EXPLANATORYNOTES

SHEET SG 51-9 INTERNATIONAL INDEX

DEPARTMENT OF MINERALS AND ENERGY

GEOLOGICAL SURVEY OF WESTERN AUSTRALIA

WILUNA

SECOND EDITION

1:250 000 SHEETWESTERN AUSTRALIA

Further details of geological publications and maps produced by theGeological Survey of Western Australia can be obtained by contacting:

Information CentreDepartment of Minerals and Energy100 Plain StreetEast Perth WA 6004Phone: (08) 9222 3459 Fax: (08) 9222 3444www.dme.wa.gov.au

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GOVERNMENT OFWESTERN AUSTRALIA

1:250 000 GEOLOGICAL SERIES

WILUNAWESTERN AUSTRALIASECOND EDITION

SHEET SH 51-9 INTERNATIONAL INDEX

by

T. R. FARRELL

Perth, Western Australia 2001

GEOLOGICAL SURVEY OF WESTERN AUSTRALIA

1:250 000 GEOLOGICAL SERIES — EXPLANATORY NOTES

MINISTER FOR STATE DEVELOPMENT; TOURISM;

SMALL BUSINESS; GOLDFIELDS–ESPERANCE

The Hon. Clive Brown MLA

DIRECTOR GENERAL

L. C. Ranford

DIRECTOR, GEOLOGICAL SURVEY OF WESTERN AUSTRALIA

Tim Griffin

Copy editor: D. P. Reddy

REFERENCEThe recommended reference for this publication is:FARRELL, T. R., 2001, Wiluna, W.A. (2nd edition): Western Australia Geological Survey,

1:250 000 Geological Series Explanatory Notes, 28p.

ISSN 0729–3720

National Library of Australia Card Number and

ISBN 0 7307 5683 1

Grid references in this publication refer to the Australian Geodetic Datum 1984 (AGD84)

Printed by Haymarket Bureau, Perth, Western Australia

Copies available from:

Information Centre

Department of Minerals and Energy

100 Plain Street

EAST PERTH, WESTERN AUSTRALIA 6004

Telephone: (08) 9222 3459 Facsimile: (08) 9222 3444

www.dme.wa.gov.au

iii

CONTENTS

INTRODUCTION ............................................................................................................... 1

Physiography, climate, and vegetation ........................................................................... 1

Previous investigations ................................................................................................... 3

Nomenclature .................................................................................................................. 4

REGIONAL GEOLOGICAL SETTING ............................................................................ 4

PRECAMBRIAN GEOLOGY ............................................................................................ 6

Agnew–Wiluna greenstone belt ...................................................................................... 7

Merrie greenstone belt .................................................................................................... 8

Yandal greenstone belt .................................................................................................... 8

Dingo Range greenstone belt .......................................................................................... 9

Mount Fisher greenstone belt ......................................................................................... 9

Archaean Yilgarn Craton .............................................................................................. 10

Ultramafic rocks (Au, Aup, Aus, Aut, Aux) ............................................................... 10

Fine-grained mafic rocks (Ab, Aba, Abf, Abg, Abip, Abm, Abs, Aby) ...................... 10Medium- to coarse-grained mafic rocks (Aog, Aogf, Aogo) .................................... 11

Felsic volcanic and volcaniclastic rocks (Af, Afp, Afdp, Afi, Afs, Aft) ...................... 12

Sedimentary rocks (As, Asc, Asd, Ash, Ass, Ac, Aci) ................................................ 12

Metamorphic rocks (Alqf ) ....................................................................................... 13

Quartzofeldspathic gneiss (Anq, Angb) .................................................................... 13

Granitoid rocks (Ag, Agm, Agg, Aga, Agd, Agmh, Agdq, Ags, Agmp, Agb,

Agf, Agnq, Agzq, Agz) .............................................................................................. 14

Quartz veins (q) ........................................................................................................ 15

Palaeoproterozoic mafic dykes (#d) ............................................................................. 15

Palaeoproterozoic Yerrida Basin .................................................................................. 15

Yerrida Group .......................................................................................................... 15

Windplain Subgroup ............................................................................................ 16

Juderina Formation (#Yj, #Yjf, #Yjb) .............................................................. 16

Johnson Cairn Formation (#Yc) ...................................................................... 16

Mooloogool Subgroup ......................................................................................... 16

Thaduna Formation (#Yt) ................................................................................ 16

Killara Formation (#Yk, #Ykd, #Ykc, #Ykb) .................................................... 16

Maraloou Formation (#Ym) ............................................................................. 17

Palaeoproterozoic Earaheedy Basin .............................................................................. 17

Earaheedy Group ...................................................................................................... 17

Yelma Formation (#Ey) ....................................................................................... 17

Frere Formation (#Ef ) ......................................................................................... 17

Windidda Formation (#Ed) ................................................................................. 18

Chiall Formation (#Ecw) ..................................................................................... 18

iv

Unassigned Proterozoic sedimentary rocks (#s) .......................................................... 18

Structure ........................................................................................................................ 18

Metamorphism .............................................................................................................. 19

PALAEOZOIC GUNBARREL BASIN ............................................................................ 20

Permian Paterson Formation (Pa) ................................................................................. 20

CAINOZOIC GEOLOGY ................................................................................................. 20

ECONOMIC GEOLOGY ................................................................................................. 21

Gold ............................................................................................................................... 21

Nickel ............................................................................................................................ 21

Uranium ........................................................................................................................ 22

REFERENCES .................................................................................................................. 23

APPENDIX

Gazetteer of localities ........................................................................................................ 28

FIGURES

1. Regional geological setting of WILUNA .......................................................................... 2

2. Physiography and simplified Cainozoic geology of WILUNA ........................................ 3

3. Simplified geological map of WILUNA ........................................................................... 5

4. Grey-scale image of total magnetic intensity for WILUNA ............................................. 8

TABLE

1. Summary of the geological history of WILUNA .............................................................. 6

1

Explanatory notes on the Wiluna1:250 000 geological sheet,Western Australia (second edition)

by T. R. Farrell

INTRODUCTION

The WILUNA* 1:250 000 geological sheet (SG 51-9) covers an area in the north EasternGoldfields Province (Fig. 1) bounded by latitudes 26°00'S and 27°00'S, and longitudes120°00'E and 121°30'E. The map is named after the town of Wiluna†, in the western partof the sheet area.

Access to WILUNA is via the Kalgoorlie–Meekatharra road, which services the town ofWiluna, or the Wongawol Road, which joins the Gunbarrel Highway at Carnegie on theSTANLEY sheet to the northeast. There are also graded roads connecting Wiluna to Sandstoneand the Yeelirrie, Barwidgee, Granite Peak, Cunyu, and Jundee homesteads (Fig. 2). Stationtracks and numerous mineral exploration grid lines provide good access to most areasunderlain by greenstones, but access is difficult to areas underlain by Archaean granitoidrocks or Proterozoic rocks due to the scarcity of tracks.

The sheet area is sparsely populated. The only permanent settlements are the town ofWiluna, small aboriginal communities at Kukabubba and Ngangganawili, mining campsfor the Wiluna and Jundee–Nimary gold mines, and the pastoral stations of Lake Way,Lake Violet, and Millrose.

PHYSIOGRAPHY, CLIMATE, AND VEGETATION

WILUNA is typically flat to undulating, ranging in altitude from about 490 m AustralianHeight Datum (AHD) around Lake Way in the southwest, to more than 600 m in the west.The main physiographic features on WILUNA are the playa lake systems of Lake Way inthe southwest and Lake Ward in the north, an unnamed easterly trending saline drainagein the southeast, and dissected plateaus of Proterozoic rocks in the northeast and central-west (Finlayson Range; Fig. 2). Mount Alice West, in the Finlayson Range, is the highestpoint in the area at 640 m AHD.

Areas underlain by greenstones are characterized by low strike-ridges of resistant rocks,subdued hills with rubbly outcrop and ferruginous debris, and broad valleys covered insheetwash and alluvium. Areas underlain by granitoid rocks are dominated by extensivesandplains, with scattered outcrops and small breakaways in areas of recent erosion.Proterozoic units in the west and northeast are gently dipping and typically form steep-sided plateau remnants. Prominent scarps in the Finlayson Range, north and west of Wilunatownship, have relative reliefs of up to about 50 m.

* Capitalized names refer to standard 1:250 000 map sheets, unless otherwise indicated.† Australian Map Grid (AMG) coordinates of localities on WILUNA mentioned in the text are listed in the

Appendix.

2

The climate of the area is semi-arid to arid, with an average annual rainfall of approximately254 mm*. The rainfall tends to be sporadic and varies markedly from year to year. Thesummers are hot, with maximum temperatures commonly in excess of 40°C, whereas thewinters are cool to mild with occasional frosts and an average maximum temperature inJuly of 19°C.

Most of Wiluna falls within the Murchison Region of the Eremaean Botanical Province(Beard, 1990), except for the area underlain by Proterozoic rocks in the northeastern corner,which lies in the Gascoyne Region. The following description of the vegetation on WILUNA

is mainly from Beard (1990).

The Murchison and Gascoyne Regions are dominated by mulga (Acacia aneura) country.Vegetation on areas of alluvium and sheetwash is characterized by low mulga woodlandwith a variety of small shrubs (mainly Cassia and Eremophila species), and various grassesand ephemeral herbs. Small trees (including Eucalyptus camaldolensis and Casurina obesa)grow adjacent to the larger watercourses. The vegetation on areas of outcrop is typifiedby mulga scrub, with other less abundant Acacia species, and a variety of shrubs (includingEremophila and Cassia). Spinifex (Triodia basedowii) grassland, with scattered trees

* Climate data from Commonwealth Bureau of Meteorology website, 2001.

Figure 1. Regional geological setting of WILUNA (modified from Myers and Hocking, 1998)

Wiluna

Laverton

Leonora

YILGARN

CRATON

EaraheedyBasin

YerridaBasin

BryahBasin

DUKETONSIR SAMUEL

LEONORA LAVERTON

WILUNA

100 km

Greenstone

Granitoid and quartzofeldspathic gneiss

Fault

Town

TRF45 22.03.01

123°120°

26°

27°

28°

121°30'

Phanerozoiccover

3

30 km

TRF46 22.03.01

Homestead

Community

Road

Playa deposits

Sandplain deposits

Colluvium and sheetwash

Calcrete

Duricrust

Archaean greenstone and associated elluvium

Kukabubba

Jundee

LakeVioletWiluna

NgangganawiliCommunity

LakeWay

Mine

Town

Archaean granitoid rock and associated elluvium

LakeWay

MillroseJundee–Nimary

Wiluna

Cunyu

Mt AliceWest

Mt Fisher

FINLAYSON

RA

NG

E

Proterozoic rocks Prominent hill

26°00'121°3

0'

120°0

0'

27°00'

LakeWard

Figure 2. Physiography and simplified Cainozoic geology of WILUNA

(mainly marble gum, Eucalyptus gongylocarpa) and small shrubs, is present in areas coveredby sandplains. Salt-tolerant plants, including saltbush (Atriplex species), bluebush(Maireana species), and samphire (Halosarcia species), grow in open, low-lying areas aroundlake systems.

PREVIOUS INVESTIGATIONS

Most of the early work on WILUNA focused on the gold deposits around the town of Wiluna(Blatchford, 1899; Gibson, 1908; Montgomery, 1909; Talbot, 1920; Edwards, 1953).

4

Sofoulis and Mabbut (1963) presented the first regional geological account of the area,and this was followed by the first edition map and Notes for WILUNA by Elias and Bunting(1981, 1982). Extensive hydrogeological work was also carried out in the area surroundingWiluna (Ellis, 1954; Chapman, 1962; Morgan, 1962; Brookfield, 1963; Sanders, 1973).

The WILUNA 1:250 000 sheet was remapped at 1:100 000 scale in the 1990s by theGeological Survey of Western Australia (GSWA) and the Australian Geological SurveyOrganisation (AGSO). Three 1:100 000 maps — LAKE VIOLET (Stewart and Bastrakova,1997), BALLIMORE (Blake and Whitaker, 1996a), and SANDALWOOD (Blake and Whitaker,1996b) — were published by AGSO. The remaining three 1:100 000 maps — MILLROSE

(Farrell and Wyche, 1997), CUNYU (Adamides et al., 1998), and WILUNA (Langford and Liu,1997) — were published by GSWA. Descriptions of the geology of the individual 1:100 000sheets are presented in Stewart (1997), Adamides et al. (1998), Farrell and Wyche (1999),Langford et al. (2000), and Whitaker et al. (2000).

