Overview
Stage | Preliminary Economic Assessment |
Mine Type | Open Pit |
Commodities |
- Iron (hematite)
- Iron (magnetite)
|
Mining Method |
|
Processing |
|
Mine Life | 31 years (as of Jan 1, 2019) |
Latest News | Macarthur Minerals Closes Private Placement October 22, 2020 |
Source:
p. 15
The Lake Giles Project area comprises 15 Mining Leases which are all held by Macarthur Iron Ore Pty Ltd (MIO), a 100% owned subsidiary of Macarthur Minerals Limited (MMS).
Summary:
Regional Geology
The tenements held by MMS are known to be prospective for nickel and gold as well as iron ore. The iron mineralisation is related to the extensive Banded Iron Formation (BIF) that occurs throughout the tenements. Aerial magnetic data shows that BIF units totalling at least 73 km of strike occur within the tenements, mostly under shallow cover. Iron mineralisation currently being explored comes in two forms:
- Magnetite – present in the fresh BIFs along with high quantities of silica. This is the primary unaltered form of BIFs at site and in general has not been subject to any significant later iron enrichment.
- Hematite/Goethite– present in the weathered BIFs with lower quantities of silica. It is the product of supergene enrichment of the BIFs, which results in the leaching of the silica from the primary fresh BIFs and in some cases addition of iron from mineralising solutions. This results in elevated iron content in comparison with the fresh BIF.
MMS’s tenements cover a portion of the Yerilgee Greenstone Belt which is over 80 kilometres in length and up to 10 kilometres wide, and lies within the Southern Cross Province of the Yilgarn Craton. The Yilgarn Craton consists of multiple lenticular greenstone belts surrounded by variably foliated gneissic granitoids.
The greenstone belts consist of metamorphosed ultramafic, mafic and sediments, including banded iron formation (BIF) which are Archaean in age and are commonly intruded by mafic, intermediate and granitic rocks.
The greenstone belts are generally metamorphosed to mid greenschist facies towards the central parts of the belt and lower amphibolite facies on the edges of the belt where they are in contact with the granitoids.
Local Geology
The parts of the north-northwest trending Yerilgee greenstone belt covered by the project tenements are underlain by a layered succession of Archaean rocks. At the interpreted base of the succession is a sequence of high-magnesium basalt flows more than one kilometre thick overlain by komatiitic ultramafic volcanic rocks with narrow interflow BIFs and in some cases other sedimentary rocks. Further high-magnesium basalt lavas with occasional interflow BIFs overlain, possibly unconformably by sedimentary rocks (cherty, silicified, pyritic and graphitic) are thought to form the top of this sequence. In places gabbroic sills have been intruded into the lower mafic and ultramafic lavas. These are believed to be co-magmatic with the upper high-magnesium basalts. The elongated lens shaped Yerilgee belt is bounded by major north-northwest trending fault/shear zones.
Property Geology and Mineralisation
The iron ore mineralisation consists of secondary pisolite mineralization, primary magnetite mineralization associated with un-oxidized banded iron formation (BIF) and ultramafic rocks, and goethite-hematite mineralization associated with oxidized BIF.
The hematite/goethite units are the source of MMS’s hematite Mineral Resources to date and exist largely as a supergene product. Weathering has resulted in the leaching of the majority of the silica from the BIFs, thus producing a rock rich in iron and low in silica. These enriched bands vary from 1 to 30 metres in true thickness and are largely steeply dipping by 70o to 90o.
The mineralisation at the Moonshine and Moonshine North magnetite deposits is associated with primary magnetite mineralization hosted by banded iron formation (BIF). The multiple BIF units steeply dip 75° to 85° to the west and strikes approximately 320° and 335° respectively with outcrops (and the units have an average thickness of 15 m, over a strike length of 17 km.
The project area is comprised of multiple parallel bands of BIF, many of which are enriched, with varying (1 to 30 metres) thicknesses. The strike of these bands is largely NW-SE. A number of folds with a NW plunge have been identified with further work into the structure of the deposit on-going. The strike extent of the main ridge line at Snark is 5.9 km and the package consisting of the multiple BIF bands along with the inter-bedded ultramafics has a thickness of approximately 500 m.
Summary:
At this level of the study, the general options considered to mine the ore body are:
- Mining shall be conducted by conventional drill, blast, load and haul mining methods
- Ore shall be hauled to the Run of Mine (“ROM”) pad for crushing and then ore product conveyed to a concentrate plant. Concentrate product shall then be road hauled to a rail loadout and then by rail to the Port of Esperance for export sale.
A mining fleet comprising 2 x 110 tonne-class excavators (Hitachi EX1200 or equivalent) loading 90 tonne haul trucks (Cat777 or equivalent) would capable of achieving the annual ex-pit ore and waste movement. It is expected that the excavators would move between ore and waste areas, and between individual pits in order to maintain continuity of ore supply. It is expected that waste rock would be hauled to either ex-pit waste dumps or mined-out pits (where possible).
For the purpose of this Study, the mining at Lake Giles would be by open pit and based on conceptual resource size and production rates of 3 Mtpa concentrate. A contractor would be engaged to undertake drill and blast, load and haul to the primary crusher and waste/low grade stockpile. Further “sterilisation” drilling would be required before waste dump and crusher locations can be established.
