2010 annual group technical report mln 2 - mln 3 gemco mln ...€¦ · groote eylandt mining...
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2010 Annual Group Technical Report
MLN 2 - MLN 3
MLN 951 – MLN 953
MLN 956 – MLN 961
EMCO G
Version: 1.0
Replaces: N/A
Creation Date: 27 June 2010
Document Owner: Josh Harvey , GEMCO, Production Technical Lead (Geology)
Key Contacts: Josh Harvey, GEMCO, Production Technical Lead (Geology)
Adam Fritz, GEMCO, Superintendent (Technical Services)
Brief Description: Annual Report on Activities on Mining Leases for the reporting period.
BHP Billiton Manganese CSG/GEMCO 2010 Group Technical Report
EXECUTIVE SUMMARY
Groote Eylandt is Aboriginal-owned land, as granted under the Aboriginal Land Rights (NT) Act 1976. Groote Eylandt Mining Company Pty Ltd (GEMCO)’s obligations are chiefly embodied in various lease documents including Mineral Leases and Special Purpose Leases (SPLs), a Letter of Understanding dated 13 May 1965 and an Agreement dated 16 September 2006. Groote Eylandt is predominantly composed of a stable basement of Proterozoic quartz sandstones and quartzites. The overlying manganese deposits are part of a blanket of Cretaceous sediments lapping onto the western margin of the Proterozoic basement sandstones and quartzites of the McArthur Basin. The manganese orebody is a sedimentary layer, consisting of manganese strata occurring between clay and sand beds and gently undulates beneath the western plains of the island. It extends over an area of about 50 square kilometres as an almost continuous horizon ranging in thickness up to 11 metres. The ore body is thus essentially stratabound and strataform in character. The resource definition drilling program undertaken during FY10 (covering the period July 1 2009 to June 30 2010) year have been for the purpose of increasing confidence in the resource to measured category. A total of 1195 Reverse Circulation holes were drilled for a total of 33,203m in lease areas MLN951, 952, 953, 956, 957 and 959. 1051 holes intersected manganese. Aerial photography was carried out over all of the mining leases to facilitate annual reconciliations of stockpiles.
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Titleholder Groote Eylandt Mining Company
Operator (if different from above)
Tenement Manager/Agent Land Services - Nickelwest
Titles/Tenements MLN 2-3, 951-953, 956-961
Mine/Project Name GEMCO
Report title including type of report and reporting period including a date
2010 Annual Group Technical Report
Personal author(s) Josh Harvey
Corporate author(s) BHP Billiton GEMCO
Company reference number
Target Commodity or Commodities Manganese
Date of report 15 September 2010
Datum/Zone UTM Zone 53
250 000 K mapsheet BLUE MUD BAY
100 000 K mapsheet Bickerton
Contact details Postal address
Central Park 152-158, St George's Terrace, Perth
Fax
Phone +61862741334
Email for further technical details [email protected]
Email for expenditure [email protected]
REPORT DISTRIBUTION
Asset Leader – GEMCO 1 copy
Technical Services Superintendent – GEMCO 1 copy
Land Assist 1 copy
NT Department of Resources 1 copy
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CONFIDENTIALITY
All information contained in the report is confidential and disclosure of said information is subject to the BHP Billiton Anti-Trust Policy. None of this information should be publicly disclosed without the approval of BHP Billiton legal Advisors.
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Table of Contents
1.0 Introduction ......................................................................................... 6
1.1 Mine Description ................................................................................................. 7
1.2 Historical Background ......................................................................................... 7
1.3 Historical Ore Reserve Estimation ...................................................................... 7
2.0 Tenure .................................................................................................. 9
2.1 Land Status ......................................................................................................... 9
2.2 Tenements Involved............................................................................................ 9
3.0 Deposit geology................................................................................... 12
3.1 Geology Overview............................................................................................... 12
3.2 Stratigraphy......................................................................................................... 13
3.3 Manganese Ore .................................................................................................. 14
3.3.1 Primary Sedimentary Features ................................................................. 14
3.3.2 Secondary Manganese Enrichment.......................................................... 15
3.3.3 Mineralogy and Dominant Lithologies....................................................... 15
4.0 Drilling Programs ................................................................................ 17
4.1 Data types ........................................................................................................... 17
4.1.1 Drill hole database .................................................................................... 17
4.1.2 2009 Drill Program.................................................................................... 19
4.1.3 Drill Hole Inclusion in Resource Model ..................................................... 21
4.2 Sampling and analytical procedures ................................................................... 21
4.3 Quality control and quality assurance results ..................................................... 24
4.4 Physical parameters............................................................................................ 27
4.4.1 Density ...................................................................................................... 27
4.5 Aerial Survey....................................................................................................... 28
5.0 Appendices .......................................................................................... 29
5.1 Appendix A: 2010 Aerial Photography Data ...................................................... 29
5.2 Appendix B: Drilling Data ................................................................................... 29
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1.0 Introduction
The Groote Eylandt Mining Company Pty Limited (GEMCO) is owned by BHP Billiton (60%) and Anglo-American (40%) and has been mining manganese since 1964 in accordance with mining leases granted by the Commonwealth Government and traditional Aboriginal owners. The deposit is located in the Gulf of Carpentaria in the Northern Territory of Australia.