Published works on the mine geology and gold mineralization at Wiluna includeMcGoldrick (1990), Hagemann et al. (1992), Kent and Hagemann (1996), and Chanter et al.(1998). The geology of the Matilda gold deposits, in the Coles mining centre south ofWiluna, is described by Morgan and El-Raghy (1990). Descriptions of the goldmineralization and geology of the Jundee–Nimary deposits are presented in Phillips et al.(1998a, 1998b) and Byass and MacLean (1998), and the setting of the deposits and controlson mineralization are discussed by Vearncombe (1998, 2000). The geology of the MountFisher gold mine, in the southeastern part of WILUNA, is described by Powell et al. (1990).

Nickel mineralization in ultramafic rocks at Honeymoon Well is detailed in Donaldson andBromley (1981), Gole and Hill (1990), and Gole et al. (1996). Aspects of the geology andvolcanology of the ultramafic rocks are also discussed by Hill et al. (1990, 1995).

Ferguson (1998) presented a compilation of the mineral occurrences on WILUNA. Briefdescriptions of aspects of the geology, exploration, and mineralization of various small partsof the area, mainly in the greenstone belts, can also be found in open-file statutory mineralexploration reports held in the Department of Minerals and Energy’s library in Perth.

NOMENCLATURE

All greenstones on WILUNA have undergone low- to medium-grade metamorphism.However, primary textures are preserved in many cases, and it is commonly possible toidentify the parent rock. In view of this, igneous or sedimentary terminology has been usedwherever possible. Metamorphic rock names have only been used in areas where the rockshave been extensively recrystallized and the protolith is no longer clear.

The nomenclature of the igneous rocks largely follows the recommendations of theInternational Union of Geological Sciences (Le Maitre et al., 1989). Komatiite refers toultramafic rocks with a platy olivine-spinifex texture (cf. Arndt and Nisbet, 1982), and high-Mg basalt refers to mafic volcanic rocks with varioles or relict pyroxene-spinifex texture.

REGIONAL GEOLOGICAL SETTING

WILUNA covers an area of Archaean granite–greenstone terrain on the northeastern marginof the Yilgarn Craton (Fig. 1), and small areas of the Palaeoproterozoic Yerrida (Occhipintiet al., 1997) and Earaheedy Basins (Pirajno, 1999; Fig. 3). The granite–greenstone terrainconsists of elongate belts of deformed and metamorphosed volcano-sedimentary rocks, and

5

30 km

TRF47 11.04.01

Earaheedy Group

Mafic dyke

Fault

EARAHEEDY BASIN

YIL

GA

RN

C

RA

TO

N

YIL

GA

RN

C

RA

TO

N

Yerrida Group

Syenite

Granitoid rock, mainly monzogranite

Interleaved foliated granitoid and mafic rocks

Quartzofeldspathic gneiss dominant

Chert and banded iron-formation

Metamorphosed felsic rock dominant

Porphyritic dacite; metamorphosed

Intermediate volcanic rock; metamorphosed

Metamorphosed mafic rock dominant

Metamorphosed ultramafic rock dominant

Hornblende quartz monzonite andminor quartz diorite

Granitoid rock and quartzofeldspathic gneissin various proportions

Layered sequence of quartzofeldspathic gneiss,monzogranite, and metamorphosed mafic rock

Mixed sequence of metamorphosedsedimentary and felsic rocks

YERRIDA BASIN

Metasedimentary rock dominantProterozoic sedimentary rock, unassigned

Merriebelt

Yandalbelt

Agnew–Wiluna

belt

DingoRange

beltMountFisher

belt

26°00' 12

1°3

0'

12

0°0

0'

27°00'

Wiluna

Wiluna

Erraw

alla

Fault

Cunyu

Jundee

Jundee–Nimary

LakeViolet

Millrose

Mt Fisher

Town

Homestead

Mine

Figure 3. Simplified geological map of WILUNA

large intervening areas of granitoid rock and gneiss, both of which belong to the EasternGoldfields Province (Gee et al., 1981; Griffin, 1990). The Yerrida Basin contains ac. 2.2 – 1.9 Ga volcano-sedimentary succession that lies unconformably on Yilgarn Cratonbasement. The Earaheedy Basin succession comprises deformed, c. 1.85 – 1.8 Ga, shallow-marine and fluviodeltaic sedimentary rocks that are unconformable on both the YilgarnCraton and Yerrida Basin (Pirajno, 1999; Jones et al., 2001).

6

The Precambrian rocks are overlain in the east by Phanerozoic sedimentary rocks of theGunbarrel Basin, (formerly part of the Officer Basin; Hocking, 1994), scattered outliers ofwhich are present in the northeastern corner of WILUNA. Much of the bedrock geology isobscured by Cainozoic regolith.

A summary of the geological history of WILUNA is presented in Table 1.

PRECAMBRIAN GEOLOGY

Greenstone belts in the north Eastern Goldfields Province contain a wide range of rocks,including chert, banded iron-formation (BIF), clastic sedimentary rocks, and ultramafic tofelsic volcanic and volcaniclastic rocks (Fig. 3). There are also local areas of conglomeratethat postdate the main greenstone sequences, and late felsic to intermediate dykes and plugs.The greenstones were deposited between c. 2750 and c. 2660 Ma (Kent and Hagemann,1996; Nelson, 1997a,b, 1998), and deformed and metamorphosed at grades ranging fromprehnite–pumpellyite to amphibolite facies (Binns et al., 1976).

Table 1. Summary of the geological history of WILUNA

Age (Ma) Tectonic event

c. 2750–2700 Deposition of early greenstone succession in Agnew–Wiluna belt (and other

greenstone belts?)

2747 ± 11(a) Intrusion of granitoid precursor to quartzofeldspathic gneiss; northern end of

Yandal belt

D1 deformation: tight to isoclinal folding in gneisses; foliation in early

greenstones

c. 2700–2690 Deposition of greenstones

c. 2685–2655 D2 deformation: strong foliation parallel to granite–greenstone contact;

main phase of granitoid intrusion

c. 2670–2655 Felsic to intermediate volcanism in Yandal belt

2658 ± 2(a) Intrusion of post-D2 granitoid dyke into gneiss at northern end of Yandal belt

c. 2650–2635(b) Late-stage granitoids; syenite to diorite and low-Ca monzogranite

c. 2640(b) D3 deformation: north to northwesterly trending shear zones and upright

folds

D4 deformation: kink folds and crenulations

c. 2400 Intrusion of Palaeoproterozoic mafic dykes

c. 2200–1900 Deposition of Yerrida Group in a rift-related basin

c. 1850–1800 Deposition of Earaheedy Group in a passive-margin setting

?c. 290 Deposition of Paterson Formation

SOURCES: (a) AGSO, OZCRON database

(b) Nelson (1997b, 1998)

7

There are few published studies on the structural geology of the north Eastern GoldfieldsProvince (e.g. Platt et al., 1978; Eisenlohr, 1989; Hammond and Nisbet, 1992; Farrell, 1997;Vearncombe, 1998), and interpretation of the structure has been hampered by the poorexposure in the region. The following summary of the structure is based on work carriedout during 1:100 000-scale mapping on the DUKETON, SIR SAMUEL, and WILUNA 1:250 000sheets.

Four regional Archaean deformation events (D1–D

4) have been recognized in the north

Eastern Goldfields Province (Hammond and Nisbet, 1992; Farrell, 1997; Wyche and Farrell,2000). Evidence of an early deformation is locally preserved in c. 2750–2700 Ma gneissesadjacent to greenstones (Farrell, 1997), but the nature of this event is unclear. The seconddeformation coincided with a period of extensive granitoid intrusion at c. 2685–2655 Ma,and was followed by a later phase of granitoid magmatism after c. 2650 Ma, including asuite of alkaline rocks (Smithies and Champion, 1999). The granitoid rocks range incomposition from diorite to granite, but monzogranite is by far the most abundant rocktype. The third deformation event occurred at c. 2640 Ma within a broadly east–westcompressional regime and resulted in the development of major, north to northwesterlytrending shear zones and the regional foliation trends. This event was followed by late-stage crenulation and kinking of all earlier structures. Numerous faults and fracture zonescut across all Archaean structures. The faults correspond to prominent aeromagneticlineaments, and many are intruded by Proterozoic mafic–ultramafic dykes (Hallberg, 1987)or quartz veins.

There are five greenstone belts on WILUNA — the Agnew–Wiluna, Merrie, Yandal, DingoRange, and Mount Fisher belts (Griffin, 1990; Fig. 3) — as well as small rafts of greenstoneswithin the granitoids. All greenstones in the region are poorly exposed, and much of theinterpreted geology is based on data obtained from mineral exploration drilling programs,and regional-scale (400 m line-spacing) aeromagnetic surveys (Fig. 4).

AGNEW–WILUNA GREENSTONE BELT

The Agnew–Wiluna belt (Fig. 3) in the western part of WILUNA contains a metamorphosedsequence of ultramafic, mafic, and felsic volcanic, and sedimentary rocks, as well as youngerconglomerate (Jones Creek Conglomerate). Ultramafic rocks host major nickel deposits atPerseverance, Six Mile, and Mount Keith (all on SIR SAMUEL), and Honeymoon Well onWILUNA. Large gold deposits are present at Wiluna and Agnew (on LEONORA).

The section of the Agnew–Wiluna belt exposed on WILUNA can be divided into easternand western domains separated by the Erawalla Fault (Fig. 3; Hagemann et al., 1992;Langford et al., 2000). Strongly deformed metasedimentary rocks adjacent to the ErawallaFault may be equivalent to the Jones Creek Conglomerate on SIR SAMUEL (Durney, 1972;Marston and Travis, 1976; Marston, 1978; Liu et al., 1998). In the eastern domain,Hagemann et al. (1992) described a westerly younging stratigraphy around the Wilunamining centre, and Gole and Hill (1990) described a westerly younging stratigraphy nearHoneymoon Well. A correlation between the successions at Wiluna and Honeymoon Wellwas proposed by Liu et al. (1995). In their stratigraphy, the lowest preserved unit, whichconsists of basalt and gabbro, is overlain by a unit dominated by basalt, including bothhigh-Mg and tholeiitic basalt. Felsic volcanic and sedimentary rocks, and a regionalultramafic unit (Liu et al., 1995), overlie the basalt. The uppermost unit consists ofsedimentary and felsic volcanic rocks.

There is no readily identifiable stratigraphy in the western domain because the mafic-dominated succession is poorly exposed and possibly repeated by folding. However, the

8

local presence of BIF and the absence of thick ultramafic units suggest that the sequenceis not the same as that east of the Erawalla Fault.

The age of the Agnew–Wiluna belt is poorly constrained. The only published sensitivehigh-resolution ion microprobe (SHRIMP) U–Pb zircon date from the northern part is2749 ± 7 Ma for a microdiorite dyke from the Wiluna mine (Kent and Hagemann, 1996).This age is supported by a SHRIMP U–Pb zircon date of 2720 ± 14 Ma for a felsic volcanicunit from near the Rockys Reward mine on SIR SAMUEL (Nelson, 1997b), and by aconventional U–Pb zircon date of 2795 ± 38 Ma for a granophyric differentiate from alayered gabbro near Yakabindie (on SIR SAMUEL; Cooper and Dong, 1983).

MERRIE GREENSTONE BELT

The southern tip of the Merrie greenstone belt extends onto the northwestern corner ofWILUNA, east of Cunyu Homestead. Exposure of this belt is poor, and the only outcropsare of extremely weathered mafic rock. On NABBERU, to the north, the Merrie greenstonebelt contains a metamorphosed succession of basalt, subordinate gabbro, and ultramaficrock, and local felsic and sedimentary rocks (Adamides, 2000).

YANDAL GREENSTONE BELT

The Yandal greenstone belt (Fig. 3) in the central part of WILUNA contains a large volumeof felsic volcanic and volcaniclastic rocks. Although there are a number of thin komatiite

Figure 4. Grey-scale image of total magnetic intensity for WILUNA (400 m line spacing, data fromAGSO and GSWA, 1994)

30 kmTRF48 26.02.01

12

0°0

0'

27°00'

26°00' 121

°30

'

9

and high-Mg basalt units, the Yandal belt does not have the thick units of ultramafic rockthat characterize the Agnew–Wiluna belt, and there is no known economic nickelmineralization.

