacke with amphibole, derived from volcanic to volcaniclastic rocks; metamorphosed

A-sx Sedimentary breccia; metamorphosed

Archaean sedimentary formationsA-_b-mh MOUNT BELCHES FORMATION:

interbanded quartz–feldspar–biotite


psammite and biotite–quartz–feldspar(–ch lor i t e–muscovi te–s tauro l i t e–andalusite–sillimanite–garnet) pelite, after graded wacke–mudstone units

A-_b-mhe MOUNT BELCHES FORMATION: hornfelsed wacke and mudstone, including biotite, hornblende, clinopyroxene, or sillimanite hornfels; primary compositional layering preserved

A-_b-mhz MOUNT BELCHES FORMATION: metasomatized wacke and mudstone, including para-amphibolite, amphibole-bearing quartzite, biotitic psammite, and chlorite-bearing quartzite; as selvedges to laminated quartz veins, adjacent to faults, or as irregular masses

A-_b-ml MOUNT BELCHES FORMATION: bioti te–quartz–feldspar(–chlori te–muscovi te–s taurol i te–andalus i te–sillimanite–garnet) pelite, after mudstone

A-_b-mt MOUNT BELCHES FORMATION: quartz–feldspar–biot i te(–chlori te) psammite, after wacke; cross-bedding, channels, and parallel lamination locally common; tops of units may be biotitic after mudstone; includes subordinate graded wacke–mudstone (A-_b-mh) and mudstone (A-_b-ml) units

A-_b-s MOUNT BELCHES FORMATION: undivided and commonly deeply weathered; varying proportions of wacke and mudstone, typically biotitic; rare banded iron-formation and pebbly sandstone beds; generally weakly metamorphosed and locally strongly hornfelsed

A-_bn-sw MOUNT BELCHES FORMATION: Santa Claus Member: wacke, mudstone, and ferruginous mudstone laterally grading into cherty iron-formation; common Bouma sequences with magnetite concentrated in the pelitic portion; metamorphosed

A-_jc-scp JONES CREEK CONGLOMERATE: polymict ic conglomerate ; meta-morphosed

A-_jc-sgg JONES CREEK CONGLOMERATE: conglomerate and sandstone; dominantly granitic clasts in quartzofeldspathic matrix; metamorphosed

A-_jc-sgp JONES CREEK CONGLOMERATE: conglomerate and sandstone with mafi c and granitic clasts and dominantly mafi c matrix; metamorphosed

A-_jc-sta JONES CREEK CONGLOMERATE: arkosic sandstone, fi ne to medium grained; rare pebbles; metamorphosed

A-_kw-sc KURRAWANG FORMATION: lower unit: conglomerate, sandy conglomerate, and pebbly sandstone; metamorphosed

51


A-_kw-sci KURRAWANG FORMATION: lower unit: conglomerate with banded iron- formation clasts (magnetic horizon); metamorphosed

A-_kw-st KURRAWANG FORMATION: upper unit: sandstone and pebbly sandstone; metamorphosed

A-_me-st MEROUGIL FORMATION: biotite-bearing pebbly sandstone, sandstone, and siltstone; metamorphosed

Archaean volcanic and volcaniclastic rocks

A-mvks Strongly deformed and carbonatized, interleaved mafi c and ultramafi c volcanic and felsic volcaniclastic rocks

A-mvfs Felsic schist, after volcanic and/or volcaniclastic rock

A-mvs Mafi c to felsic schist with fi ne layering and small hornblende and feldspar fragments, after volcanic and/or volcaniclastic rock

Archaean felsic volcanic and subvolcanic rocks

A-mfas Schist derived from andesitic and dacitic volcanic and volcaniclastic rock

A-mfs Quartzofeldspathic micaceous schist derived from felsic volcanic or volcani-clastic protolith

A-mfsa Hornblende–biotite–quartz–feldspar(–garnet) schist; variable hornblende content; andesitic protolith; locally interlayered with felsic and mafi c schists

A-mfsc Schist with feldspar clasts and chlorite aggregates; includes chlorite–carbonate, chlorite–sericite, and epidote–chlorite schists

A-mfsd Aluminous schist with andalusite porphyroblasts derived from palaeosols in felsic volcanic and volcaniclastic rocks

