Summary:
The Jimblebar mining operation is located 40 km east of Newman at the southern margin of the Pilbara Craton, which is comprised of large granitoid domes and batholiths separated by down-folded sequences of the Pilbara Supergroup sedimentary volcanic and intrusive rocks.
Bedded ore types classified as per host Archaean or Proterozoic banded iron formation, which are Brockman and Marra Mamba; also present is iron rich detrital material.
The Pilbara region comprises a portion of the ancient continental Western Shield that dominates the geology of WA. The Western Shield is comprised of pre-Cambrian, Proterozoic and Archaean rocks. The Pilbara Craton dates back to the Archaean and includes some of the oldest rocks in the world. It is overlain by Proterozoic rocks deposited in the Hamersley and Bangemall Basins. The Hamersley Basin which occupies most of the southern part of the Pilbara Craton can be divided into three stratigraphic groups; the Fortescue, Hamersley and Turee Creek Groups. Of the three groups, the Hamersley Group is the most relevant to the Jimblebar mine.
The Hamersley Group formed approximately 2,300 to 2,800 million years ago, is approximately 2.5 km thick, and conformably overlies the Fortescue Group. It consists of a sequence of Banded Iron Formation (BIF), dolomites, shales, and acid volcanics, and is intruded by dolerite sills and dykes. It contains both the Brockman Iron Formation and the Marra Mamba Iron Formation, which provide most of the iron ore deposits in the Pilbara.
The Jimblebar mine lies within the Ophthalmia Fold Belt and comprises a series of east-west trending folded and tilted formations:
- The Jeerinah Formation comprising interbedded shales, siltstone, chert and quartzite, and partly forming the footwall of the South Jimblebar mine pits.
- The Marra Mamba Iron Formation, which forms the rolling ridgeline south of the Copper Creek valley. It comprises BIF, shales and siltstone and significant haematite mineralisation forming the South Jimblebar orebody.
- The Wittenoom Formation, comprising shales, cherts and dolomite. This formation has been preferentially eroded forming a major paleo-valley in the Jimblebar region which has subsequently in-filled with Tertiary sediments. Weathering has resulted in karst-like development in the dolomites of the Paraburdoo Member. The West Angela Member, a shale unit, is situated between the Marra Mamba Iron Formation and the Paraburdoo dolomite Member.
- Mount McRae shale and Mount Sylvia Formation comprising shales, BIF and cherts.
- The Brockman Iron Formation comprising a sequence of interbedded BIF, shales, siltstones and cherts and significant haematite mineralisation in the Dales Gorge and Joffre Members, forming the Wheelarra and Hashimoto orebodies. The formation is resistant to weathering and forms the east-west trending Wheelarra Hill and Hashimoto ridgelines.
- The Tertiary valley fill sediments which overlie the Wittenoom Formation comprise semi-consolidated and cemented alluvium, colluvium, detritals and secondary calcrete.
Wheelarra Hill deposits
Wheelarra Hill is comprised of units from the Brockman Iron Formation which form a prominent strike ridge rising 200 m to 300 m above the surrounding countryside, notably at the northern boundary of M266SA. This Brockman Iron Formation is composed of chert, ferruginous chert and minor shale bands.
The Weeli Wolli Formation outcrops to the north of the Wheelarra Hill ridge. It consists of interbedded BIF, chert and shale. Closely associated with this formation are rocks of the Woongarra Volcanics, which consist of partially metamorphosed igneous rhyolite and rhyodacite as sills or flows.
In the valley to the immediate south of the Wheelarra Hill ridge, sedimentary deposits are found, taking the form of partly consolidated and cemented colluvium in Tertiary valley fill deposits. These deposits are derived from dissection of the Proterozoic rocks.
Quaternary deposits occur as scree slopes, in drainage channels and associated floodplains that lie at the base of the Wheelarra Hill ridge. A number of north-west trending faults (including the Wheelarra Hill Fault) occur across the Wheelarra Hill ridge.
Hashimoto deposits
The Hashimoto deposits are orebodies that are laterally continuous, extensive and also form prominent ridges (albeit somewhat lower than Wheelarra Hill) along the northern boundary of M266SA. Structurally, the deposits are dominated by folding in the east with diminishing deformation effect towards relatively flat lying strata in the west.
Iron mineralisation at the Hashimoto deposits is contained within the Dales Gorge Member and the Joffre Member of the Brockman Iron Formation. Tertiary-aged detrital and recent alluvium/colluvium deposits are prevalent on the northern and southern sides of the Hashimoto deposits, and in some cases obscure the orebody. Where drilling has occurred below the water table, ore has been intercepted at depths exceeding 120 m.
Small to medium scale thrust faulting has been mapped in the Hashimoto deposits, and is interpreted as being related to the hinges of small-scale folds. Immediately to the east of Hashimoto H1 deposit is Jimblebar Creek which acts as a natural truncation of the orebody and also contains large volumes of detrital material. This creek is considered likely to represent the surface expression of a geological structure (probable fault) running between the Hashimoto H1 deposit and the H2 deposit.
South Jimblebar deposits
Iron mineralisation at the South Jimblebar deposit is primarily hosted within the Mount Newman Member, but also occurs regularly within the MacLeod Member and the base of the West Angela Member of the Marra Mamba Iron Formation. High grade mineralisation is not wholly continuous across the entire orebody, being rather patchy in some places, particularly at the western end of the deposit. Low grade mineralisation can also vary greatly across sections of the deposit. The thickness of mineralisation varies greatly across strike from less than 10 m to over 200 m.
The South Jimblebar deposit varies from simple straight dipping units to intensely folded units, with some small areas of significant faulting. Folding varies from moderately to steeply dipping strata towards the north that typically does not alter greatly across strike and does not appear to directly control mineralisation.