The Yandal belt contains several major gold deposits (Jundee–Nimary on WILUNA

and Bronzewing, Mount McClure, and Darlot on SIR SAMUEL) and numeroussmaller deposits, and remains an area of significant gold exploration activity (Phillips et al.,1998a).

Poor exposure and a scarcity of younging indicators hinder determination of a detailedstratigraphy for the part of the Yandal greenstone belt on WILUNA (Fig. 3). In the northernhalf of the sheet, the belt bifurcates into two arms separated by an extensive area ofgranitoid rocks and gneiss. Outcrop mapping and examination of numerousmineral exploration drillholes (Stewart and Bastrakova, 1997; Farrell and Wyche, 1999)have allowed the western arm of the belt to be divided into three main lithologicalpackages:• an eastern sequence dominated by mafic and ultramafic rocks, with locally abundant

felsic volcanic and subvolcanic rocks (the Middle Greenstone Sequence of Phillips et al.,1998a);

• a thick central sequence of felsic volcanic and sedimentary rocks (the Upper GreenstoneSequence of Phillips et al., 1998a);

• a thin western sequence of mafic and ultramafic rocks, and prominent chert and BIF(the Lower Greenstone Sequence of Phillips et al., 1998a).

Pillow lava structures in high-Mg basalt in the mafic–ultramafic-dominated eastern sequenceindicate younging to the west. This is supported by sedimentary structures in drillcore fromthe Jundee gold mine.

There are few published geochronological data from the Yandal greenstone belt. In thesouthern part of the belt, on SIR SAMUEL, a SHRIMP U–Pb zircon age of 2690 ± 6 Ma wasdetermined for a porphyritic rhyolite from the Spring Well complex, and an age of2702 ± 5 Ma for porphyritic rhyolite from the Darlot mine (Nelson, 1997b). In the northernpart of the belt on WILUNA, a SHRIMP U–Pb zircon age of 2669 ± 10 Ma was obtainedfor a dacite porphyry from within the central sequence near Camel Bore (Nelson, 1998).Post-mineralization dykes at Jundee and Mount McClure have SHRIMP U–Pb zircon datesof 2668–2656 Ma (Yeats et al., 1999).

DINGO RANGE GREENSTONE BELT

The Dingo Range greenstone belt, which extends onto the southeastern corner of WILUNA

(Fig. 3) from SIR SAMUEL, contains a metamorphosed mafic–ultramafic sequence with thininterbeds of chert and BIF, and minor amounts of felsic and clastic sedimentary rocks. Thinunits of tremolite–chlorite schist and strongly deformed felsic rock are abundant. The partof the Dingo Range greenstone belt on WILUNA is almost completely obscured by regolith.The age of the Dingo Range greenstone belt is unknown.

MOUNT FISHER GREENSTONE BELT

The Mount Fisher greenstone belt is poorly exposed in the southeastern corner of WILUNA.Little is known about this belt, but it may be related to the Dingo Range greenstone belt.There are sparse weathered outcrops of mafic, ultramafic, and felsic rocks, as well as thinunits of chert. The age of the belt is unknown.

10

ARCHAEAN YILGARN CRATON

Ultramafic rocks (Au, Aup, Aus, Aut, Aux)

Ultramafic rocks are widely distributed through the Agnew–Wiluna and Yandal greenstonebelts on WILUNA. However, in most cases, the rocks are poorly exposed and much of thesurface exposure has been affected by deep weathering, resulting in the formation of adistinctive light-brown, siliceous caprock (Czu). Ultramafic rocks are typically in thin,laterally extensive units or lenticular bodies.

Ultramafic rocks on WILUNA have been separated into five units: undivided metamorphosedultramafic rock (Au), metamorphosed peridotite (Aup), serpentinite (Aus), talc–chlorite schist(Aut), and metamorphosed pyroxenite (Aux). Minor ultramafic rock types not shownseparately include tremolite–chlorite schist, talc–carbonate schist, and serpentinized dunite.

Undivided metamorphosed ultramafic rock (Au) is used mainly to describe fine-grained,deeply weathered, deformed, and locally altered ultramafic rocks where the original rocktype could not be positively identified. Serpentinized peridotite (Aup) is a fine- to medium-grained, granular, weakly foliated rock with well-preserved cumulate textures. Olivinecrystals are pseudomorphed by serpentine-group minerals. Fine-grained aggregates ofmagnetite, plus one or more of talc, tremolite, and chlorite, occupy the intercumulus areas,which were probably filled originally by pyroxene and magnetite. A minor associated rocktype is serpentinized dunite. Massive serpentinized ultramafic rock (Aus), lackingidentifiable primary textures, outcrops on the western edge of the Agnew–Wiluna belt nearBridal Well. Metamorphosed pyroxenite (Aux) forms a small body within granitoid rockson the western side of the Yandal belt, south of the Wongawol road.

There are patchy exposures of strongly deformed talc–chlorite(–carbonate) schist (Aut) inhigh-strain zones in all three greenstone belts, particularly near granite–greenstone contacts.The rock is soft, well foliated, typically fine grained, and contains finely intergrown talcand chlorite, as well as minor amounts of carbonate and finely dispersed opaque minerals(probably magnetite).

Fine-grained mafic rocks (Ab, Aba, Abf, Abg, Abip, Abm, Abs, Aby)

Metamorphosed mafic rocks are a major component of the greenstone sequences on WILUNA.

Undivided, metamorphosed mafic rock (Ab) is common throughout the Agnew–Wiluna,Yandal, and Dingo Range greenstone belts. The unit includes deeply weathered and veryfine grained mafic rocks, as well as subordinate interleaved metamorphosed gabbro andthin interbeds of metamorphosed sedimentary rock. It also includes some areas ofmetamorphosed tholeiitic basalt and plagioclase-phyric basalt that are too small to be shownseparately.

Amphibolite (Aba) is the dominant mafic rock type in areas of higher metamorphic grade,and is common in greenstone enclaves within granitoid rocks and in the greenstonesequences close to the granite–greenstone contacts. Amphibolite (Aba) consists mainly ofacicular hornblende and plagioclase, and is typically well foliated with a strong lineationdefined by the alignment of hornblende. In the Dingo Range belt, amphibolite is commonlyinterleaved with metamorphosed gabbro and tremolite schist. Amphibolite (Aba) is also aminor component of quartzofeldspathic gneiss (Anq), and mixed units containing gneisses(Angb, Agnq). In gneisses, the amphibolite is typically fine to medium grained and layeredon a scale of 5–30 mm, according to variations in the abundance of dark-green hornblendeand plagioclase. The rocks also contain subordinate pale-green clinopyroxene (?diopside)

11

and quartz, plus accessory sphene, epidote, and iron oxides. There are lenses of amphibolite(Aba), up to 1 km long and 400 m wide, north of Deadwood Bore on the western edge ofWILUNA. These amphibolite bodies are interpreted as metamorphosed gabbro. The weakdeformation of the amphibolite lenses, and the presence of fine-grained margins andoffshoots into the surrounding strongly deformed granitoid rocks, suggests that they haveintruded the granitoids.

Strongly foliated metamorphosed mafic rock (Abf ) is common along the margins of theAgnew–Wiluna belt in the Coles Find* area. Also common in areas close to the granite–greenstone boundary is a mixed unit of strongly foliated mafic rock with abundantinterleaved, deformed granitoid rock (Abg).

Metamorphosed porphyritic basaltic andesite (Abip) is only encountered in explorationdrillholes in the northern part of the Yandal belt near Panakin Bore and in the Jundee area.The rock consists of albitized plagioclase phenocrysts set in a recrystallized matrix ofplagioclase and actinolite, with minor chlorite, biotite, and epidote.

Metamorphosed high-Mg basalt (Abm) includes basaltic volcanic rocks characterized bypyroxene-spinifex textures or varioles. The best exposure of high-Mg basalt is southeastof the Jundee–Nimary gold mine in the Yandal belt. Here, the rock has abundant variolesand a locally preserved relict pyroxene-spinifex texture, consisting of randomly orientedtremolite–actinolite pseudomorphs of igneous pyroxene set in a fine-grained matrix oftremolite–actinolite, chlorite, epidote, albite, and fine-grained opaque minerals. Locally,the rock contains pillow structures that indicate younging to the west (Farrell and Wyche,1999). The basalt is spatially associated with metamorphosed fine-grained gabbro.

Fine- to medium-grained, well-foliated, chlorite-rich mafic schist (Abs) is restricted to afew small outcrops in the Yandal belt north of Millrose Homestead, although it has alsobeen noted in drillholes in the Jundee area. The origin of this rock is unclear — it may bederived from mafic volcaniclastic rocks, high-Mg basalt, or ultramafic rocks.

Metamorphosed amygdaloidal basalt (Aby) is a minor mafic rock type in the Yandal belt.Amygdales are a common feature in the mafic volcanic rocks, but amygdaloidal basalt israrely in mappable units. The amygdales are up to 15 mm in size, and contain assemblagesof pale amphibole, subordinate albite, and minor amounts of epidote and sphene. The hostbasalt is typically fine grained and consists of quartz, plagioclase, epidote, and actinolite.

Medium- to coarse-grained mafic rocks (Aog, Aogf, Aogo)

Medium- to coarse-grained mafic rocks form intrusions or coarser intervals in mafic volcanicsuccessions. Metamorphosed gabbro (Aog) is common in all the greenstone belts on WILUNA,and also includes dolerite or microgabbro and areas of basalt with abundant gabbrointrusions. The primary minerals are pseudomorphed by metamorphic assemblages ofamphibole, plagioclase, and minor, fine-grained opaque minerals (?ilmenite), and localquartz. The rocks may be intergranular, granular, subophitic, or locally porphyritic. Stronglyfoliated metamorphosed gabbro (Aogf) is typical of areas adjacent to the granite–greenstonecontact, such as the Coles Find area.

Metamorphosed olivine gabbro (Aogo) is present in a small intrusive body near Twin TanksWell in the Yandal belt. The rock is fine to medium grained and undeformed, and containsclinopyroxene, plagioclase, a skeletal opaque mineral (?magnetite), and altered, anhedral

* Labelled as Coles mining centre on the 1:250 000 map sheet.

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?olivine up to 4 mm in size. The olivine is pseudomorphed by very fine fibrous chlorite,acicular tremolite, and fine-grained, granular epidote.

Felsic volcanic and volcaniclastic rocks (Af, Afp, Afdp, Afi, Afs, Aft)

Metamorphosed felsic rocks are common in the Yandal belt near Lake Violet Homestead,and in the northern end of the Agnew–Wiluna belt, but are only a minor component of theDingo Range belt. In most cases the felsic rocks are poorly exposed and affected by deepweathering.

Undivided metamorphosed felsic volcanic and volcaniclastic rocks (Af ) are typicallykaolinized and silicified. Relict quartz is common in hand specimen and assists in theidentification of the rocks. Deeply weathered felsic rocks have only been subdivided wherethey have a relict porphyritic texture (Afp).

Metamorphosed dacite porphyry (Afdp) is exposed in fresh, rubbly outcrops south of CamelBore in the Yandal belt (Farrell and Wyche, 1999). The rock is undeformed and seriatetextured to porphyritic. Plagioclase and quartz crystals, up to 16 mm in size, are set in afiner grained groundmass of quartz, plagioclase, and minor biotite, with metamorphic whitemica, chlorite, sphene, epidote, ?pumpellyite, and very fine iron oxides. The dacite porphyrycontains some scattered, irregular aggregates of chlorite and epidote, and clusters of?pumpellyite, which may be former amygdales. The rock has a SHRIMP U–Pb zircon dateof 2669 ± 10 Ma (Nelson, 1998).

Metamorphosed intermediate rocks (Afi) are a minor component of the greenstone sequencesin the Yandal belt. They range in composition from basaltic andesite to dacite. These rockstypically contain plagioclase phenocrysts (up to 6 mm), and altered mafic minerals in afine-grained groundmass of quartz and plagioclase, with small amounts of chlorite and ironoxides, and accessory zircon, apatite, and epidote. These rocks are interpreted to be dykesor shallow-level intrusions.

Strongly deformed felsic schist (Afs) is present in areas of higher metamorphic grade alongthe greenstone margins. The schist is typically well foliated and contains relict, partlyrecrystallized quartz grains in a foliated matrix of quartz, white mica, and plagioclase. Thenature of the protolith is unclear, but is thought to have been a felsic volcanic orvolcaniclastic rock.