A-mfss Foliated felsic rock

A-f Felsic volcanic and volcaniclastic rocks, metamorphosed; commonly deeply weathered and kaolinized

A-fa Andesite, commonly with plagioclase and/or hornblende phenocrysts; meta-morphosed

A-fab Flow-banded trachyandesitic rock; metamorphosed

A-fap Porphyritic andesite, volcanic or subvolcanic; numerous plagioclase phenocrysts; metamorphosed; variably foliated

A-fav Andesitic volcanic and volcaniclastic rock; common fragmental textures; meta-


morphosed; local epidote and carbonate alteration

A-fcp Rhyodacite; porphyritic; rarely spherulitic; metamorphosed

A-fd Dacite; commonly tuffaceous; locally brecciated; includes minor rhyolite, rhyodacite, and andesite; metamorphosed

A-fdp Feldspar–quartz porphyritic rock; dacitic to rhyolitic; volcanic or subvolcanic; metamorphosed; locally schistose

A-fn Volcanic and volcaniclastic felsic rock, undivided; andesite to dacite and rhyolite, minor basaltic andesite; local fragmental textures; metamorphosed; variably foliated and chloritized; local schist and meta-wacke interlayers

A-fnpi Quartz–feldspar porphyritic rock, with xenoliths; metamorphosed

A-fnv Volcaniclastic rock ranging from andesite to basaltic andesite in composition; fragmental textures common; meta-morphosed

A-fr Rhyolite lava fl ows, quartz phyric, locally tuffaceous; weak to schistose foliation; metamorphosed

A-frp Quartz–feldspar porphyritic rock; metamorphosed; weak to schistose foliation

A-frt Felsic tuff and tuffaceous rock; fi nely banded; fi ne to medium grained; rhyolite to dacite with quartz and feldspar phenocrysts; metamorphosed; variably foliated

A-frth Felsic lapilli tuff; metamorphosed

A-frv Ignimbrite; metamorphosed

A-xfrv-ftv Mixed rhyolitic and trachytic tuff and oligomictic breccia; metamorphosed

A-frvt Bedded felsic volcaniclastic rock with minor felsic volcanic rock; meta-morphosed

A-frxl Rhyolitic to rhyodacitic oligomictic breccia and tuff; massive to poorly bedded, with lithic clasts (>1 cm) in fi ne-grained to glassy matrix; includes some felsic volcanic rock; metamorphosed

Archaean mafi c volcanic and subvolcanic rocks

A-xmb-mg Metamafi c rock interleaved with minor foliated granitic rock

A-mbba Amphibolite, fi ne to medium grained; commonly weakly foliated or massive; derived from basalt

A-xmbba-md Amphibolitic metabasalt interlayered with mafic and quartzitic metasedimentary rocks

52

A-mbbd Epidotized basalt

A-mbbe Hornfelsed basalt

A-mbbk Basalt and locally amygdaloidal fine-grained mafic rock, strongly carbonatized; includes massive carbonate lenses

A-mbbs Fine-grained schist derived from basalt; amphibole–chlorite assemblages; locally strongly metasomatized

A-xmbbs-mfs Basaltic schist interleaved with feldspar-phyric schist

A-mbdd Basaltic andesite and andesite, epidotized; foliated

A-mbdk Carbonatized (massive) basaltic andesite

A-mbps Foliated pyroxene spinifex-textured basalt

A-mbs Foliated fi ne-grained mafi c rock; locally hornfelsed or epidotized

A-xmbs-md Metabasalt and fi ne-grained hornblende schist interlayered with metasedi-mentary rocks

A-b Fine to very fi ne grained mafi c rock, undivided; metamorphosed; commonly deeply weathered

A-bb Basalt; locally porphyritic; meta-morphosed; includes dolerite-textured zones and feldspar–hornblende or chlorite schist

A-xbb-f Bimodal volcanic sequence, basalt with interlayers of rhyolite or dacite; metamorphosed

A-bba Basalt, aphyric; metamorphosed

A-bbd Pillowed, variolitic basalt; local pyroxene-spinifex texture; metamorphosed

A-bbg Amygdaloidal basalt; metamorphosed

A-bbo Pillow basalt; flow-top breccia with varioles or spinifex locally; meta-morphosed; includes Kambalda Footwall basalt