GEMCO Mine site
Figure 1 – Location
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1.1 Mine Description
Groote Eylandt is situated on the western side of the Gulf of Carpentaria approximately 50 kilometres offshore forming the eastern border of Arnhem Land. Groote Eylandt Mining Company (GEMCO) mines manganese from leases extending over an area of approximately 50 square kilometres on the western side of the island
Mining operations at GEMCO involves the removal of manganese ore by open-cut strip mining. The mining sequence is a continuous cycle; areas where ore has been extracted are backfilled with overburden from the next strip to be mined. This method results in the mining site moving across the orebody disturbing only a small section of land surface at any given time. The recovered manganese ore is then beneficiated to specified qualities at the mine site before being transported 16 kilometres north to the ship loading facilities at Milner Bay.
1.2 Historical Background
Between 1963 and 1967 BHP undertook an extensive exploration program on Groote Eylandt. The Groote Eylandt Mining Company was subsequently formed in December 1964 with special mining leases granted. In March 1966 the first shipment of manganese product was transported to the Tasmanian Electro Metallurgical Company (TEMCO).TEMCO produces ferro-alloys and manganese sinter.
In September 1966, the first export shipment was made to Japan. Two years later the beneficiation plant was designed and constructed to produce one million tonnes of lump ore per annum. During the mid 1980’s the concentrator was further upgraded to handle up to 2.3 MTPA. The burgeoning export market eventually saw annual shipments climb to at 2.19 million tonnes by 1990. FY08 was a record year with sales reaching a record high of 3.69 million dry product tonnes. The recently completed Groote Eylandt Expansion Project 1 (GEEP1) has increased the concentrator capacity to 4.0 million dry product tonnes per annum and further expansions are planned to further increase product sales.
1.3 Historical Ore Reserve Estimation
The history of ore reserve estimation is long and complex with various attempts and models been completed over the years. Previous estimations are summarised as follows:
Estimation Total resource (million dry ROM tonnes)
1975 FARAG & SLEE (published) 490 Mt
1985 Mining Mag.(published) 330 Mt.
1990 MINEX 189.9 Mt.
1993 MRT model 209.8 Mt.
1995 BHPE model 168.8. Mt
1995 BHP GEMCO model 149.2 Mt
1998 MINEX model 179.5 Mt
1998 BHP GEMCO model 138.8 Mt
1998 RUNGE model 227.6 Mt.
2000 (MAPTEK / SRK) GEMCO model 205.4 Mt
2000 estimation (2000 model) 205.4 Mt
2001 estimation (2000 model) 212.6 Mt
2002 estimation (2000 model) 209.6 Mt
2003 estimation (2000 model) 206.1 Mt
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2004 (Snowdens / Golders) GEMCO Model 153.35 Mt
2004 estimation (2004 model) 152.8 Mt
2005 estimation (2004 Model) 173.3 Mt *
2006 estimation (2004 Model) 169.4Mt
2007 estimation (2007 model) 169.6Mt
2008 estimation (2007 model) 163.4Mt
2009 estimation (2007 model) 159.8Mt
2010 estimation (2007 model) this estimation 155.2Mt
Table 1 – Estimation history
* The 2005 estimation is in dry ROM tonnes while the 2004 estimate reported dry in-situ tonnes. This change increased ROM tonnes while decreasing yields, leading to a slight reduction in product tonnes from FY2004 to FY2005.
The variability of the estimates over the years can be attributed to several factors. Aside from the impact of production, and the impact of the addition of drill holes to the data base there have been evolution of the resource / reserve reporting code as JORC code became emphasised in the group and also the changes in technology and estimation methodology and techniques, such as the use of Vulcan etc.
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2.0 Tenure
2.1 Land Status
Aboriginal Freehold Land - Anindilyakwa Land Council.
2.2 Tenements Involved
Groote Eylandt is Aboriginal owned land as granted under the Aboriginal Land Rights (NT) Act 1976. GEMCO’s obligations are chiefly embodied in various lease documents including Mineral Leases and Special Purpose Leases, a Letter of Understanding dated 13 May 1965 and an Agreement dated 16 September 2006. These documents cover Mining operations, the township, welfare of the Traditional owners, the Eastern Areas and other aspects ancillary to the Company’s operations.
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FIGURE 2 – Tenement Map
The associated GEMCO lease numbers and conditions are listed hereunder.