Felsic tuff (Aft) in the Agnew–Wiluna belt includes eutaxitic tuff with euhedral relicts offeldspar pyroclasts up to 1 mm, and ignimbritic tuff with relict feldspar clasts and pumicelapilli up to 5 mm.

Sedimentary rocks (As, Asc, Asd, Ash, Ass, Ac, Aci)

Metamorphosed sedimentary rocks on WILUNA can be divided into two broad categoriesaccording to their composition and mode of deposition — metamorphosed clasticsedimentary rocks (As, Asc, Asd, Ash, Ass) and metamorphosed chemical sedimentary rocks(Ac, Aci).

Undivided metamorphosed clastic sedimentary rocks (As) are deeply weathered and poorlyexposed. They are a minor component of the greenstone sequences on WILUNA, and typicallyform thin units within volcanic successions, or more extensive units with a significantvolcaniclastic component. The sedimentary rocks are typically well foliated and difficultto classify due to deep weathering.

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Metamorphosed sandstones (Ass) in the Yandal belt are broadly felsic in composition,and contain subrounded to well-rounded clasts of quartz, plagioclase, and felsic rock, in afine-grained metamorphosed matrix. Metamorphosed polymictic conglomerate (Asc) is aminor component of the sedimentary successions in the Yandal belt near Strife Bore. Therock is weathered and contains large (up to 300 mm), well-rounded clasts of massive chert,felsic rock, and BIF in a fine-grained mafic matrix.

Metamorphosed fine-grained sedimentary rocks (Ash) include metashale and metasiltstone,and are poorly exposed and deeply weathered. Locally, they are thin bedded and, in freshdrillhole samples, consist of scattered, fine sand-sized clasts of quartz and plagioclase in avery fine grained matrix of metamorphic quartz, albite, white mica, and opaque minerals.Graphite-bearing varieties are present locally. Metamorphosed carbonate-rich sedimentaryrocks, dominantly metadolomite (Asd), outcrop in one area northwest of Abercromby Wellin the Agnew–Wiluna belt.

Metamorphosed chert (Ac) forms extensive strike ridges throughout the greenstonesequences, and is a minor but distinctive rock type that can be a useful local stratigraphicmarker. There is a range from finely layered chert through to green-grey and brown-greymassive chert. The layering is typically 1 to 30 mm thick, and defined by variations iniron oxide and silica content. Chert units commonly have well-developed mesoscale folding,and some are brecciated or cut by late-stage fractures.

Metamorphosed BIF (Aci) is restricted to the western side of the Yandal belt, and the westernside of the Agnew–Wiluna belt around Deep Bore. Rhythmic layering in the BIF is typicallyplanar and laterally continuous, and up to 4 mm thick. The layering comprises alternatingsilica-rich and iron-oxide-rich zones, and is locally magnetite bearing. On the western sideof the Yandal belt, the BIF is associated with a metamorphosed succession of ferruginouschert, clastic sedimentary rocks, and ultramafic rock.

Metamorphic rocks (Alqf )

Quartz–feldspar schist (Alqf ) is a strongly foliated felsic rock, probably derived from felsicvolcanic or volcaniclastic rocks. The rock is associated with felsic schist, adjacent to theErawalla Fault, east of Bridal Well.

Quartzofeldspathic gneiss (Anq, Angb)

Gneisses underlie large areas on WILUNA, but the rocks are poorly exposed, being coveredmainly by sandplain and Cainozoic sheetwash deposits. The quartzofeldspathic gneissesare multiply deformed and intruded by granitoids in many locations, and are older than alldated granitoid rocks. This is illustrated by a SHRIMP U–Pb zircon date of 2747 ± 11 Mafor a gneiss near the northern end of the Yandal belt (AGSO, OZCRON database), and therange of granitoid dates from 2658 to 2648 Ma (Nelson, 1998; AGSO, OZCRON database).

Quartzofeldspathic gneiss is present both as distinct, mappable units (Anq) and as acomponent of mixed units of granitoid rock and gneiss (Angb, Agnq, see Granitoid rocks).The rock commonly shows a diffuse layering defined by variations in grain size and modalmineralogy, and is multiply deformed. Locally, the gneiss contains two generations ofleucosomes and granitic veins. Early leucosomes are thin, rich in quartz, and parallel to arelict S

1 foliation. The leucosomes were folded during the D

2 event, and in high-strain zones

they are largely transposed in the S2 foliation. The first-generation leucosomes are cut by

a second generation of thicker, monzogranite leucosomes that are commonly subparallelto the S

2 foliation. Both the host gneiss and the early leucosomes are cut by an undeformed,

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porphyritic monzogranite dyke that has been dated at 2658 ± 2 Ma (AGSO, OZCRONdatabase).

A north-northwesterly trending belt in the central-northern part of WILUNA, at Amees Bore,contains a layered succession of quartzofeldspathic gneiss and metamorphosed hornblendemonzogranite, quartz monzonite, and mafic rock (Angb). The exposure is poor, butindividual layers appear to be less than 100 m thick. The monzogranite is a hornblende-bearing, fine- to medium-grained, well-foliated rock containing sparse clots of hornblendeup to 10 mm in diameter. There appears to be a gradation from hornblende monzograniteto hornblende-bearing quartz monzonite (Agzq, see Granitoid rocks). Numerous thin layers(less than 5 m thick) of mafic rock are also present. The main mafic rock type is a foliatedand lineated amphibolite (Aba, see Mafic rocks) with a crude layering defined by variationsin plagioclase content, and the alignment of thin, plagioclase-rich leucosomes. Epidotealteration of the succession is common and affects all rock types.

Granitoid rocks (Ag, Agm, Agg, Aga, Agd, Agmh, Agdq, Ags, Agmp, Agb, Agf, Agnq,Agzq, Agz)

Many areas of exposed granitoid rock are deeply weathered and have been mapped asundivided granitoid rock (Ag) if the primary mineralogy could not be ascertained. In areaswhere the rocks can be positively identified, biotite monzogranite (Agm) is by far thedominant rock type. Minor granitoid rocks types include granodiorite (Agg), fine-grainedaplitic granitoid (Aga), and dykes of diorite to quartz diorite (Agd). Hornblende-bearingmonzogranite (Agmh) and quartz diorite (Agdq) are only observed in drillhole samples. Abody of syenite (Ags) in the Yandal belt, west of Jundee Homestead, is not exposed, buthas been identified from exploration drillholes and aeromagnetic images.

Biotite monzogranite (Agm) is widespread on WILUNA. The rock is variously deformed andtypically fine to medium grained with local, sparsely porphyritic zones. The monzograniteconsists of quartz, plagioclase, K-feldspar, small amounts of biotite, opaque minerals, andaccessory epidote, allanite, sphene, and zircon. Porphyritic biotite monzogranite (Agmp)is present on the edge of the Yandal greenstone belt, near Millrose Homestead, and formsdykes in quartzofeldspathic gneiss east of Amees Bore.

Foliated granitoid rock with interleaved mafic rocks (Agb) outcrops along the eastern sideof the Agnew–Wiluna greenstone belt near Honeymoon Well. Aeromagnetic images suggestthat these rocks extend much farther north, in an area covered extensively by regolith. Themafic rocks typically form discontinuous layers or lenses in the granitoids, along with minoramounts of high-grade metasedimentary rock. Strongly deformed granitoid rock with minorquartzofeldspathic gneiss (Agf ) outcrops on the edge of the Agnew–Wiluna belt, nearHoneymoon Well, and north of Mount Wilkinson. Locally, the rock has biotite-richschlieren and a diffuse layering.

Over much of WILUNA, granitoid rocks are intimately associated with quartzofeldspathicgneiss and migmatite on a scale too small for the individual rock types to be shownseparately. Deep weathering and poor exposure also make it difficult to determine theproportions of each rock type, and so they are mapped as a mixed unit of granitoid rockand gneiss (Agnq). Granitoid rocks in this unit commonly have a diffuse layering andabundant biotite-rich schlieren.

There are several large bodies of quartz monzonite (Agzq) in the northern part of WILUNA.The quartz monzonite around Lake Ward is known only from mineral exploration drillholesand aeromagnetic data. The rock ranges in composition from monzogranite to quartz diorite

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and quartz monzonite. The dominant rock type is a weakly deformed, medium-grainedquartz monzonite containing equal proportions of plagioclase and K-feldspar, variousamounts of hornblende and clinopyroxene, and minor quartz and biotite. The quartzmonzonite east of Panakin Bore has been dated at 2664 ± 4 Ma (Nelson, 1999) on NABBERU,just north of WILUNA.

Quartz monzonite is also a component of the layered gneissic sequence near Lignan Welland at Amees Bore (Angb), where it appears to be in thin layers (less than 30 m thick).The monzonite in this sequence is a fine- to medium-grained rock containing K-feldspar,plagioclase, various amounts of quartz (5–20 vol.%), and minor sphene and myrmekite(after K-feldspar). Accessory minerals include iron oxides, apatite, epidote, and rare zircon.In contrast to the large bodies of quartz monzonite, the monzonite in the layered sequencedoes not contain clinopyroxene or biotite. Monzonite (Agz) has also been noted inexploration drillholes in parts of the Yandal belt.

Quartz veins (q)

Quartz veins (q) are ubiquitous on WILUNA, but in most cases are too small to be shown onthe map. Strongly deformed quartz veins are common in the greenstones. These veins aretypically subparallel to the regional foliation and boudinaged or folded. A younger set ofquartz veins, consisting of interlocking crystals of milky quartz and local iron oxides after?pyrite, cuts across the regional foliation trends and forms upstanding ridges in areas ofpoorly exposed granitoid rocks. These veins are typically east to northeasterly trending andparallel to linear magnetic features. Associated with these crosscutting quartz veins is aset of complex veins consisting of multiple generations of quartz veins, and variouslybrecciated and silicified wallrock.

PALAEOPROTEROZOIC MAFIC DYKES (#d)

Mafic dykes (#d) that cut across the granite–greenstone terrain on WILUNA belong to a suiteof Palaeoproterozoic mafic dykes found throughout the Yilgarn Craton (Hallberg, 1987).On WILUNA the dykes range in composition from gabbro to diorite or granophyric gabbro.They rarely outcrop, but are apparent on aeromagnetic images as distinct, linear anomalies(Fig. 4). Easterly trending mafic dykes outcrop between Granite Well and Terry Bore, eastof the town of Wiluna.

PALAEOPROTEROZOIC YERRIDA BASIN

Yerrida Group

Palaeoproterozoic sedimentary rocks of the 2.2 – 1.9 Ga Yerrida Group were deposited inthe Yerrida Basin, on the western border of WILUNA. The group has been divided into theWindplain and Mooloogool Subgroups (Occhipinti et al., 1997). The lowermost unit, theWindplain Subgroup, consists of sedimentary rocks deposited in fluvial and tidalenvironments in a continental sag basin (Occhipinti et al., 1997). The Mooloogool Subgroupcomprises basal turbidites and conglomerate, overlain by rift-related mafic volcanic andvolcaniclastic rocks, evaporites, and chemical sedimentary rocks.

On WILUNA the Windplain Subgroup is represented by the Juderina Formation, a siliciclasticunit with local stromatolitic carbonates and evaporites (Adamides et al., 1999; Langfordet al., 2000). The Mooloogool Subgroup is represented by the Killara Formation, which isa succession of subaqueous to subaerial lava flows and mafic sills, with local evaporitesand chemical sedimentary rocks (Adamides et al., 1999; Langford et al., 2000).

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Windplain Subgroup

Juderina Formation (#Yj, #Yjf, #Yjb)

The Juderina Formation (#Yj), at the base of the Yerrida Group, is a shallow-water sequenceof quartz sandstone with minor siltstone, chert breccia, and conglomerate. Two distinctivesubunits, the Finlayson and Bubble Well Members, have been recognized (Occhipinti et al.,1997). The formation outcrops around the margins of the Yerrida Basin, where it typicallyforms resistant ridges up to 60 m high.

The Finlayson Member (#Yjf ) is a unit of mature quartz sandstone and subordinate quartzsiltstone at the base of the Juderina Formation. The dominant rock type is an off-white,silica-cemented quartz sandstone with abundant ripple marks, and local brown diageneticspots. The sandstone is thin to thick bedded (a few centimetres to 1 m thick), and consistsof well-rounded quartz grains (0.2 – 0.5 mm in diameter) and minor detrital zircon,tourmaline, biotite, and rutile.