The Marra-Mamba Iron Formation is characterised by the intermittent occurrence of fibrous material, which includes the family of mineral broadly called asbestos. Asbestos is the common term used to describe naturally occurring fibrous materials which occur in silicate minerals from the serpentine and amphibole groups. Crocidolite or blue asbestos is part of the amphibole group and has the potential to occur in the South Jimblebar Marra Mamba Iron Formation deposits. The Wheelarra Hill ridge that contains the Wheelarra Hill and Hashimoto deposits is part of the Brockman Iron Formation, which does not contain fibrous material.
Reserves at June 30, 2023
Mineral resource estimates cut-off criteria was based on deposit types identified in the joint venture. These are BKM and MM 54% Fe; CID 52% Fe and DID 58% Fe and less than 6% Al2O3.
Mineral Reserves estimates applied a cut-off criteria of 58% Fe.
| Category | Tonnage | Commodity | Grade |
|
Proven
|
871 Mt
|
Iron
|
61.6 %
|
|
Probable
|
341 Mt
|
Iron
|
59.1 %
|
|
Proven & Probable
|
1,212 Mt
|
Iron
|
60.9 %
|
|
Measured
|
164 Mt
|
Iron
|
57.9 %
|
|
Indicated
|
529 Mt
|
Iron
|
60.2 %
|
|
Measured & Indicated
|
694 Mt
|
Iron
|
59.7 %
|
|
Inferred
|
282 Mt
|
Iron
|
58.4 %
|
Summary:
Jimblebar is an open-cut mine.
Jimblebar Operations consisting of Bill’s Hill, Eastern Syncline and Mt Helen (jointly called Western Ridge deposits).
All mining areas within WAIO currently operate using conventional open-cut mining methods. Iron ore is a bulk commodity, and the orebodies are large and near surface, with a relatively thin overburden. The orebodies are generally shallow dipping, and most parts of the orebodies occur within depths of 200 to 300m from surface, thus leading to low strip ratios. These characteristics make the WAIO operations suitable for open-cut mining methods including drilling, blasting, loading and hauling.
WAIO open-cut mining uses face shovels, front-end loaders or backhoe excavators. The full bench is drilled and blasted for a 12 m height, sampled three times in 4 m increments and three 4 m flitches are then mined.
Drilling is separate for contour areas and production areas. Contour drilling is completed using smaller drills on contoured areas of the natural ground and production areas are relatively flat-lying large working areas drilled using larger production drills. Bulk explosive products, such as ammonium nitrate and fuel or emulsion, are mixed on the bench using Mobile Processing Units (MPUs) before being loaded into the drill holes.
Ore and Waste haulage is done with both manually operated and autonomous haul trucks. Waste is hauled directly to the adjacent waste storage areas either ex-pit (on surface) or inpit. Waste material is also utilised as fill material for development works and rehabilitating the completed waste dumps.
Ore is hauled to the Run-of-Mine (ROM) pad where it is stockpiled and blended for ore quality before feeding to the crushers using loaders. Some of the ore suitable for blending is also hauled directly to the crushers.
Summary:
WAIO’s run-of-mine (ROM) ore is hematite type direct shipping ore (DSO) with average iron content not less than 60% for Brockman (BKM) and Marra Mamba (MM) ore types and not less than 56.5% for Channel Iron Deposit (CID) ore type. The ore is also higher-quality with deleterious contents within acceptable limits and is capable of being fed to the blast furnace for iron and steel making, without the need of any concentration or beneficiation. Therefore, the processing involved is simple crushing and screening of the ROM to produce the two industry-standard DSO marketable ore types, namely lump (with nominal particle size >6.3mm) and fines (with size <6.3mm).
A dry processing method is used for crushing and screening. This method is simple and well understood and widely used by most DSO producers in the Pilbara. The ROM ore is first crushed in a primary crusher set up near the mine. The crushed ore is then transported via an overland conveyor to an Ore Handling Plant (OHP), housing secondary and/or tertiary crushers and screens, for further crushing and screening. The OHPs are located close to a train load-out (TLO) station. For larger mines, two or more OHP’s are centrally located around the TLO station(s) and form a processing hub. Currently there are four processing hubs in WAIO, namely, Newman Operations, Jimblebar, Mining Area C - South Flank and Yandi.
All dry OHP’s typically recover 100% mass of the ROM feed in the form of either lump or fines.
Jimblebar Processing Hub
Jimblebar processing hub started production in 2013 and currently has three primary crushers closer to mining sites and one central OHP with a nominal capacity of 71 Mtpa. In addition to the OHP, this processing hub has a stockyard blending facility and a train load out. This hub processes ROM ore sourced from both Brockman (BKM) and Marra Mamba (MM) deposits at proportions determined by the mine schedule.
The OHP recovers 100% mass of plant feed and produce both lump and fines ore types with a nominal split to lump stream of 30-40%.
Summary:
Water and Pipelines – groundwater is the primary freshwater source for WAIO and is extracted from production and dewatering bores with abstraction volumes as per licence requirements for use in all mining and processing operations. The water is supplied to various sites through a network of over and underground water pipelines along with associated tanks and control infrastructure. Water consumption is linked to mining rates, and water supply and infrastructure capacity is included in development plans accordingly.
Water use is primarily for dust suppression during mining and processing and shows seasonal variation, consumption increasing in the hotter weather.
Once operational demand has been met, surplus water may remain that needs to be disposed of in line with environmental approvals and licenses. WAIO has an ongoing program to return water to ground via injection bores and infiltration structures. This program aims to treat water resources in the Pilbara region in a responsible way and, where practicable, maintain water levels in local aquifers to mitigate impacts and preserve water for future use.