Lease No. # Area (ha) Activity Expiry Date
MLN 951 1,155 Mining & associated activities 16/09/2031
MLN 952 645 Mining & associated activities 16/09/2031
MLN 953 1,506 Mining & associated activities 16/09/2031
MLN 956 1,208 Mining & associated activities 16/09/2031
MLN 957 176 Mining & associated activities 16/09/2031
MLN 958 686 Mining & associated activities 16/09/2031
MLN 959 2,114 Mining & associated activities 16/09/2031
MLN 960 567 Mining & associated activities 16/09/2031
MLN 961 345 Mining & associated activities 16/09/2031
MLN 2 1.38 Power line lease 29/9/1989*
MLN 3 1.65 Bridge lease 24/7/1985*
Table 2 – Tenement list
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Applications have also been made for a number of exploration licences. Of these, 6 have been granted covering the so called Eastern Leases and offshore leases as well as offshore leases surrounding Groote Eylandt.
All of the on Eylandt exploration license applications cover Aboriginal land held under the ALRA.
EL Location
10108 Groote Eylandt (eastern areas) granted in 2001
10115 Groote Eylandt (eastern areas) granted in 2001
27576 Offshore Groote Eylandt granted 13 July 2010
27577 Offshore Groote Eylandt granted 13 July 2010
27578 Offshore Groote Eylandt granted 13 July 2010
27579 Offshore Groote Eylandt granted 13 July 2010
Table 3 – Exploration leases
Special Purpose Leases have been issued to GEMCO under the Crown Lands Act and Regulations covering the Township, Industrial area and Wharf facilities.
Special Purpose Lease No. # Area (ha) Activity Expiry Date
SPL (Por. 1302, 1307)
(Vol. 141, Fol.4) 7.52 Cargo handling wharf ancillary purposes 29/5/2065
SPL 383 (Por 1031, 1306)
(Vol. 141, Fol.7) 51.19 Industrial area including stockpiling of ore 29/5/2065
SPL 392 (Por. 1478)
(Vol. 141, Fol.5) 109.60 Township lease 29/5/2065
SPL 393 (Por.1479)
(Vol. 141, Fol.6) 89.87 Greenbelt around township 29/5/2065
Table 4 – Special Purpose leases
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3.0 Deposit geology
3.1 Geology Overview
The geology and mineralogy of the Groote Eylandt manganese deposits are well documented in the public record. Various sources have been drawn upon to briefly summarise the current knowledge of the Groote Eylandt deposits.
Groote Eylandt is predominantly composed of a stable basement of Proterozoic sandstones and quartzites. The manganese deposits are part of a blanket of Cretaceous sediments lapping onto the western margin of the Proterozoic basement sandstones and quartzites. Erosion channels in the basement have influenced both primary manganese deposition as sediments as well as supergene enrichment by laterisation.
The manganese orebody is a sedimentary layer, consisting of manganese strata occurring between clay and sand beds and gently undulates beneath the western plains of the island. It extends over an area of about 50 square kilometres as an almost continuous horizon ranging in thickness up to 11 metres. The ore body is thus essentially stratabound and strataform in character.
The orebody consists of pisolitic and oolitic manganese oxides. These oxides are thought to have originally been deposited as a chemical precipitate, forming a tabular sedimentary deposit in wave affected shallow sea-floor environments during a period of rising and falling sea levels. Subsequent to deposition, the manganese layer emerged from the sea during a worldwide drop in sea level. The depositional events were followed by a long period of tropical weathering, which extensively modified the upper parts of the sediment profile. Pisolitic manganese oxides underwent partial to complete remobilisation and recrystallisation that resulted in the formation of hard cemented pisolite and massive manganese oxides. The overlying clays and gravels were strongly oxidised and leached to form the iron and alumina rich laterites that are now removed as overburden.
Figure 3 shows the geological distribution of manganese ore on Groote Eylandt. Figure 4, diagrammatically depicts rock types, mining horizon and the relationship to the stratigraphic model.
The ore horizon is covered by laterite overburden ranging in thickness up to 25m. In most current areas, the overburden averages 5m thick. The orebody is typically mined as two different layers:
Middle - massive high grade ore and cemented and loose high-grade pisolitic ore.
Bottom - massive, high silica ore.
In the present mining areas, the mined ore horizon is between 0.5 and 11 metres thick. Currently a maximum of about twenty metres of overburden is being stripped using an Hitachi 2500 excavator (example F3, D, A South, E South and B quarry). Dozers have been effectively employed in pre-stripping since 1995 in some of the shallower quarries where lateritic clay overburden is between 0-15m thick (example F3N, parts of F3, C, F1 and the north east corner of D quarry). Currently mining is being carried out in B, E, F and A series Quarries with ROM product being extracted from G quarry.