The Bubble Well Member (#Yjb; Gee and Grey, 1993) is a unit of chertified carbonateand evaporitic sedimentary rocks near the base of the Juderina Formation that is interpretedas a facies of the Juderina Formation (Adamides et al., 1999). The Bubble Well Memberhas both well-bedded and chaotic breccia facies. The unit typically consists of layers ofchert breccia, chert with a wavy microbial lamination, and chertified stromatolitic dolomite.An outcrop 2 km north of Top Kukabubba Well contains stromatolites of the speciesWilunella glengarrica (Grey, K., pers. comm. in Adamides et al., 1999).

Johnson Cairn Formation (#Yc)

The Johnson Cairn Formation (Occhipinti et al., 1997) is not exposed on WILUNA, but isinferred, from mapping on the GLENGARRY 1:100 000 sheet to the west, to underlie an areaon the western edge of WILUNA. In the type area, the formation consists of iron-rich shaleand minor carbonate.

Mooloogool Subgroup

Thaduna Formation (#Yt)

The Thaduna Formation (Occhipinti et al., 1997; originally named the ‘Thaduna Greywacke’by Gee, 1979) is not exposed on WILUNA, but is interpreted to underlie part of thenorthwestern edge of the sheet. The contact with the underlying Johnson Cairn Formationis inferred to be conformable (Bagas, 1998). The formation consists of lithic sandstoneand hematitic shale, and is interpreted as a proximal turbidite sequence (Occhipinti et al.,1997).

Killara Formation (#Yk, #Ykd, #Ykc, #Ykb)

The Killara Formation (#Yk; Occhipinti et al., 1997) consists mainly of dolerite and basalt,with local chertified microbial laminates near the top of the unit and is thought to be theresult of continental volcanism related to the rifting of the Yerrida Basin (Occhipinti et al.,1997). The Killara Formation interfingers with rocks of the Juderina and MaraloouFormations along the northeastern margin of the Yerrida Basin.

Dolerite sills belonging to the Killara Formation (#Ykd) have been preferentially intrudedalong siltstone layers at three different stratigraphic levels in the Juderina Formation

17

(Adamides et al., 1999). The dolerite consists of plagioclase, orthopyroxene, clinopyroxene(?augite), and magnetite, and has local interstitial granophyric intergrowths of quartz andfeldspar. The rock is microporphyritic in places.

Basalt of the Killara Formation (#Ykb) outcrops in an arcuate belt around the eastern edgeof the Yerrida Basin on WILUNA (Adamides et al., 1999). The basalt is fine grained andhas intergranular or intersertal textures. Microporphyritic varieties are developed in someareas. Clinopyroxene, plagioclase, and titanomagnetite, along with secondary chlorite,quartz, sphene, and prehnite, are the main constituents. There are thinner layers and chertyinterflow sedimentary rocks in the upper parts of the basalt.

The Bartle Member (#Ykc) is a thin, laterally discontinuous unit of chert, tuffaceous rocks,chertified sedimentary rocks, and thin lava flows (Occhipinti et al., 1997; Pirajno and Grey,1997). Deposition of the unit is interpreted to have occurred in a hot-spring environment(Pirajno and Grey, 1997). The unit consists largely of chert, and attains a maximumthickness of about 10 m. The chert is locally laminated, with cherty siltstone and ironstonein places. Bartle Member cherts locally contain silica pseudomorphs of rhomb-shapedcrystals (probably dolomite), globular iron-hydroxide structures, and spherulites ofchalcedonic silica (Adamides et al., 1999).

Maraloou Formation (#Ym)

The Maraloou Formation (Occhipinti et al., 1997) is not exposed on WILUNA, but has beeninferred to underlie part of the western edge of the area, based on mapping on theGLENGARRY 1:100 000 sheet. The Maraloou Formation consists of black shale, marl,dolostone, and minor chert.

PALAEOPROTEROZOIC EARAHEEDY BASIN

Earaheedy Group

Palaeoproterozoic rocks of the Earaheedy Group (Hall et al., 1977; Pirajno, 1999) areexposed in the northeastern corner of WILUNA. The four stratigraphically lowest formationsin the group are exposed in the sheet area, and the rocks are typically undeformed and dipgently to the northeast. The Earaheedy Group is interpreted to be a passive-marginsuccession deposited on the northern margin of the Yilgarn Craton at c. 1.85 – 1.8 Ga (Joneset al., 2000).

Yelma Formation (#Ey)

On WILUNA the Yelma Formation (#Ey) includes sandstone, shale, and minor conglomeratedeposited in shallow-marine and locally fluvial environments. The formation is only a fewmetres thick on WILUNA, but attains a maximum thickness of about 500 m on NABBERU tothe north (Hocking et al., 2000; Jones et al., 2000). Carbonate rocks that form part of theformation elsewhere (Hocking et al., 2000) are not present on WILUNA.

Frere Formation (#Ef)

The Frere Formation (#Ef ) consists of granular iron-formation (GIF), ferruginous siltstone,and shale, as well as minor BIF and chert. Granular iron-formation units consist of beds ofjasperoidal GIF, 50 to 200 mm thick, with intraclastic breccia and shale interbeds. IndividualGIF beds consist of iron oxides, peloids of microplaty hematite, chert, and jasper in a

18

chalcedonic or jasperoidal cement. Hematite is locally replaced by magnetite. The GIFunits probably formed on a continental shelf, where ferruginous peloids accreted in wave-and current-agitated, iron-rich, shallow waters (Beukes and Klein, 1992). Interbeddedferruginous shale and siltstone are parallel laminated with minor cross-laminations, andwere possibly deposited in a lagoonal environment.

Windidda Formation (#Ed)

The Windidda Formation (#Ed ) comprises limestone, shale, and minor jasper and GIF.The formation was probably deposited in a carbonate shelf with coastal lagoons. Recentmapping in the southeastern part of the Earaheedy Basin suggests that the WindiddaFormation is a correlative of the upper part of the Frere Formation, rather than an overlyingunit (Jones et al., 2000).

Chiall Formation (#Ecw)

On WILUNA the Chiall Formation is represented by the Wandiwarra Member (#Ecw;Hocking et al. 2000), which is a unit of siltstone and shale with subordinate sandstone thatoutcrops in the northeastern corner of the sheet area.

UNASSIGNED PROTEROZOIC SEDIMENTARY ROCKS (#s)

Proterozoic sedimentary rocks that have not formally been assigned to any stratigraphicunit outcrop at Mount Wilkinson, Mount Lawrence Wells, and near Scorpion Bore, eastof Wiluna town. The rocks at Mount Wilkinson and Mount Lawrence Wells consist of chertbreccia, quartz-vein breccia, siliceous arenite and conglomerate, cherty mudstone, andsilicified carbonates. These rocks are flat lying and undeformed, and partly overlain bysilcrete (Czz). They were correlated with the ‘Finlayson Sandstone’ (now the JuderinaFormation) by Elias and Bunting (1982), but have not been assigned to any stratigraphicunit in recent 1:100 000-scale mapping.

The unassigned sedimentary rocks east of the town of Wiluna consist of silicified quartz-rich arenite and conglomerate. They are restricted to several easterly trending ridges parallelto large quartz veins in the underlying granitoid rocks. Silicification of the sedimentaryrocks is considered to have occurred along fractures related to the formation of the quartzveins (Langford et al., 2000).

STRUCTURE

Four phases of Archaean deformation (D1–D

4) have been recognized in the north Eastern

Goldfields Province (Farrell, 1997; Wyche and Farrell, 2000) from regional 1:100 000-scale mapping carried out by GSWA and AGSO. The recognition of these structures isbased on overprinting relationships of outcrop-scale structures, interpretation of magneticimages, and correlation of structures in different parts of the area. All four phases ofdeformation are recognizable on WILUNA.

First-generation (D1) structures have largely been overprinted during later events, but relict

D1 fabrics are preserved in gneisses, and possibly in some greenstones. However, it is not

clear how the early structures in different parts of the area are related, or even if they aredue to the same event. Gneisses northeast of Turnup Bore, in the northwestern part ofWILUNA, commonly contain a composite S

1–S

2 fabric with rootless isoclinal folds of S

1

19

leucosomes. A SHRIMP U–Pb zircon age of 2747 ± 11 Ma (AGSO, OZCRON database)for a gneiss in this area constrains the timing of D

1 to c. 2750 Ma or later.

The second deformation (D2) coincided with peak metamorphism in the greenstones and

craton-wide granitic magmatism. The effects of D2 are recognized throughout the area, but

are most pronounced in high-strain zones in amphibolite-facies rocks adjacent to granite–greenstone contacts. This deformation may be equivalent to the early extension event (D

E)

of Hammond and Nisbet (1992).

The characteristic D2 structure is a steeply dipping foliation (S

2) subparallel to greenstone

margins. Layered cherts in the northern end of the Yandal belt contain a strong composite(S

0–S

2) fabric with abundant steeply plunging, tight to isoclinal, intrafolial folds (F

2). The

fold axes are typically subparallel to a prominent, steeply plunging, combined intersection– mineral lineation (L

2). Northeast of Turnup Bore, a 2747 ± 11 Ma gneiss contains F

2 folds

of S1 leucosomes. The gneiss is cut by an undeformed monzogranite dyke, parallel to S

2,

that has been dated at 2658 ± 2 Ma (AGSO, OZCRON database), indicating that D2 had

ceased by c. 2658 Ma.

The last major penetrative deformation event was largely responsible for shaping thepresent-day disposition of the greenstone belts. Strong east–west to east-northeast–west-southwest shortening produced large-scale, upright, and shallow to moderately plungingfolds, and north to northwesterly trending faults and shear zones (Fig. 3). Outcrop-scale F

3

folds are typically upright and open to tight with shallowly plunging axes that are subparallelto a fine mineral lineation (L

3).

The last recognized Archaean deformation in the region produced outcrop-scale kinks,crenulations, and quartz-filled tension-gash arrays. These features may be related to brittlefaults and fractures that form the high-angle conjugate structures described by Vearncombe(1998, 2000).

METAMORPHISM

All greenstones on WILUNA are metamorphosed. The greenstone belts show a distinctivemetamorphic zoning from amphibolite facies in areas close to granitoid contacts, togreenschist or prehnite–pumpellyite facies in the central parts of the belts. This type ofmetamorphic zonation is developed throughout the Eastern Goldfields Province (Binns et al.,1976), and is characteristic of Archaean granite–greenstone terrains worldwide (Condie,1981; Wilkins, 1997).

In the Agnew–Wiluna belt, the metamorphic conditions range from prehnite–pumpellyiteor lower greenschist facies in the centre of the belt (Hagemann et al., 1992) to amphibolitefacies in the south, near Coles Find and Honeymoon Well. At Wiluna the typical assemblagein mafic rocks is chlorite–epidote–quartz–plagioclase(–calcite). Hagemann et al. (1992) alsoreported the presence of pumpellyite in mafic rocks, but this is not diagnostic of prehnite–pumpellyite facies, as pumpellyite is also stable under lower greenschist-facies conditions.The absence of prehnite may be due to the presence of small amounts of CO

2 (indicated

by the presence of calcite), which is enough to suppress the formation of prehnite (Bucherand Frey, 1994).

In the Yandal belt, most of the greenstones are metamorphosed to lower greenschist (orprehnite–pumpellyite) facies. Amphibolite-facies rocks are restricted to narrow zones alonggranite–greenstone contacts. Mafic rocks in the centre of the belt contain the metamorphicassemblage chlorite–albite–epidote–actinolite, which is diagnostic of greenschist facies

20

(Bucher and Frey, 1994). Felsic rocks contain co-existing white mica – chlorite–albite(–epidote–pumpellyite), which indicates metamorphism at lower greenschist-faciesconditions (or lower).

In quartzofeldspathic gneisses, the assemblages are not diagnostic, but the presence ofCa-plagioclase is indicative of amphibolite-facies conditions (or higher). Additionally,the presence of clinopyroxene-bearing amphibolite lenses and localized partial meltingsuggest upper amphibolite-facies metamorphism and a peak temperature of more than650–700°C.

PALAEOZOIC GUNBARREL BASIN

PERMIAN PATERSON FORMATION (Pa)

Outliers of flat-lying, probable Permian sedimentary rock (Pa) are exposed in thenortheastern corner of WILUNA. These rocks are interpreted as part of the Paterson Formationon the basis of similarities with Permian rocks to the east (Lowry, 1971). The rocks consistof poorly sorted, medium- to coarse-grained sandstone, pebbly sandstone, and conglomerate.