A-bbp Porphyritic to glomeroporphyritic basalt; fi ne to coarse plagioclase phenocrysts; metamorphosed; local intense epidot-ization

A-bbq Porphyritic basalt with relict plagioclase phenocrysts; fine-grained basalt with common coarser grained, dolerite-textured layers or zones; metamorphosed

A-bbt Basaltic tuff, metamorphosed (subsurface only)

A-bbw Variolitic basalt; metamorphosed

A-bbx Basaltic fragmental rock; agglomerate, or hyaloclastite peperite or breccia; metamorphosed

A-bby Basalt to dolerite; interleaved units of fi ne-grained basalt with coarser layers or zones

GSWA Report 95 East Yilgar

(probably differentiated flows); meta-morphosed

A-bd Basaltic andesite and andesite; plagioclase and hornblende phenocrysts; locally fragmental; variably foliated; chlorite and carbonate alteration common; meta-morphosed

A-bdp Basaltic andesite with plagioclase phenocrysts; metamorphosed; variably foliated

A-bn Basaltic rock, undivided; includes basaltic fl ow units with doleritic to gabbroic zones, pillowed basalt, and subvolcanic sills; metamorphosed

A-bs Pyroxene spinifex-textured basalt; locally variolitic and/or pillowed; meta-morphosed

Archaean mafi c volcanic rocks — named

A-_mg-bb MOUNT GOODE BASALT: tholeiitic basalt; metamorphosed

A-_mg-bbp MOUNT GOODE BASALT: plagioclase-phyric tholeiitic basalt; phenocrysts up to 20 cm long; metamorphosed

Archaean ultramafi c volcanic and subvolcanic rocks

A-mu Metamorphosed ul t ramafic rock, undivided; includes talc–chlorite(–carbonate) and tremolite–chlorite schist

A-mukk Komatiite, extensively carbonatized; includes carbonate–talc–chlorite schist and massive carbonate lenses

A-xmus-mbs Interleaved ultramafi c and mafi c schist

A-musc Chlorite schist

A-musk Talc–carbonate(–serpentine) rock; commonly schistose

A-musr Tremolite(–chlorite–talc–carbonate) schist; locally serpentinized; komatiitic or pyroxenitic protolith

A-must Talc–chlorite(–carbonate) schist; minor tremolite–chlorite schist

A-mut Serpentinite, commonly massive; derived from ultramafi c volcanic rocks

A-uk Komatiite and komatiite fl ow units; olivine spinifex texture and locally well developed cumulate zones; metamorphosed to tremolite–chlorite, serpentine, and carbonate assemblages; silicified or weathered

A-uko Komatiite (as for A-uk), pillowed to massive; metamorphosed

A-up Peridotite; relict olivine-cumulate texture; minor pyroxenite; commonly serpentin-

53

n 1:100 000 Geological Information Series — an explanatory note

itized and locally rodingitized or silicifi ed; metamorphosed

A-uu Dunite; massive serpentinite with preserved olivine-cumulate microstructures; metamorphosed

A-ux Pyroxenite; commonly associated with peridotite in minor layered sills; metamorphosed; variably altered to tremolite; locally schistose

ReferencesHOCKING, R. M., LANGFORD, R. L., THORNE, A. M., SANDERS,

A. J., MORRIS, P. A., STRONG, C. A., and GOZZARD, J. R., 2001, A classifi cation system for the regolith in Western Australia: Western Australia Geological Survey, Record 2001/4, 22p.

TYLER, I. M., MORRIS, P. A., THORNE, A. M., SHEPPARD, S., SMITHIES, R. H., RIGANTI, A., DOYLE, M. G., and HOCKING, R. M., in prep., The revised GSWA rock classifi cation scheme: Western Australia Geological Survey, Annual Review 2003–04.

TYLER, I. M., and HOCKING, R. M., 2001, Tectonic units of Western Australia (scale 1:2 500 000): Western Australia Geological Survey.)


Appendix 2

WAMIN database

5

WAMIN database (mineral occurrences)The WAMIN (Western Australian mineral occurrence) database of the Geological Survey of Western Australia (GSWA) contains geoscience attribute information on mineral occurrences in Western Australia. The database includes textual and numeric information on the location of the occurrences, location accuracy, mineral commodities, mineralization-style classifi cation, order of magnitude of resource tonnage and estimated grade, ore and gangue mineralogy, details of host rocks, and both published and unpublished references. Each of the occurrences in WAMIN is identifi ed by a unique ‘deposit number’.