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NGroote Eylandt
0 10 20km
North PointIsland
North East Isles
Cape Beatrice
South Point
WinchelseaIsland
Northwest Bay
Gulf ofCarpentaria
Dalumba Bay
Marangula Bay
Mud CodBay
AlyangulaAlyangula
AnguruguAngurugu
UmbakumbaUmbakumba
Sand dunes, ancient andrecent, calcareous in places
Alluvium, laterite, lateriticsoil, ferruginous gravel
Manganese oxides
Massive quartz sandstone,cross bedded, pebbly inplaces
Recent
Recent Mid Cretaceous
Mid Cretaceous
Mid Proterozoic
Port Langdon
Figure 3 – Geological setting
3.2 Stratigraphy
The Groote Eylandt stratigraphic sequence is as follows in chronological order:
Middle Proterozoic Basement (approx. 1800 Million Years)
Quartzite: A strongly jointed, massive, near horizontal unit.
Lower Cretaceous Sediment Sequence (approx. 136 Million Years)
Quartz Sandstone: Derived from the underlying older Proterozoic quartzite and does not contain fossils.
Glauconitic Sands and Clays: A succession of shallow marine sediments of clays, siltstones and sands. The upper part of the sequence hosts the manganese ore, which occurs in distinct strata. These strataform bodies form an integral part of the sedimentary sequence. The known extent of the manganese oxide deposit is over 20 kilometres in the north south direction. It is open on the western (seaside) and lenses onto and abuts hills of the quartzite basement to the east. Boundaries between sediment types tend to be vertically gradational, although sharp boundaries exist. Substantial sediment overlay the basement, although in places the manganiferous horizons may be in direct contact with the basement.
Tertiary Laterite and Clay (3 to 65 Million Years).
Deep tropical weathering has resulted in the development of thick laterite profiles, consisting of enrichment and depletion of hydrated iron oxides and clays. Both the glauconitic units, including the manganiferous rich horizons and overlying gravels and clays are lateritised.
Quaternary Soil (present to 3 Million Years)
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Soil - Red-brown topsoil forms a thin coverage typically centimetres thick, pockets up to 2-3 meters thick exist.
Figure 4 illustrates a typical lithological column and the relationship to the stratigraphic model of the Palaeo-Proterozoic to recent.
Figure 4 – Stratigraphic profile
3.3 Manganese Ore
The manganiferous deposits have largely resulted from the chemical precipitation of sedimentary iron, alumina and manganese minerals. There are two types of mineralisation, primary and secondary.
3.3.1 Primary Sedimentary Features
Whilst there is no clear evidence to indicate whether the primary manganiferous rich sediments are of organic or inorganic origin, characteristics of both deposits appear to be present within the Groote Eylandt mineralised resource. Oswald J (1990) has postulated an organic genesis for the manganiferous pisolites, suggesting the formation may be a phenomenon of coastal waters, river estuaries, lakes and embayments during a transgression of a stratified metal-enriched sea. An alternative is to consider an inorganic genesis of the pisolites, in which near shore and beach conditions (eg. wave action, long shore drift and winnowing) has strongly affected deposition.
The nature and form of these two potential origins may be significant in terms of modelling. Those areas along the original palaeo-coastline may represent the well-sorted sequence dominated by elongated bars of pisolites and oolites with ribbon like thickening. Whereas in other areas the
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mineralised strata has formed a blanket cover of shallow embayed zones and deeply filled channels of the palaeo-drainage, with the thickness and form of the layers strongly controlled by the direction and slope of the drainage system.
Mining has exposed primary sedimentary features that suggest a shallow marine environment. The ore contains pisoliths and ooliths, which is evidence of wave action influenced accretion. Inverse and normal graded bedding, cross bedding and ripple marks are evident, indicating deposition during a minor change from marine transgression to regression. In primary ore, manganese pisolites are loosely embedded in a matrix of white kaolin clay with very minor quartz sand. The primary ore is believed to be most closely represented by loose mangan pisolite and loose mangan oolite.
3.3.2 Secondary Manganese Enrichment
Lateritisation has mobilised manganese, iron, alumina and silica in the vertical profile. Manganese oxides through deep tropical weathering, during the Tertiary period have progressively replaced the kaolin matrix in the loose pisolite. This has caused the development of moderately thick laterite profiles above the ore. Diagenetic and supergene processes have recrystallised the primary manganese oxide minerals in the loose pisolite (pyrolusite, romanechite, todorokite, vanadates, lithiophorite, all with kaolinite gangue) to cemented mangan pisolite and massive mangite (dense cryptomelane and pyrolusite) at the top of the pisolitic ore and at the bottom of the siliceous faces.