CAINOZOIC GEOLOGY

Cainozoic regolith deposits, comprising residual indurated material exposed by erosion andyounger alluvial, eluvial, eolian, and lacustrine deposits, cover large areas on WILUNA.Individual regolith units have been mapped using field observations, aerial photography,and Landsat TM (Thematic Mapper) images.

The oldest regolith units typically form residual deposits on low hills and in breakaways,and are interpreted as remnants of the Tertiary weathering surface. These units includeferruginous duricrust and ferricrete (Czl), silcrete (Czz), and silica caprock over ultramaficrocks (Czu).

Proximal slope deposits, comprising rock debris, sand, and silt, lie on or adjacent to lowhills and on slopes beneath breakaways. They include colluvium (Czc), quartz-vein debris(Czcq), and ferruginous rock debris and ironstone rubble (Czf ). The latter unit forms bythe degradation of ferruginous duricrust, and is typically developed on low hills, and quartz-vein debris (Czcq) is typically associated with large quartz veins. Areas adjacent to outcropsof granitoid rock are commonly covered by deposits of coarse-grained quartz–feldspar sandwith various proportions of small fragments of granitoid rock (Czg).

Distal parts of the regolith are dominated by sheetwash (Cza) and sandplain deposits (Czs).Sheetwash deposits (Cza) are extensive adjacent to the main drainage systems and on themargins of sandplains. They consist of a thin layer of sand, silt, and clay over weatheredrock, and are gradational into sandplain deposits. Areas underlain by granitoid rocks arecovered by extensive sandplains (Czs) consisting of unconsolidated quartz sand and silt.Ridges of windblown sand are present locally.

The Lake Way drainage system in the southwest and the Lake Carnegie drainage in theeast contain a range of ephemeral lake deposits. Playa lakes (Czp) contain saline orgypsiferous evaporites, along with minor amounts of sand, silt, and clay. The playas areassociated with saline or gypsiferous dune deposits (Czd) that contain low, crescent-shapeddunes formed by wind action during dry periods. Extensive, low-lying areas containinghummocky deposits (Czb) of sand, silt, and clay, with small interspersed playas, claypans,

21

and patchy deposits of calcrete, surround the gypsiferous dune deposits. There are alsolarger deposits of calcrete (Czk) around the margins of the lake deposits.

Younger deposits of unconsolidated to semiconsolidated sandy alluvium and gravel (Qa),of probable Quaternary age lie along intermittently active fluvial channels and on adjacentfloodplains. These deposits grade laterally into sheetwash and may have undergone somedegree of eolian reworking. Lake and sheetwash deposits may also contain small claypans(Qac), consisting of thin deposits of silt and clay in shallow depressions that are filled withwater after heavy rainfall.

ECONOMIC GEOLOGY

Metallic mineral production from WILUNA is restricted to gold and accessory silver, withrecorded production to 30 June 2000 of about 161 882 kg of gold and 315 kg of silver.There are major deposits of nickel on WILUNA, although these have not yet been broughtinto production.

GOLD

WILUNA lies within the East Murchison Mineral Field, and includes five historic gold miningcentres — Wiluna in the southwest (Edwards, 1953; McGoldrick, 1990; Hagemann et al.,1992), and Coles Find (Morgan and El-Raghy, 1990), Kingston, Collavilla, and NewEngland in the south — as well as the disused Mount Fisher mine in the southeast (Powellet al., 1990), and the Jundee–Nimary mining operation in the central part (Byass andMacLean, 1998; Phillips et al., 1998b). Gold was discovered at Wiluna in 1896, and wasmined in three main periods (Chanter et al., 1998). Between 1896 and 1924, the gold wasextracted from near-surface reefs and relatively shallow workings into the oxidized zone(Gibson, 1908; Montgomery, 1909). Gold production fell when mining progressed belowthe oxidized zone and refractory, primary sulfide ore was encountered. The second mainperiod of mining occurred in the period 1926–1950, when sulfide flotation techniques wereused to treat the sulfide ore. Present-day mining operations commenced in 1984 (Chanteret al., 1998). Gold mineralization at Wiluna is in quartz–carbonate–fuchsite–sulfide veinsand breccia zones associated with late northerly to northeasterly trending faults (Hagemannet al., 1992). The mineralization has tentatively been dated at c. 2630 Ma, or later (Kentand Hagemann, 1996).

Gold mineralization was not discovered in the Jundee area until the mid-1980s. The Jundeeand Nimary deposits were discovered during drilling programs in 1990 and 1992respectively (Lewington, 1995; Wright and Herbison, 1995). Opencut mining commencedin 1995, and a total of 48.8 t of gold was produced from the Jundee–Nimary project until30 June 2000. The geology of the Jundee–Nimary goldfield is described in more detail inByass and Maclean (1998) and Phillips et al. (1998b). Gold mineralization is in variouslyoriented quartz–calcite–pyrite veins in late brittle structures (Phillips et al., 1998b), whichare cut by undeformed felsic dykes dated at 2656 ± 7 Ma (Yeats et al., 1999).

NICKEL

Nickel mineralization is developed in a thick, poorly exposed ultramafic unit at HoneymoonWell in the southwestern part of WILUNA (Donaldson and Bromley, 1981; Gole et al., 1996).The mineralization is known from extensive drilling and geophysical surveys. Nickel ispresent as disseminated sulfides in serpentinized olivine-rich cumulates, and as massivesulfides in spinifex-textured komatiite flows (Gole et al., 1996). Deposits have beenidentified at Hannibals, Harrier, Wedgetail, Corella, and Kingston, all in the southwestern

22

part of WILUNA, with resources (indicated and inferred) of sulfide and laterite mineralizationtotalling about 370 Mt at average grades of 0.8 – 0.9% Ni (Outokumpu Oyj, 2000). Minornickel mineralization is also developed in ultramafic rocks elsewhere on WILUNA (Ferguson,1998).

URANIUM

Uranium (carnotite) mineralization is developed in calcrete along two palaeodrainagesystems that discharge into Lake Way in the southwestern part of WILUNA. Three prospects— Hinkler Well, Centipede, and Lake Way — have been identified (Ferguson, 1998). Atthe Lake Way prospect, carnotite forms coatings on bedding planes of rock fragments inalluvial gravels, and on fractures in calcrete. The prospect contains a measured resourceestimated at 3.77 Mt of ore at 0.98 kg/t U

3O

8 (3695 t of contained metal; Ferguson, 1998).

23

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YEATS, C. J., McNAUGHTON, N. J., RUETTGAR, D., BATEMAN, R., GROVES, D. I., HARRIS,J. L., and KOHLER, E., 1999, Evidence for diachronous Archaean lode gold mineralization in theYilgarn Craton, Western Australia: a SHRIMP U–Pb study of intrusive rocks: Economic Geology,v. 94, p. 1259–1276.

28

Appendix

Gazetteer of localities

Locality AMG coordinatesEasting Northing

Abercromby Well 233000 7027400

Amees Bore 254100 7101900

Bridal Well (abd) 225600 7029300

Camel Bore 264700 7079600

Centipede U prospect 237600 7027400

Corella Ni prospect 240000 7022700

Cunyu Homestead (abd) 211400 7118400

Deadwood Bore 201900 7028200

Deep Bore (abd) 209200 7035900

Granite Well 261900 7046300

Hannibals Ni prospect 239800 7019400

Harrier Ni prospect 241500 7017000

Hinkler Well U prospect 220100 7024000

Honeymoon Well (abd) 243100 7022200

Jundee Homestead 265400 7083100

Jundee–Nimary gold mine 260000 7081000

Kingston Ni prospect 243400 7014700

Kukabubba community 223800 7084600

Lake Violet Homestead 267200 7062400

Lake Ward 271500 7088000

Lake Way Homestead 248300 7016800

Lake Way U prospect 237300 7043900

Lignan Well 293000 7100500

Matilda gold mine 222900 7037600

Millrose Homestead 295700 7078200

Mount Alice West 224700 7079200

Mount Fisher gold mine 349500 7029700

Mount Lawrence Wells 221800 7031900

Mount Wilkinson 218100 7032000

Ngangganawili community 231500 7050500

Panakin Bore 274300 7117000

Scorpion Bore 242000 7057100

Strife Bore (abd) 259000 7073700

Terry Bore 253300 7070200

Top Kukabubba Well 224900 7087600

Turnup Bore 254400 7097600

Twin Tanks Well (abd) 267100 7070300

Wedgetail Ni prospect 237000 7023700

Wiluna gold mine 225000 7051300

Wiluna town 223400 7055500

NOTE: abd: abandoned

Localities are specified by Australian Map Grid (AMG) coordinates, Zone 51, to

at least the nearest 100 m

BARROWISLAND

DAMPIER ROEBOURNE

1 2 3

5 6 7

ONSLOW YARRALOOLA PYRAMID

NINGALOO YANREY

12 9

EDMUND

14

MANDORA

NABBERU STANLEY

GUNANYA

MUNRO

LA GRANGE

BROOME

PENDER

McCLARTYHILLS

JOANNASPRING

SAHARA

RUNTON

MADLEY

HERBERT BROWNE

WARRI

MORRIS

URAL

PERCIVAL

DUMMER

CROSSLAND

CHARNLEY

QUOBBA MT PHILLIPS MTEGERTON

COLLIER

ROBINSONRANGESHARK

BAY-

EDEL

HOUTMANABROLHOS

DONGARA-

GERALDTON-

AJANA

YARINGABELELE

GLENGARRY

MURGOO

YALGOO KIRKALOCKA YOUANMI

SANDSTONE

KINGSTON ROBERT

12

7 8

43

13 14 15 16

10

6

2 4

MTELIZABETH

LANSDOWNE DIXONRANGE

MT RAMSAY GORDONDOWNS

HELENA

WILSON WEBB

RYAN MACDONALD

1

CAMBRIDGEGULF

ASHTON

MEDUSABANKS

MONTAGUESOUND

CAMDEN SOUNDPRINCE

12 10

16 13 14

5 6

9 10

5

9 10

14 15 16 13 14

42 3 4 3 4

8,

7 5 6 7 8

12 9 11 12 10 11

13 14 16

12 3 4

5,

COBB RAWLINSON

BENTLEY SCOTT

YOWALGA TALBOTCOOPER

SIRSAMUEL

THROSSELL WESTWOOD LENNIS WAIGEN

LEONORA LAVERTON RASON NEALE VERNON WANNA

5 6

12 9 10

13 15 16 13 14

1 2 3 4 1 2

1 2

PERENJORI NINGHAN BARLEE MENZIES

HILLRIVERMOORA BENCUBBIN

JACKSON

PERTH KELLER- SOUTHERNCROSSBERRIN

6 7 8 5

9 10 11 12

14 15 16

MINIGWAL PLUMRIDGE JUBILEE MASON

CUNDEELEESEEMORE LOONGANA

FORREST

ZANTHUS NARETHA MADURA EUCLA

7 8 5 6

11 12 9 10

15 16 13 14

PINJARRA CORRIGIN HYDEN LAKEJOHNSTON

NORSEMAN

COLLIE DUMBLE-YUNG

NEWDE-GATE

RAVENS-THORPE

ESPERANCE-

PEMBERTON- MT BREMERBAY

MONDRAINISLAND

IRWIN INLET

ALBANY

2 3 4 1 2

6 7 8 5

6,

12

10

BALLA-DONIA

CULVER BURN-ABBIE

NOONAERA

MALCOLM-CAPE ARID

3 4 1 2

SD 52

SE 52

SG 52SG 51

SH 52SH 50

SI 51SI 50

SG 49

LONDON-DERRY

114 o 120 o 126 o

32 o

28 o

24 o

20 o

16 o

5,9

15,

7, 11

DRYSDALE-

BARKER-

10, 14 11, 155, 9

BUSSELTON-

AUGUSTA

YAMPI

3

DERBY

7

LENNARDRIVER

8

BAH

12

NOONKAN-MTANDERSON

SE 51

11

SF 52

MT BANNER-MAN

13

CORNISH

1 2

LUCAS

14

BILLILUNA

STANSMORE

6

ANKETELL

2

PATERSONRANGE

6

DOWNSBALFOUR

9

MARBLEBAR

8

NULLAGINE

5

YARRIE

1

PORTHEDLAND-

ISLAND4

BEDOUT

TABLETOP

11

ROBERTSON

13

NEWMAN

16

TUREECREEK

15

WYLOO

10

MINILYA

16

WINNINGPOOL

KENNEDYRANGE

1

13

WOORAMEL

5

GLENBURGH

6

BULLEN

1

TRAINOR

2

PEAK HILL

8

CUE

15

WIDGIE-

14

BOOR-ABBIN

13

KAL-GOORLIE

9

MOOLTHA

SF 49

WESTERN AUSTRALIA

TRF44 22.03.01

REGENT-

-

11 12

ROY HILLMT BRUCE

SF 50

Second Edition

GEOLOGICAL MAPS

RUDALL

10

SF 51

SG 50BYRO

10

EDJUDINA

6 SH 51KURNALPI

10

LISSADELL

2

14

DUKETON

WILUNA

9

INDEX TO 1:250 000-SCALE

EXPLANATORYNOTES

SHEET SG 51-9 INTERNATIONAL INDEX

DEPARTMENT OF MINERALS AND ENERGY

GEOLOGICAL SURVEY OF WESTERN AUSTRALIA

WILUNA

SECOND EDITION

1:250 000 SHEETWESTERN AUSTRALIA

Further details of geological publications and maps produced by theGeological Survey of Western Australia can be obtained by contacting:

Information CentreDepartment of Minerals and Energy100 Plain StreetEast Perth WA 6004Phone: (08) 9222 3459 Fax: (08) 9222 3444www.dme.wa.gov.au

FAR

RE

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WIL

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GOVERNMENT OFWESTERN AUSTRALIA

1:250 000 GEOLOGICAL SERIES

LAKE

Gum

Cree

k

WARD

LindsayGordon

Lagoon

IvesCk

L A K E W A Y

PEAK

GRANITE

NgangganawiliAboriginalLand

WILUNA 2

MOUNT GREEN

MOUNT ALICE WEST

Yard

Yard

Yard

Jundee

Millrose

Lake Way

NgangganawiliCommunity

Ngangganawili

AboriginalLand

Kukabubba

Cunyu (disused)

Millrose

Lake Violet

LAKE

VIOLET

ROAD

JUNDEE MILLROSEROAD

MEEKATHARRA ROAD

WONGAWOL

ROAD

SANDS

TONE

WILUNA

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YEEL

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KALGOORLIE

CANN

ING

STOC

KRO

UTE

WILUNA

NORTHROAD

JUNDEEROAD

WILUNA

NORTH

ROAD

New Spring Homestead 27 km

ROAD

WILUNA

WONGAWOL

ROAD

GRANITE

PEAK

KALGOORLIEÊMEEKATHARRA ROAD

ROSE HILLS

TWIN HILLSYd

Jundee Mine Village

Yd

Yd

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kath

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158

km

Yeelirrie Homestead 37 km

Old

Gid

gee

Hom

este

ad 1

05 k

m

Yakabindie Homestead 68 km

(abd)(abd)

Millgool Outcamp

Millbillillie

Wiluna

546 m

546 m

538 m

549 m

571 m

579 m

592 m

574 m

617 m

640 m

604 m

541 m

525 m

500 m

610 m

555 m

509 m

553 m

609 m

588 m

WILUNA 25

WILUNA 27

NMF129

WILUNA 26

WILUNA 16

WILUNA 15

WILUNA 5

WILUNA 4

NMF130

G 53-12

G 53-10

G 53-6

G 53-4

G 53-5

NMF 131

G 53-8

BARE GRANITE HILL

PROMINENT HILL

WILUNA 1

WILUNA 11

WILUNA 14

WILUNA 3

WELLS

Exploration CampHoneymoon Well

Barwidgee Homestead 5 km

Granite Peak Homestead 42 km

Yelm

a Ho

mes

tead

41

km

Wonganoo Homestead 21 km

Yd

MOUNTALICE

MOUNT WAY

LAWRENCEMOUNT

MOUNT WILKINSON

MOUNT FISHER

MOUNT CLEAVER

Yard

Yard

Yard

Yard

Yard

Yard

Yard

Yard

Yard

Yard

Yard

Yard

Yard

Yard

Yard

Yard

Yard

YardYard

Yard

Yard

Yard

Yard

Yard

Yard

Yard

YardYard

Yard

Yard

F I N

L A

Y S

O N

R A N

G E

P

B

Jundee Soak

SwampDuck

T

T

T

LAKE WAY

Ts

W

W

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No 1 W

Dingo W

L A K E

LAKEURAMURDAH

V I O L E T

B

B (abd)

W

The Bore (abd)

W

Sk

B

W

T

(abd)

(PD)

2A Tank (PD)Old Cunyu WellHomestead Bore

Spinifex Bore

McMeakin Bore

No 4 Bore

No 3 Bore (abd)

Fyfe Well

Jungarra Soak

Jungarra Bore

No 2 Well

Top Kukabubba WellDingo Rockhole

Calcalong Rockhole

Bendys Bore

Mudjon Bore

Optimist Bore

Kukabubba No 2 Bore

Little Kukabubba Well (abd)

Taylor Bore (abd)

Cork Bore (abd)

Bucktin Well (abd)

Quadrios Bore (abd)

Della Bore (abd)

Ross Well (abd)

Phyllis Well

Goosie Bore (abd)

No 1 Bore

No 2 Bore (abd)

North Pool

Chantra Billie Bore

Camp Well

Baldy Well (abd)

Town WellsShed No 1 Bore

Shed No 1 Bore

Shed No 2 Bore

Shed No 3 BoreClinchs Bore

Shannons Dam Bore (abd)Scorpion Bore (abd)

Harvey Bore (abd)

Spinifex Bore (abd)

Morrissey Well Beau Bore (abd) Carry On Bore

Uramurdah Well (abd)

Warren Bore (abd) Sandhill Bore (abd)

Coolibah Bore (abd)

Camel Soak Sandhill Bore

Gladsome Bore

Tall Bore

Prospector Well

Abercromby Well

Salt Bore

Hinkler Well

Tullock Well (abd)

Honeymoon Well (abd)

Butcher Well

Kingston WellScotty Well

North Bore

Lake Way Well

Cross Road Bore

Middle Bore

Centipede BoreJust It BoreTony Bore

Reserve WellDawson Well

White Well

Deadwood Bore

Atkins Well (abd) Bridal Well (abd)

Deep Well (abd)Deep Bore (abd)

Little Diorite Well (abd)

Lanagan Bore (abd)

Critch Bore (PD)

Ward 1 Well (abd) Gold Tooth Well (abd)

Old Govt Well (abd)

Trennaman Well (abd)

Freshwater Well (abd)

Red Hill Well (abd)

Old Yard Well (abd)

Railway Well (abd)

Hayes Well (abd)Vincent Bore

Bubble Well (PD)

Jeffries Bore (abd) Cocksparrow Well (abd)

No 1 Well (abd)

No 48 Well Moonbria Well

No 47 Well

Parson Well

Corktree Well

Gunally WellBasset Well

Duffer Well

Irving Well (abd) Limestone Well (abd)

Conglomerate Bore

Mitchell Well

Scaddan Well

Leeman Well

Taffy Bore

MacNamara WellToohey Well

Sailor Jack Well

No 30 Bore

No 28 Bore

No 29 Bore

No 27 Bore

No 13 BoreNo 26 Bore

No 17 Bore

McKay Bore

Gabbagundi Bore

North East Bore

Orphan Well No 2 Bore

Bowman Well (abd)

Rennie Well

Sandalwood Bore

Kingsley Well

Slav Well

No 16 Bore

Kalamunda Bore

New Trial Well

Little Well

Rinaldi Well

South Homestead WellBuglio Well

25 Mile Bore

Double Hole Well (abd)

West Guy Well

Guy Well

21 Mile Well

Granite Well

Breakaway BoreGranite Well

Ironstone Well

Woolshed Well

Ram WellVause Well

Munn Well

Marconi Well (abd)Deep Well

Two Flats Well

Mahood Well

Roto Well

Pumpkin Well

The Strip Well

Spinifex Well

Bitter Well

Pope Well Daulby Well Lupton WellKenden Well

Old Shaft Well

14 Mile Well

Double Barrel Well

Outcamp Well

8 Mile Well

Dingbat Well

Coolup Bore

Kooyong WellTragedy Well (abd)

Pommy Well

Destiny Well Longreach Well

Shady Well

Rocky WellOutcamp Well

Melrose Well

Mandilla Well

Granite Well Paddy Well

Biddy Well

Sam Well (abd)

Bullock Well

Spinifex Well

May Queen Well

Herbert Bore

Boomer Bore

Emu Bore

New Bore

Towser Bore

Supply Well

Mona Vale Well

East Well

Black Cat Well

Divine Bore

Porcupine WellSandy Bore

Panakin Bore

4 Mile Bore

Bundle Well (abd) Mistake BoreAlex Well

Kerry Lyn Bore

George BoreMizina Well

Hughes BoreAmees Bore

Turnup Bore

Dingo Bore

Quartz Bore

Lignan Well

Knob Bore

Pizzetti Well

Jackys BoreBogada Bore

Bejinks Bore

Terry Bore

Strife Bore (abd)

Nimarry Bore

Option Bore

Camel Bore

Mundy Bore

Christmas Bore Snake Well

Old Camp Bore

Boas Bore

Bloodwood Bore

Depot Bore

McHugh WellSoak Creek Well

Lockhart Well

Emu Bore

Two Hills Bore

Quartz Well

Lucky Bore

Harry Hill Well

Gum Well (abd)

Ronnie Bore (abd)

Twin Tanks Well (abd)O'Keefe Well

Oasis Bore (abd)

Boundary Bore

Dingo Bore

Fergy Bore

Oxby BoreHegarty Bore

Sardine Bore (abd)

Jink Bore (abd)

New Market Bore Camel Well Thomas Bore

North Well

Bartlett Bore (abd)

Worthy Bore (abd)

Squeeky Bore (abd)

Johnson Bore

New Bore

Christmas Creek Well

Gravel Bore

Octopus Bore (abd)Desert Bore

Quartz Bore

Tommy Bore

Deep Well

Porcupine Bore

King BoreSpinifex Bore

Fyfe Bore

Running Waters BoreCorner Well

Lorna Glen Well

Karrah Bore

No 5 Bore

No 1 BoreNo 3 Bore No 2 Bore

No 4 Well (abd)

No 10 Well

No 2 Well

No 4 Bore

No 9 Well

No 1 Well84 Bore

65 Well (abd)

Two Hills Well (abd)

Plover Bore

WellMurphy

WH

S

Norms Bore

Spring

Bore (abd)

Bore

Bore (abd)Bore

Bore

Bore

MorphettWell

Well

Hadji Bore

Bore

Well (abd)

Well

WaterholeWaterhole

Soak

TipperaryWell

Springs

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Caledonian

Gunbarrel

Happy Jack

JundeeNimary

Rose Hills

Gourdis 81400Gourdis Laterite

Gourdis Main

VauseGourdis South

Capellis Find

WestLode East Lode

Lake Way

Maltilda

Centipede

Wedgetail

Corella

Hannibals

Harrier

Kingston

EnterpriseKingston

Pomme D'Or

Hinkler Well

Mount Fisher

Empire Laterites

Corboys Find

Bills Find

Sims Find

New Golden Way Slav Well

Herbert Well

Flushing Meadow

May QueenRewardIves Find

WILUNA

COLES

KINGSTON

COLLAVILLA

NEW ENGLAND

E A S T M U R C H I S O N M I N E R A L F I E L D

W I L U N A D I S T R I C T

M U R C H I S O N M. F.