The WAMIN database uses a number of authority tables to constrain the essential elements of a mineral occurrence, such as the operating status, the commodity group, and the style of mineralization. These and other attributes were extracted either from open-fi le mineral exploration reports in WAMEX (Western Australian mineral exploration database) or from the published literature.

Those elements of the database that may be used to create the symbols for mineral occurrences and tabular information are:• occurrence number and name (deposit number and

name);• operating status (font style of deposit number);• position and spatial accuracy (symbol position);• commodity group (symbol colour);• mineralization style (symbol shape).

These parameters have previously been defi ned for the GSWA mineralization mapping projects that have been completed for prospectivity enhancement studies of southwest Western Australia (Hassan, 1998), the north Eastern Goldfi elds (Ferguson, 1998), the Bangemall Basin (Cooper et al., 1998), the west Pilbara (Ruddock, 1999), the east Kimberley (Hassan, 2000), the east Pilbara (Ferguson and Ruddock, 2001), and the north Kimberley (Ruddock, 2003).

Operating status

The database includes mineralization sites (referred to as deposits) ranging from small, but mineralogically signifi cant, mineral occurrences up to operating mines. The classifi cation includes all MINEDEX sites with established resources: MINEDEX is the Department of Industry and Resources (DoIR) mines and mineral deposits information database (Townsend et al., 1996, 2000; Cooper et al., 2003). All occurrences in the WAMIN database are assigned a unique, system-generated number (deposit number). The system used is:• Mineral occurrence — any outcropping mineralization

4

or gossan or any drill intersection of an economic mineral exceeding an agreed concentration and size found in bedrock or regolith.

• Prospect — any mineralized zone that has not been suffi ciently sampled at the surface, or in the subsurface, to enable a resource to be identifi ed. A prospect may also be old workings.

• Mineral deposit — economic mineralization for which there is an established resource fi gure.

• Abandoned mine — workings that are no longer operating, or are not on a care-and-maintenance basis, and for which there is recorded production, or where fi eld evidence suggests that the workings were for more than prospecting purposes.

• Operating mine — workings that are operating, including on a care-and-maintenance basis, or that are in development leading to production.

The names of the occurrences, and any synonyms that may have been used, are mainly derived from the published literature and from open-fi le reports (in WAMEX); others are assigned according to the nearest geographical feature. Names that appear in the MINEDEX database have been used where possible, although there may be differences created because MINEDEX uses site names based on overall production and resources, where WAMIN may show names of several individual occurrences at one MINEDEX site.

Commodity group

The WAMIN database includes a broad grouping that is based on the potential end-use or typical end-use of the principal commodities comprising a mineral occurrence. The commodity group, as listed in Table 2.1, are typically identifi ed by particular colours of mineral occurrence symbols.

The commodity groupings are based on those published by the Mining Journal Limited (1998) with modifi cations, as shown in Table 2.2, to suit the range of minerals and end-uses for the mineral output of Western Australia.

Mineralization style

There are a number of detailed schemes for classifying mineral occurrences into groups representing different styles of mineralization, with the scheme of Cox and Singer (1986) probably being the most widely used. The application of this scheme in Western Australia would necessitate modifi cations to an already complex scheme, along the lines of those adopted by the Geological Survey of British Columbia (Lefebure and Ray, 1995; Lefebure and Hoy, 1996).

The Geological Survey of Western Australia has


Table 2.1. WAMIN authority table for commodity groups

WAMIN commodity group Typical commodities Symbol colour

Precious mineral Diamond, semi-precious gemstones

Precious metal Ag, Au, PGE

Steel-industry metal Co, Cr, Mn, Mo, Ni, V, W

Speciality metal Be, Li, Nb, REE, Sn, Ta, Ti, Zr

Base metal Cu, Pb, Sb, Zn

Iron Fe

Aluminium Al (bauxite)

Energy Coal, U

Industrial mineral Asbestos, barite, fl uorite, kaolin, talc

Construction material Clay, dimension stone, limestone

Table 2.2. Modifi cations made to the Mining Journal Ltd (1998) commodity classifi cation