The area has been extensively lateritised. In the wet season leaching of rocks occurs and in dry season the solution containing the leached ions is drawn to the surface by capillary action to be evaporated leaving salts to be washed away. Na, K, Ca, Mg are readily depleted and this can result in a complex vertical and lateral distribution of chemical environments. Specifically a solution containing these ions under suitable pH conditions can dissolve silica, leaving a clay saprolite. Sequences of smectite clay occur locally over the ore horizons - especially near F1 and C Quarry and regionally north from D quarry to B deposit and A South.
3.3.3 Mineralogy and Dominant Lithologies
The major sedimentary facies influencing ore types were pisolite facies and siliceous facies and these have been overprinted by supergene enrichment processes creating a supergene enriched facies.
Pisolite facies
Major mineable ore type
Generally confined to palaeo sea floor terraces close to palaeo highs
Thickest ore on terraces
Can be massive, cemented or loose pisolite/oolite
Pisolite is composed of pisoliths (> = 2mm diameter)
Oolite is composed of ooliths (< 2mm diameter)
Found stratigraphically above siliceous facies.
The supergene enriched facies can be sub-divided into three main types:
Massive Mangite - massive textureless manganese oxides usually occurring as a thin layer capping the orebody; formed by secondary recrystallisation and enrichment of primary pisolite ores.
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Cemented Mangan - Pisolite - primary pisolitic manganese oxides strongly cemented by a matrix of secondary manganese oxides; usually occurring in the upper part of orebody. The principle source of Metallurgical Lump ore.
Loose Mangan - Pisolite - primary pisolitic manganese oxides weakly cemented by a matrix of clay; predominantly kaolinite.
Siliceous facies
Most widespread manganese mineralisation on lease area is siliceous massive mangite.
Present as thin bands and disseminations dispersed in clays and sands.
Ore mineralogy consists of massive cryptomelane and pyrolusite with abundant quartz sand inclusions.
Formed when supergene processes during laterisation transported Mn (probably from overlying pisolitic facies) to lower stratigraphic levels.
Lowest stratigraphic manganese ore type - “bottom” horizon. Can rarely occur as thin mineralisation “cap”.
The mineralogy and chemistry of the ore is well described in Leenders’ Volume 1 of “Groote Eylandt Manganese Deposit – July 1995 Resources, pages 12-14.
The geological layers in the model have been classified according to a scheme that may be summarised as follows.
Stratigraphic layer SLAYER Code Zone
Soil layer 100 Overburden
Laterite and lateritic clay 200 Overburden
Concretionary Mn 300 Overburden
Massive Mangite Layer 400 Mid
Cemented pisolites and oolites 500 Mid
Loose Pisolites 600 Mid
Ferruginous pisolites and oolites 700 Bot
Siliceous mangite 800 Bot
Disseminated Mn 900 Underburden
Glauconitic sands and clay 1000 Underburden
Basement quartzites and sand 1100 Underburden
Table 5 – Stratigraphic layer classification
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4.0 Drilling Programs Numerous drill programs have been conducted over the years. Early campaigns utilised rotary, hammer, Reverse Evaluation and Caldwell bulk sample holes. Since the late 1970’s, RC has been the preferred method. In addition, a number of diamond drill holes were drilled in order to adjust density assumptions.
4.1 Data types
4.1.1 Drill hole database
The drill hole dataset for GEMCO has been collected during a series of drill campaigns over a number of years. These may be summarised as follows.
Drilling campaign Holes
1967 – 1970 drilling campaigns - R, CT, OH-Rotary holes R,CT,OH
1967 – 1976 RE Holes RE
1971 – 1976 drilling campaigns - OH – Hammer holes OH
1979 Caldwell holes drilling campaign CB
1979 and 1980 RC drilling RC4000 series
1984 RC drilling campaign RC5000 series
1985 RC drilling campaign RC5000 series
1986 RC drilling campaign RC5000 and RC 6000 series
1987 RC drilling campaign RC6000 series
1989 RC drilling campaign RC6000 series
1994 RC drilling campaign RC7000 series
1997 RC drilling campaign RC8000 series
2001 RC drilling campaign RC9000 series
2003 RC drilling campaign RC10000 series
2005 and 2006 RC drilling campaigns RC11000 and RC12000 series
2007 RC drilling campaign RC13000 series
2009 RC drilling campaign RC14000 series and RC15000 series
2010 RC drilling campaign RC16000 series (in progress)
Table 6 – Exploration history
Drill hole collar sites have been surveyed by the mine appointed surveyor. The drill sites are presented in the figure on the following page.
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Figure 5 – Drillhole locations
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4.1.2 2009 Drill Program
The main focus of the 2009 drill program was to update the model in areas planned to be mined in the next 5 years. The majority of drilling was carried out on a 60X60 m grid in order to bring these areas of the resource into the ‘Measured’ category. Drilling commenced in March 2009 and continued until the start of we wet season where it was ceased between December 2009 and March 2010. This report summarises drilling for the financial year (July 2009 to June 2010).