Af

Au

Af

M E E K A T H A R R A D I S T

WILUNA

Happy Jack

Sims Find

Jundee

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15

22

PRODUCT OF THE NATIONAL

GEOSCIENCE MAPPING ACCORD

2 3

10

Kilometres

0 20 30 40 50

SCALE 1:1000 000

10

Kilometres

0 20 30 40 50

SCALE 1:1000 000

0 5 10 15 20 25 305000

Metres KilometresTRANSVERSE MERCATOR PROJECTION

VERTICAL DATUM: AUSTRALIAN HEIGHT DATUM

SCALE 1:Ý250Ý000

Grid lines indicate 20Ý000 metre interval of the Australian Map Grid Zone 51

HORIZONTAL DATUM: AUSTRALIAN GEODETIC DATUM 1984

ñg

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Alluvium _ clay, silt, sand, and gravel; in channels and on floodplainsClay and silt in claypans

Ephemeral lake and dune deposits _ clay, silt, and sand; in drainage basins adjacent to playa lakesDune deposits _ sand, silt, clay, gypsum, and carbonate; in low dunes adjacent to playa lakesPlaya deposits _ saline and gypsiferous evaporites, clay, and sand in playa lakes

Sheetwash deposits _ clay, silt, and sand in extensive fans; commonly ferruginousSandplain deposits _ unconsolidated sand and minor silt; includes stabilized dunes

Colluvium _ silt, sand, and rock debris as slope deposits and proximal sheetwash; includes ironstone fragmentsQuartz vein rubble and debris

Ferruginous rubble _ degraded lateritic duricrust, and ferruginous debrisSand over granitoid rock _ quartzofeldspathic sand

CalcreteLateritic duricrustSilica caprock over ultramafic rockSilcrete

sandstone, pebbly siltstone, and conglomerate

Conglomerate, quartz-rich sandstone, arkosic sandstone, and microbial laminates; commonly silicified and brecciated

siltstone and shale, and subordinate sandstone

limestone and shale

granular iron-formation, ferruginous siltstone, and shale; minor banded iron-formation and chert

sandstone, shale, and minor conglomerate

undivided mafic intrusive and extrusive rocks (simplified geology only)

chertified microbial laminates with barite and anhydrite nodules

Medium- to coarse-grained dolerite dykes and sills

Aphyric tholeiitic basalt

quartz sandstone; local siltstone, chert breccia, and conglomerate

stromatolitic chert and chert breccia; minor dolomite

quartz arenite and subordinate siltstone; planar-bedded or cross-stratified; commonly ripple-marked

Mafic dyke

Quartz vein

Syenite (simplified geology and subsurface)Monzonite (subsurface only)

Granitoid rock, undividedFine-grained granitoid rockFoliated granitoid rock with interleaved mafic rockDiorite and quartz dioriteQuartz diorite and quartz monzodiorite (subsurface only)Foliated granitoid rockGranodioriteBiotite monzograniteHornblende monzogranite (subsurface only)Porphyritic biotite monzogranite

Granitoid rock and quartzofeldspathic gneiss; minor calcÊsilicate gneiss and mafic gneissHornblende quartz monzonite; minor quartz diorite

Interlayered quartzofeldspathic gneiss, monzonite, and metamorphosed mafic rockQuartzofeldspathic gneiss, commonly with diffuse layering

QuartzÊfeldspar schist

Metamorphosed sedimentary rock, undivided; includes minor felsic volcaniclastic rockPolymictic conglomerate; metamorphosedDolomite; metamorphosedShale, and minor siltstone and sandstone; metamorphosedSandstone and minor siltstone; metamorphosed

Chert and banded chert; metamorphosedBanded iron-formation; metamorphosed

Metamorphosed felsic rock, undividedPorphyritic dacite; metamorphosedIntermediate volcanic rock; metamorphosedPorphyritic felsic rock; metamorphosedFelsic schistFelsic tuff; metamorphosed

MetagabbroStrongly foliated gabbro; metamorphosed

Olivine gabbro; metamorphosed

Metamorphosed fine- to medium-grained mafic rock, undivided; includes some metagabbroAmphibolite; generally fine- to medium-grainedStrongly foliated metamorphosed mafic rockStrongly foliated metamorphosed mafic rock interleaved with minor foliated granitoid rockPorphyritic basaltic andesite; metamorphosed (subsurface only)High-Mg basalt; commonly with pyroxene-spinifex and variolitic textures; metamorphosedMafic schist; chlorite-rich schist, probably after high-Mg basaltAmygdaloidal basalt; metamorphosed

Metamorphosed ultramafic rock, undividedPeridotite; metamorphosedSerpentinized ultramafic rockTalcÊchlorite(Êcarbonate) schistPyroxenite; metamorphosed

Bubble Well Member:

FRERE FORMATION:

WINDIDDA FORMATION:

YELMA FORMATION:

KILLARA FORMATION:

Bartle Member:

JUDERINA FORMATION:

Finlayson Member:

Geological boundary

exposed....................................................................................

concealed, interpreted from aeromagnetic data...................

Fault or shear zone

exposed....................................................................................

concealed, interpreted from aeromagnetic data...................

Bedding, showing strike and dip

Way-up indicator

pillow structure........................................................................

sedimentary structure.............................................................

inclined.....................................................................................

vertical......................................................................................

inclined.....................................................................................

horizontal..................................................................................

Mining area

Mineral occurrence

Nickel........................................................................................

Uranium....................................................................................

concealed.................................................................................

Metamorphic foliation, showing strike and dip

Joint, fracture, or vein, showing strike and dip

inclined.....................................................................................

vertical......................................................................................

prominent trend, unspecified.................................................

fracture pattern in granitoid rock...........................................

S-vergence...............................................................................

Mineral lineation, showing trend and plunge

tailings, mullock.......................................................................

inclined.....................................................................................

vertical......................................................................................

horizontal.................................................................................

Airphoto lineament

Small-scale fold axis, showing trend and plunge

trend of bedding.....................................................................

Archaean deformation

Structural symbols are labelled according to the sequence

DÛ, Dç..........................................................................

concealed.................................................................................

of local deformation events, where known

Strongly foliated rock............................................................................

Aeromagnetic lineament.......................................................................

Formed road..........................................................................................

Track.......................................................................................................

Railway, abandoned..............................................................................

Powerline................................................................................................

Landing ground.....................................................................................

Homestead.............................................................................................

Building..................................................................................................

Yard........................................................................................................

Microwave repeater station..................................................................

Horizontal control; minor......................................................................

Breakaway..............................................................................................

Sand dune..............................................................................................

Soak........................................................................................................

Spring......................................................................................................

Waterhole................................................................................................

Well.........................................................................................................

Pipeline...................................................................................................

Position doubtful....................................................................................

Abandoned.............................................................................................

Tank........................................................................................................

Windpump..............................................................................................

Bore.........................................................................................................

Mineral field boundary...........................................................................

Mining centre..........................................................................................

Mine (gold, unless otherwise indicated)..............................................

Major opencut........................................................................................

Opencut..................................................................................................

Treatment plant......................................................................................

made ground............................................................................

Mineral exploration drillhole, showing subsurface data.....................

Prospect ................................................................................................

crenulation, showing trend and plunge of axis, inclined.....

Intersection lineation, showing trend and plunge, inclined...............

unspecified...............................................................................

Watercourse with ephemeral pool, rockhole, soak,

spring or waterhole...................................................................

QUAT

ERNA

RY

CAIN

OZOI

C

PHAN

EROZ

OIC

PALA

EOZO

IC

PERM

IAN

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heed

y Gro

up

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loog

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ubgr

oup

Win

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in S

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oup

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da G

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PALA

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OTER

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C

PROT

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OIC

ARCH

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Y BA

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BASI

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YILG

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HEED

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N

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y Gr

oup

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Windp

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ubgr

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120^00À26^00À

15À

30À

45À

27^00À120^00À 30À 121^00À 121^30À

27^00À

45À

30À

15À

15À 30À 45À 121^00À121^30À15À

26^00À

15À15À 45À

GEOLOGICAL SURVEY OF WESTERN AUSTRALIA SHEET SG 51-9000 GEOLOGICAL SERIESAUSTRALIA 1:250

REFERENCE

JAMINDI

2647

THREE RIVERS

2747

MARYMIA

2847

FAIRBAIRN

2947

METHWIN

3047

RHODES

3147

MUDAN

3247

GLENAYLE

3347

KAHRBAN

3447

2642

2643

2644

2645

2646

2742

2743

2744

2745

2746

2842

2843

2844

2845

2846

2942

2943

2944

2945

2946

3042

3043

3044

3045

3046

3142

3143

3144

3145

3146

3242

3243

3244

3245

3246

3342

3343

3344

3345

3346

3442

3443

3444

3445

3446

WOODLEY

NOWTHANNA

GABANINTHA

GLENGARRY

BRYAH

SANDSTONE

YAGANOO

MOOLOOGOOL

DOOLGUNNA

MONTAGU

MEREWETHER

THADUNA

YEELIRRIE

WILUNA

CUNYU

MERRIE

MILLROSE

NABBERU

DARLOT

WANGGANNOO

SANDALWOOD

BALLIMORE

BANJAWARN

TATE

YELMA

WONGAWOL

EARAHEEDY

DUKETON

URAREY

COLLURABBIE

WINDIDDA CARNEGIE

COONABILDIE

MOUNT KEITH DE LA POER

COSMO NEWBERYSIR SAMUELDEPOT SPRINGSLAKE MASON

YOUNO DOWNS

MOUNT BARTLE

LEE STEEREGRANITE PEAK

VON TREUERLAKE VIOLET

PEAK HILL

SG 50-8

NABBERU

SG 51-5

STANLEY

SG 51-6

KINGSTON

SG 51-10

WILUNA

SG 51-9

GLENGARRY

SG 50-12

SANDSTONE

SG 50-16

SIR SAMUEL

SG 51-13

DUKETON

SG 51-14

Edited by N. Tetlaw and G. Loan

Cartography by D. Ladbrook and B. Williams

Topography from the Department of Land Administration Sheet SG 51-9with modifications from geological field survey

Published by the Geological Survey of Western Australia. Copies available fromthe Information Centre, Department of Minerals and Energy, 100 Plain Street,

East Perth, WA, 6004. Phone (08) 9222 3459, Fax (08) 9222 3444

This map is also available in digital form

Printed by the Sands Print Group, Western Australia

The recommended reference for this map is:FARRELL, T. R., 1999, Wiluna, W.A. Sheet SG 51-9 (2nd edition):Western Australia Geological Survey, 1:250000 Geological Series

Compiled by T. R. Farrell 1997

Geology after GSWA and AGSO maps (see sheet index)

15

70

35

80

39

75

SIMPLIFIED GEOLOGYSIMPLIFIED REGOLITH

N.T.

W.A.

S.A.

Qld

N.S.W.

A.C.T.

Vic.

Tas.

SHEET INDEX

Western Australia 1999

The lines indicate magnetic declination, 1995

+ means declination is east and correction must be

added to compass bearing to give true bearing

- means declination is west and correction must be

subtracted from compass bearing to give true bearing

Annual change is 1À easterly

NATURAL SCALE

Mafic dyke; dashes indicate concealed by younger rock

Quartz vein

SyeniteHornblende quartz monzonite and minor quartz diorite

Granitoid rock, mainly monzograniteInterleaved foliated granitoid and mafic rocks

Granitoid rock and quartzofeldspathic gneiss in various proportions

Layered sequence of quartzofeldspathic gneiss, monzogranite,and metamorphosed mafic rock

Quartzofeldspathic gneiss dominant

Metasedimentary rock dominantMixed sequence of metamorphosed sedimentary and felsic rocksChert and layered chert; metamorphosedBanded iron-formation; metamorphosed

Metamorphosed felsic rock dominantPorphyritic dacite; metamorphosedIntermediate volcanic rock; metamorphosed

Metamorphosed mafic rock dominant

Metagabbro

Metamorphosed ultramafic rock dominant

Paterson Formation

Proterozoic sedimentary rock, unassigned

Chiall Formation, Wandiwarra Member

Windidda Formation

Frere Formation

Yelma Formation

Maraloou Formation

Killara Formation

Bartle Member

Medium- to coarse-grained dolerite dykes and sills

Aphyric tholeiitic basalt

Thaduna Formation

Johnson Cairn Formation

Juderina Formation

Bubble Well Member

Finlayson Member

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Playa deposits

Sandplain depositsColluvium and sheetwash deposits

CalcreteDuricrust

Permian sedimentary rock

Proterozoic rock

Archaean granitoid rock and associated eluvium

Archaean greenstone and associated eluvium

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ìd

q

ñc

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ås000 maps shown in black1:100

Published 1:100000 maps used in compilation

See current GSWA map catalogue for full range of published products

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B C DA E

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10 km

SEA LEVEL

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10 km

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Wandiwarra Member:CHIALL FORMATION

DIAGRAMMATIC SECTIONS

PATERSON FORMATION:

SYMBOLS

000 maps shown in brown1:250

SHEET SG 51-9

SECOND EDITION 1999

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GEOLO

G IC A L SURVEY

WE

ST

E R N A U S T RA

LIA

GEOLOGICAL SURVEY OF

WESTERN AUSTRALIA

DAVID BLIGHT, DIRECTOR

DEPARTMENT OF MINERALS

AND ENERGY

L. C. RANFORD, DIRECTOR GENERAL

GOVERNMENT OF WESTERN AUSTRALIA

HON. NORMAN MOORE, M.L.C.

MINISTER FOR MINES

D

A

E

B

C