Commodity group Commodities Changes made for WAMIN commodity group(Mining Journal Ltd, 1998) (see Table 2.1)

Precious metals and minerals Au, Ag, PGE, diamonds, Diamond and other gemstones in precious minerals group; other gemstones Au, Ag, and PGE in precious metals group

Steel-industry metals Iron ore, steel, ferro-alloys, Fe in iron group Ni, Co, Mn, Cr, Mo, W, Nb, V

Speciality metals Ti, Mg, Be, REE, Zr, Hf, Li, Sn added from major metals; Sb into the base metals group Ta, Rh, Bi, In, Cd, Sb, Hg

Major metals Cu, Al, Zn, Pb, Sn Cu, Pb, and Zn into the base metals group; Al (bauxite) into aluminium group; Sn in speciality metals

Energy Coal, U No change

Industrial minerals Asbestos, sillimanite minerals, No change phosphate rock, salt, gypsum, soda ash, potash, boron, sulfur, graphite, barite, fl uorspar, vermiculite, perlite, magnesite/ magnesia, industrial diamonds, kaolin

55


Table 2.3. WAMIN authority table for mineralization styles and groups

Mineralization style Typical commodities

Carbonatite and alkaline igneous intrusions Nb, Zr, REE, PKimberlite and lamproite Diamond

Disseminated and stockwork in plutonic intrusions Cu, Mo, AuGreisen SnPegmatitic Sn, Ta, Nb, LiSkarn W, Mo, Cu, Pb, Zn, Sn

Orthomagmatic mafi c and ultramafi c — komatiitic or dunitic Ni, Cu, Co, PGEOrthomagmatic mafi c and ultramafi c — layered-mafi c intrusions Ni, Cu, Co, V, Ti, PGE, CrOrthomagmatic mafi c and ultramafi c — undivided Ni, Cu, Co, V, Ti, PGE, Cr

Vein and hydrothermal — undivided Au, Ag, Cu, Pb, Zn, Ni, U, Sn, F

Stratabound volcanic and sedimentary — volcanic-hosted sulfi de Cu, Zn, Pb, Ag, Au, BaStratabound volcanic and sedimentary — sedimentary-hosted sulfi de Pb, Zn, Cu, AgStratabound volcanic and sedimentary — volcanic oxide Fe, P, CuStratabound volcanic and sedimentary — undivided Pb, Zn, Cu, Ag, Au, Fe, Ba

Stratabound sedimentary — carbonate-hosted Pb, Zn, Ag, CdStratabound sedimentary — clastic-hosted Pb, Zn, Cu, Au, Ag, Ba, Cd, UStratabound sedimentary — undivided Pb, Ba, Cu, AuSedimentary — banded iron-formation (supergene enriched) FeSedimentary — banded iron-formation (taconite) FeSedimentary — undivided Mn

Sedimentary — basin Coal, bitumen

Regolith — alluvial to beach placers Au, Fe pisolites, Ti, Zr, REE, diamond, SnRegolith — calcrete U, VRegolith — residual and supergene Al, Au, Ni, Co, Mn, V, Fe crustals, Fe screeRegolith — residual to eluvial placers Au, Sn, Ti, Zr, REE, diamond

Undivided Construction materials, various

56

Table 2.4. Suggested minimum intersections for mineral occurrences in drillholes or trenches

Element Intersection length Grade (m)

Hard rock and lateritic depositsGold >1 >0.5 ppmSilver >1 >35 ppmPlatinum >1 >0.7 ppmLead >1 >1%Zinc >1 >0.5%Copper >1 >0.25%Nickel >1 >0.2%Cobalt >1 >0.02%Chromium >1 >5% Cr2O3

Vanadium >5 >0.1%Tin >5 >0.02%Iron >5 >40% FeManganese >5 >25%Uranium >2 >300 ppm UDiamonds na any diamondsTantalum >5 >200 ppmTungsten >1 >1000 ppm (0.1%)

Placer depositsGold na >300 mg/m3 in bulk sampleDiamonds na any diamondsHeavy minerals >5 >2% ilmenite

NOTE: Modifi ed from Rogers and Hart (1995) na: not applicable

adopted the principles of ore deposit classifi cation from Evans (1987) with some modifi cations based on Edwards and Atkinson (1986). This scheme works on the premise that ‘If a classifi cation is to be of any value it must be capable of including all known ore deposits so that it will provide a framework and a terminology for discussion and so be of use to the mining geologist, the prospector and the exploration geologist’. The system above is based on an environmental–rock association classification, with elements of genesis and morphology where they serve to make the system simpler and easier to apply and understand (Table 2.3).