All drilling conducted this year was by Reverse Circulation method. A total of 1195 Reverse Circulation holes were drilled on the Mining Leases for a total of 33,203m. 9344 chip samples were collected for processing. A summary of the holes is listed below.
Lease Holes Metres #Samples
MLN1 0 0 0
MLN2 0 0 0
MLN951 81 2242 852
MLN952 184 4266 631
MLN953 192 5936 2500
MLN956 615 15638 4429
MLN957 7 325 136
MLN958 0 0 0
MLN959 59 2539 796
MLN960 0 0 0
MLN961 0 0 0
TOTAL 1138 30946 9344
Table 7 – FY10 Drill Program Summary
Of the 1139 holes drilled, 1051 contained manganese and 977 intersected manganese greater than 1m. 933 holes returned maximum downhole Manganese grades of greater than 40%.
Results are currently being validated. All 2009 drilling results will be included in the 2010 resource model update, while 2010 drilling results will be used in a later update after the conclusion of the 2010 drill season.
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Figure 6 – FY10 Drillhole locations
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4.1.3 Drill Hole Inclusion in Resource Model
GEMCO last produced a resource model in 2007. Recent drilling is currently being used to update this model with final validations now being performed. With respect to the 2007 model, the borehole database included 7690 drill holes used for the stratigraphic modeling databases and 7181 drill holes used for the sampling or assay database. The latter included 56,441 sample records. The included drill holes were almost entirely RC type holes.
As indicated above various campaigns of drilling have been conducted at Groote Eylandt, however there are significant differences in quality of the various drilling techniques and some samples are considered inappropriate for resource estimation.
All drill holes existing in GEMCO’s database have been assessed on individual merit to determine the validity of including all or part of their data. For example, early open precision drill holes and Caldwell bulk sampling drill holes with valid geological logging but containing samples with incompatible assaying techniques have been used to help control stratigraphic modeling and the estimation of yield and density, but have been excluded from the grade estimation. This approach is in line with recommendations contained in Dr John Cottle’s “Resource Estimation Models Review” of 1997.
All drill holes with valid geological logging were used to determine stratigraphic intervals and included: Caldwell bulk sampling; reverse evaluation (open percussion or rotary air blast RE, ST, WB); reverse circulation; and blast holes. Reverse circulation and some RE drilling are the only holes used for grade estimation. This data provides the most comprehensive coverage of the mining leases; were drilled for resource definition; and have compatible methods of assaying.
Section: 8450250mN (+/-10m)
Ore Horizon (400 – 800)
Stratigraphic Layer
Basement Contact
60m
3.5m
Section: 8450250mN (+/-10m)
Ore Horizon (400 – 800)
Stratigraphic Layer
Basement Contact
60m
3.5m
Figure 7 – Drill hole cross section
4.2 Sampling and analytical procedures
RC drill samples submitted for assaying have been split into various fractions as a means to replicate the recovered grade of manganese after scrubbing, screening and heavy media separation in the
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concentrator. Up to five sub-samples were prepared for each sample. The assay types are shown in
Table 6.
SAMPLE
Dry entire sample and jaw crush if required
Split - 25% D sample & 75% A sample
D sample A sampleHead sample Product (wet screen) sample
record weight
wet screen
record weight
dry +0.5mm fraction
record weight
riffle split to 200g riffle split to 200g
pulverise pulverise
XRF analysis XRF analysis
Figure 8 – Sample preparation flowsheet
Only the A and D assays have been used in this resource/reserve estimation. The D assay represents a true in-situ geological sample whilst the other splits more truly describe a metallurgical test to represent likely recovery from processing. Furthermore, it is assumed that the Type A assays give reasonable approximation of the final product, (some bias is recognised by the liberation of free silica during drilling). The MRT report discusses the apparent overestimation of SiO2 and underestimation of Mn being a consequence of the percussion drilling techniques breaking up material more than the concentrator does. However, the A assay has proven to be the most accurate emulation of the beneficiation plant. The laboratory uses internal and international standards. The latest drilling campaign included the use of field blank and duplicate samples as well.
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Assay Type Split Description
A assays Wash/Screen A split of the drill sample that is then wet screened at 0.5mm (early samples taken from 1979-1983 were based on +1mm screen)
B assays Gravity Sep The portion of the A Sample which has been further separated using bromoform (SG 2.89) heavy media liquid (the material removed is predominantly coarse quartz sand)
C assays Heavy Media The portion of the A Sample which has been further separated using tetra bromo-ethane TBE (SG 2.97) heavy media liquid (the material removed is predominantly coarse quartz sand)
D assays In-situ A split of the drill sample as received
E assays Met Test This preparation was only used for Caldwell bulk samples processed in the Metallurgical Test Plant.
