2010 Annual Group Technical Report MLN 2 - MLN 3 GEMCO MLN ...€¦ · Groote Eylandt Mining...

BHP Billiton Group Level Document – Internal Use Only This document may contain proprietary and/or confidential information. This document is a controlled document. The controlled copy is

maintained electronically by the Company Secretariat. Any printed copy of this document is an uncontrolled copy.

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.

Version: 1.0 Annual Group Technical Report Page 2 of 29 15 September 2010

This document may contain proprietary and/or confidential information. This document is a controlled document. The controlled copy is maintained electronically by the Company Secretariat. Any printed copy of this document is an uncontrolled copy.


Version: 1.0 BHP Billiton Group Level Document Page 3 of 29 15 September 2009


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




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.




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


Version: 1.0 BHP Billiton Group Level Document Page 6 of 29

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

15 September 2009 This document may contain proprietary and/or confidential information. This document is a controlled document. The controlled copy is





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







2004 (Snowdens / Golders) GEMCO Model 153.35 Mt


2005 estimation (2004 Model) 173.3 Mt *

2006 estimation (2004 Model) 169.4Mt

2007 estimation (2007 model) 169.6Mt



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.




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.



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 2 1.38 Power line lease 29/9/1989*

MLN 3 1.65 Bridge lease 24/7/1985*

Table 2 – Tenement list






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




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




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.



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)





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






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.




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




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


1986 RC drilling campaign RC5000 and RC 6000 series







2005 and 2006 RC drilling campaigns RC11000 and RC12000 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.



Figure 5 – Drillhole locations






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.



Figure 6 – FY10 Drillhole locations





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





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.






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.



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.






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




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



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





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






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

Date post:	24-Aug-2020
Category:	Documents
Upload:	others
View:	3 times
Download:	0 times

2010 Annual Group Technical Report MLN 2 - MLN 3 GEMCO MLN ...€¦ · Groote Eylandt Mining...

Documents