Mineral occurrence determination limits

Any surface expression of mineralization (gossan or identifi ed economic mineral) is an occurrence. Subsurface or placer mineralization is included as an occurrence where it meets the criteria given in Table 2.4.

Professional judgement is used if shorter intercepts or surface occurrences at higher grade (or vice versa) are involved. Any diamonds or gemstones would be mineral occurrences, including diamondiferous kimberlite or


lamproite.

ReferencesCOOPER, R. W., FLINT, D. J., and SEARSTON, S. M., 2003,

Mines and mineral deposits of Western Australia: digital extract from MINEDEX — an explanatory note, 2002 update: Western Australia Geological Survey, Record 2002/19.

COOPER, R. W., LANGFORD, R. L., and PIRAJNO, F., 1998, Mineral occurrences and exploration potential of the Bangemall Basin: Western Australia Geological Survey, Report 64, 42p.

COX, D. P., and SINGER, D. A., 1986, Mineral deposit models: United States Geological Survey, Bulletin 1693, 379p.

EDWARDS, R., and ATKINSON, K., 1986, Ore deposit geology and its infl uence on mineral exploration: London, Chapman and Hall, 466p.

EVANS, A. M., 1987, An introduction to ore geology: Oxford, Blackwell Scientifi c Publications, 358p.

FERGUSON, K. M., 1998, Mineral occurrences and exploration potential of the north Eastern Goldfi elds: Western Australia Geological Survey, Report 63, 40p.

FERGUSON, K. M., and RUDDOCK, I., 2001, Mineral occurrences and exploration potential of the east Pilbara: Western Australia Geological Survey, Report 81, 114p.

HASSAN, L. Y., 1998, Mineral occurrences and exploration potential of southwest Western Australia: Western Australia Geological Survey, Report 65, 38p.

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HASSAN, L. Y., 2000, Mineral occurrences and exploration potential of the east Kimberley: Western Australia Geological Survey, Report 74, 83p.

LEFEBURE, D. V., and HOY, T., (editors), 1996, Selected British Columbia Mineral Deposit Profi les, Volume 2 — Metallic Deposits: British Columbia Ministry of Employment and Investment, Open File 1996-13, 171p.

LEFEBURE, D. V., and RAY, G. E., (editors), 1995, Selected British Columbia Mineral Deposit Profi les, Volume 1 — Metallics and Coal: British Columbia Ministry of Employment and Investment, Open File 1995-20, 135p.

MINING JOURNAL LIMITED, 1998, Mining Annual Review, Volume 2 — Metals & Minerals: London, Mining Journal Ltd, 112p.

ROGERS, M. C., and HART, C. N., 1995, Procedural guidelines for qualitative mineral potential evaluations by the Ontario Geological Survey: Canada, Ontario Geological Survey, Open File Report OFR 5929 (unpublished).

RUDDOCK, I., 1999, Mineral occurrences and exploration potential of the west Pilbara: Western Australia Geological Survey, Report 70, 63p.

RUDDOCK, I., 2003, Mineral occurrences and exploration potential of the north Kimberley: Western Australia Geological Survey, Report 85, 58p.

TOWNSEND, D. B., GAO MAI, and MORGAN, W. R., 2000, Mines and mineral deposits of Western Australia: digital extract from MINEDEX — an explanatory note: Western Australia Geological Survey, Record 2000/13, 28p.

TOWNSEND, D. B., PRESTON, W. A., and COOPER, R. W., 1996, Mineral resources and locations, Western Australia: digital dataset from MINEDEX: Western Australia Geological Survey, Record 1996/13, 19p.