Table 8 – Sample type
Drill hole samples were all assayed on site at the GEMCO laboratory using XRF (x-ray fluorescent spectrometer using borate beads) and AAS (atomic absorption spectrophotometer) techniques. The lab is audited under the NATA quality assurance system. Laboratory analysis standard operating procedures exist on site. The GEMCO Geological Drill Hole System (GGDS) contains assay values in percent for “A”, “B”, “C” and “D” type samples for Mn, Fe, SiO2, Al2O3, P, BaO, K2O, MgO, Na2O, CaO and SrO. The precision for Mn, Fe, SiO2, and Al2O3 constituents is 0.1%, for P it is 0.001% and 0.01% for the rest. It should be noted that only the mine laboratory has ever been used for analysis. On the few occasions off mine facilities were involved this was limited to sample preparation.
Field QA/QC controls consist essentially the placement of a blank or standard made up of local homogenised blast hole samples, at a rate of 1 blank per 60 samples. In addition a system of assaying field duplicates at a rate of 1 sample per 30 samples was done. Laboratory QA/QC controls includes regular standard calibrations and the consistent use of internal duplicates. Round Robin assaying has also been undertaken.
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Sample received at the laboratory
Sample registered in to CCLAS – Analysis by sample type
Analysis –XRF and balance moisture
Analysis – Mn by titration Analysis – XRF and oven moisture
ELEMENTS captured by CCLAS Flux weight Sample weight Hygroscopic moisture
ELEMENTS captured by CCLAS Sample weight
ELEMENTS captured by CCLAS Flux weight Sample weight Sample weight wet Sample weight dry
Sample fused into glass bead
Sample digested Sample diluted ELEMENTS – captured by CCLAS Gross diluted sample weight Aliquot weight
Sample fused into glass bead
Sample introduced into X-ray Sample titrated auto titrator
Sample introduced into X-ray
X-ray raw data captured by CCLAS Titrator raw data captured by
CCLAS
X-ray raw data captured by CCLAS
ELEMENTS and raw data converted to final data by CCLAS
Data reported to customer
Figure 9 – Assay flowsheet
4.3 Quality control and quality assurance results
QA/QC procedures followed during the recent drilling campaigns generated results as indicated in the following graphics; FIGURE 6 Drill “A” Sample duplicate results, FIGURE 7 Drill “D” Sample duplicate results, and FIGURE 8 Drill Field Blank sample results. The A and D sample duplicate results are indicated as are the blank sample results. The latter results (FIGURE 8) indicated that on 3 occasions assay results exceeded threshold boundaries and as a result investigations and corrective actions were undertaken timeously. The QA/QC system in place proved able to identify errors timeously and as a result confidence may be placed in the data set.
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FIGURE 6 Drill “A” Sample duplicate results
DE
SC
RIP
TIV
E S
TA
TIS
TIC
SO
rigin
alD
uplic
ate
Sam
ples
14
81
48
Min
imum
0.3
30
0.5
40
Max
imum
56.7
50
56.
810
Mea
n32
.02
53
1.41
3M
edia
n33
.41
53
2.08
0S
tan
dard
Dev
iatio
n12
.86
01
3.26
2V
aria
nce
56.7
50
56.
810
CoV
0.4
02
0.4
22
Cov
aria
nce
Pe
arso
n's
Co
eff
PR
SD
Per
cent
iles
101
4.51
51
2.2
4720
20.
654
20.
618
302
5.70
82
4.6
7140
30.
108
29.
318
503
3.41
53
2.0
8060
36.
114
35.
632
703
9.50
63
9.4
0980
44.
242
43.
510
904
8.29
64
7.9
0395
51.
184
51.
714
97.5
52.
009
52.
289
995
4.98
85
3.8
28
HA
RD
Pai
rsB
elow
B
in5
0-1
001
483
20-5
014
54
10-2
014
18
5-10
133
14>
51
191
19
16%
15
8.54
30
.930
QA
/QC
Gra
ph
s: R
AW
DU
P D
AT
A
X-Y
102030405060
10
203
040
5060
rig
inal
mn
_a (
%)
Duplicate mn_a (%)
O
Q-Q
102030405060
1020
30
405
060
Ori
gin
al
mn
_a (
%)
Duplicate mn_a (%)
HA
RD
51020501
00
0.00
1
0.010.11
10
100
101
00M
ean
of
Pai
rs (
mn
_a %
)
Half Absolute Relative Difference (mn_a %)
Rel
ativ
e P
reci
sio
n
0.1%
1.0%
10.
0%
100.
0%
110
100
Pai
r M
edia
n V
alu
e (7
pa
irs
mn
_a %
)
Relative Standard Deviation
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FIGURE 7 Drill “D” Sample duplicate results
DE
SC
RIP
TIV
E S
TA
TIS
TIC
SO
rigin
alD
uplic
ate
Sam
ples
148
148
Min
imu
m0
.500
0.7
00M
axim
um
54.
100
53.
700
Mea
n2
0.2
802
0.46
4M
edia
n1
8.5
001
8.35
0S
tand
ard
Dev
iatio
n1
1.7
891
1.82
1V
aria
nce
54.
100
53.
700
CoV
0.5
810.
578
Cov
aria
nce
Pea
rso
n's
Coe
ffP
RS
D
Per
cent
iles
106
.95
06.
900
209
.84
09.
800
3012
.41
01
2.8
0040
15.5
00
15.
540
5018
.50
01
8.3
5060
22.0
80
21.
640
7025
.55
02
5.9
1080
31.5
20
33.
060
9038
.03
03
7.6
8095
40.7
60
40.
995
97.5
44.2
85
42.
530
9947
.18
94
6.7
53
HA
RD
Pa
irsB
elow
B
in50
-10
014
80
20-5
014
81
10-2
014
713
5-10
134
18>
511
61
16
9%
135
.303
0.97
1
QA
/QC
Gra
ph
s: R
AW
DU
P D
AT
A
X-Y
0102030405060
010
2030
4050
60O
rig
inal
mn
_d (
%)
Duplicate mn_d (%)Q
-Q
0102030405060
010
2030
4050
60O
rig
inal
mn
_d (
%)
Duplicate mn_d (%)
HA
RD
5102050100
0.00
1
0.010.1110100
0.1
110
100
Mea
n o
f P
airs
(m
n_d
%)
Half Absolute Relative Difference (mn_d %)
Re
lati
ve P
rec
isio
n
0.1%
1.0%
10.0
%
100.
0%
110
100
Pai
r M
edia
n V
alu
e (7
pai
rs m
n_d
%)
Relative Standard Deviation
BHP Billiton Manganese CSG/GEMCO 2010 Group Technical Report
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FIGURE 8 Drill Field Blank sample results
Descriptive Statistics:All Data Cut Data
Count 116 113Min 22.54 43.20Max 48.37 48.37
Mean 45.423 45.754Std Dev 2.490 0.737
Var 6.1986 0.5425CoV 0.05 0.02p50 45.8000 45.8100p75 46.1800 46.2100p90 46.5250 46.5400p95 46.8225 46.8240
p97.5 47.1138 47.1160p99 47.1740 47.1752
GEMCO 2006 Blank_Mn_a (46.62%) Total Samples = 116 (98% Valid )
20.0
30.0
40.0
50.0
60.0
0 20 40 60 80 100
Time ->
As
say
Res
ult
(%
)
120
Blank_Mn_a ( (n=116) Upper Threshold (50.74%) Lower Threshold (42.5%)
4.4 Physical parameters
4.4.1 Density
Ian Lipton of Golder Associates was asked to review the densities to be used in the orebody model. To this end he undertook a thorough review of all the densities used over time in the various models. His findings are summarised as follows.
There are significant variations in dry bulk density across the deposits and between stratigraphic layers. These variations are primarily due to the naturally high geological variability of the ore
There was evidence that some of the data sets are biased. He concluded that the 1998 data and the 2002 recalibrated BPB data should not be used for resource estimation due to evidence of positive bias in both data sets
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The 2001 calibrated RC geophysical logging data is supported by physical measurements on core (AMDEL data) and appears to be generally reliable. He recommended that this data be used as the basis for resource estimation
Lipton recommended using a set of dry bulk density values based upon the 2001 RC data. These values should be applied to the resource model according to stratigraphic layer and domain codes in the model blocks. The schedule of densities used in the model as a result is provided as Table 11 in his report.
4.5 Aerial Survey
An annual aerial photograph was flown over the lease area in May 2010. The purpose of the flyover was to generate an annual aerial photo of the area as well as survey stockpiles in order to perform annual stockpile volume reconciliations.
Figure 10 – 2010 Aerial Photo
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5.0 Appendices
5.1 Appendix A: 2010 Aerial Photography Data
213752_Groote_TileGrid.dxf
orthoimage10_limits.dxf
pit_areas10.dxf
stockpile_areas10.dxf
Mosaics V2
JPEG2000 213752_groote_rgb.aux
213752_Groote_RGB.ers
213752_Groote_RGB.j2i
213752_Groote_RGB.jp2
213752_Groote_RGBI.ers
213752_Groote_RGBI.j2w
213752_Groote_RGBI.jp2
5.2 Appendix B: Drilling Data
GEMCO_2010_DrillData.xlsx
GEMCO_2010_DrillData_A_Assay.txt
GEMCO_2010_DrillData_Collar.txt
GEMCO_2010_DrillData_D_Assay.txt