7


Appendix 3

Gazetteer of localities

___ MGA coordinates ___Locality Easting Northing

Abercromby 220200 7024100Agnew 255800 6899300Barratt Well 471840 6722790Boorara Hill 371375 6590875Brady Well 394650 6704780Bulong 384800 6597400Carr Boyd Rocks 367600 6673100Cawse 321900 6638800Cleo–Sunrise 443500 6783100Comet Vale 318840 6686100Coolgardie 324800 6574200Corsair 366700 6596000Darlot mining centre 329600 6914000Davyhurst 273400 6673900Democrat 446200 6757100Diorite Hill 469300 6838600Eucalyptus 416500 6774100Famous Blue 408700 6950700Gindalbie 380700 6649300Goongarrie 311500 6681000Granny Smith 442800 6813000Hanns Camp 452700 6838500Higginsville 377700 6487200Hinkler Well 220200 7024100Hootanui 398400 6957500Jeedamya 332580 6746170Joes Bore 271310 6889280Kalgoorlie–Boulder 353900 6597500Kambalda 367500 6551400Kathleen Valley mining centre 260600 6953100Kookynie 353640 6754320Kurrajong 316100 6822600Lake Cowan 396000 6492000Lake Lefroy 375000 6537000Lake Maitland 311600 6996900Lake Miranda 259600 6937800Lake Ward 271000 7088000Lake Way 237300 7044100Laverton 441300 6833400Lawlers 258100 6892000Leinster 273400 6910300Leonora 337200 6803600Londonderry 316600 6558100Marshall Creek 303500 6865900Marshall Pool 305700 6862400

5

___ MGA coordinates ___Locality Easting Northing

Melita 348830 6784890Menzies 309300 6713500Minerie Hill 379500 6825500Mount Amy 433200 6896100Mount Charlotte 354280 6598430Mount Clifford 310300 6849500Mount Grey 317800 6966400Mount Joel 306680 6985790Mount Keith 256400 6992400Mount Lucky 452200 6816200Mount Malcolm 380150 6794675Mount Margaret Mission 420500 6814400Mount McKenna 455800 6840400Mount Melita 351000 6780600Mount Molybdenite 343750 6831750Mount Pleasant 332100 6622500Mount Stirling 311500 6833300Mount Varden 440800 6884200Mount Veld 455900 6807200Mount Windarra 425200 6848600Murrin Murrin 393200 6813700Niagara mining area 349700 6750100Norseman 384900 6437000Ogilvies 434000 6896700Ora Banda 313640 6637960The Patch 384900 6437000Paddington 340950 6626375Perseverance 368300 6807600Pioneer Dome 375300 6460400Pyke Well 417200 6786500Rockys Reward 273000 6923900Rowles Lagoon 295000 6631000Silver Swan 369400 6636900South Windarra 425800 6834700Spargoville 354900 6536000Teutonic Bore 318600 6856100Wallaby 432200 6808200White Eagle 263200 6748100White Lake 348000 6582000Wildara 293000 6879300Wiluna 223500 7055700Yandal 317300 6949900Yeelirrie 212300 6979200Yilgangi 419900 6707300Yundamindera Station 406200 6778200

8

REPORT 95GROENEW

ALD, RIGANTIEast Yilgarn 1:100 000 Geological Inform

ation Series—

an explanatory noteThe East Yilgarn 1:100 000 Geological Information Series databaseprovides seamless coverage of 154 000 km of the Eastern GoldfieldsGranite–Greenstone Terrane, Western Australia. This is based on 57published 1:100 000-scale geological maps, with completereinterpretation of regolith geology, and application of anew State-wide scheme of rock type classification.Spatial data for the observed geologyencompasses 90 000 polygons for outcropand regolith units, 13 500 structural lines,and 21 000 structural orientation points.Other data themes include interpretedsubsurface Precambrian geology, magneticdata, mines and mineral deposit localities andresource information, tenement distributionand status information, and pseudocolourimages derived from recent Landsat 7 TM data.

2

This Report is published in digital format(PDF) as part of a digital dataset on DVD.It is also available online at:www.doir.wa.gov.au/gswa/onlinepublications.Laser-printed copies can be ordered from theInformation Centre for the cost of printing andbinding.

Further details of geological publications and maps produced by theGeological Survey of Western Australia are available from:

Information CentreDepartment of Industry and Resources100 Plain StreetEast Perth, WA 6004Phone: (08) 9222 3459 Fax: (08) 9222 3444

www.doir.wa.gov.au/gswa/onlinepublications

geological information series — an explanatory …...1 east yilgarn 1:100 000 geological...

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