For the drilling and blasting, bench heights would be optimised to suit the drill rig and single pass drilling. Drilling and blasting, bench heights would be undertaken on 5 m benches. The ore and waste would be mined on 5 m benches, or 2.5 m flitches, depending on the selectivity required. ANFO would be used in the top benches above the natural water table.
Explosives would be delivered on a "down the hole" basis and only initiating materials would require storage in on-site magazines.
Crusher / Mill Type | Model | Size | Power | Quantity |
Jaw crusher
|
|
|
|
2
|
Cone crusher
|
|
|
|
2
|
SAG mill
|
|
|
|
1
|
Ball mill
|
|
|
|
2
|
Tower / Vertical mill
|
|
|
|
2
|
Summary:
The development of the concentration process for the Project would be influenced by several key elements. These include conservation of water, minimum power consumption, the competent and abrasive nature of the ore, and the presence or otherwise of asbestiform minerals within sections of the mineralisation. (Though the probability of the presence of asbestiform minerals is low, mineralogical test work should be carried out at an early stage to resolve the question). Whilst addressing all of these issues the processing plant must also achieve efficient and economic recovery of the contained magnetite.
The Hematite resource is distinct from the magnetite zones and only requires appropriate selection of high grade ore to obtain the required grade. This material would be subjected to conventional 3 stage crushing and milling to allow mixing with the magnetite product.
Magnetite Processing
In order to produce 2.5 Mtpa concentrate, assuming a weight recovery of 38%, an estimated 6.6 Mtpa of feed to the process plant would be required. The first stage is primary crushing to a size suitable for feed to a Semi Autogenous Mill.
It is likely that the primary crusher(s) would be located close to the plant operation. The coarse ore would be stored in a stockpile to supply surge capacity between the mine and the plant.
Primary milling would be by Semi-Autogenous grinding in closed circuit with screening to produce an appropriate size to feed the first stage of wet low intensity magnetic separators (LIMS), known as cobbers. The cobbing stage should reject the initial tailings while maintaining a high level of magnetite recovery. A coarse tails is produced at this stage and, as water is often of major consideration in tailings treatment, a water recovery system should be included.
Cobber concentrate would need to be reduced again in size. A ball mill would be used in closed circuit with cyclones for this purpose. The cyclone overflow would be the feed stream for the rougher LIMS stage.
Assuming the Lake Giles ore has similar characteristics to other Australian magnetite ore bodies, it is likely that a third stage of grinding to 80% passing 30 to 45 micron would be required. This duty is best suited to a pair of fine grinding mills such as the Vertimill. The product from these mills would feed the finishing stage of magnetic separation. This is a three stage drum which gives a progressively cleaner product grade and helps to eliminate any contamination due to entrapment.
Hematite Processing
The hematite material would be mined from the deposits at a grade that allows blending with the magnetite to make a saleable product.
The ROM material would be fed to a Grizzly feeder to allow fine material to bypass the Jaw Crusher. After this initial size reduction the material would be screened by double decked screens. These would remove the product material and divide the coarse material into secondary and tertiary crusher feed. These two streams would be crushed in cone crushers and then mixed with the Screen Feed material.
This material would be transported to a milling circuit to grind the mill to a size suitable for mixing with the Magnetite concentrate.
Flow Sheet:
Summary:
The development of the concentration process for the Lake Giles Project would be influenced by several key elements. These include conservation of water, minimum power consumption, the competent and abrasive nature of the ore, and the presence or otherwise of asbestiform minerals within sections of the mineralisation. The concentration process may include:
- primary crushing
- secondary/tertiary crushing (if required)
- primary milling by Semi-Autogenous Grinding
- first stage of wet low intensity magnetic separators (LIMS)
- secondary milling by ball mill
- second stage, double drum wet LIMS
- tertiary milling by Vertimills
- finishing stage of magnetic separation by triple drum wet LIMS
- Dewatering of the various final streams.
Recoveries & Grades:
Commodity | Parameter | Avg. LOM |
Iron (hematite)
|
Head Grade, %
| 56 |
Iron (magnetite)
|
Head Grade, %
| 30 |
Iron (magnetite)
|
Concentrate Grade, %
| ......  |
Iron (magnetite)
|
Recovery Rate, %
| ......  |
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Reserves at June 13, 2019:
The resource is quoted from blocks above 40Fe % cut-off grade, except Moonshine where resource is quoted from blocks above 50 Fe %.
Category | Tonnage | Commodity | Grade |
Indicated
|
54,460,000 t
|
Iron (hematite)
|
47.2 %
|
Inferred
|
25,990,000 t
|
Iron (hematite)
|
45.4 %
|
Mine Management:
Job Title | Name | Profile | Ref. Date |
.......................
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Dec 14, 2020
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Corporate Filings & Presentations:
Document | Year |
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2020
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2020
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2019
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- Subscription is required.
News:
News | Date |
Macarthur Minerals Closes Private Placement
|
October 22, 2020
|
Macarthur Minerals Balance Sheet Materially Strengthened by Financing Package
|
October 13, 2020
|
Macarthur Minerals Ltd.: Technical Report for Lake Giles Magnetite Mineral Resource
|
October 1, 2020
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Macarthur Minerals Ltd.: Moonshine Magnetite Resource Upgrade
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August 11, 2020
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Assays completed for infill drilling of the Lake Giles Iron Project
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May 5, 2020
|
Macarthur Minerals: Major intersections of magnetite mineralisation confirmed at Lake Giles Iron Project
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January 16, 2020
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Macarthur Minerals Secures Access to Land for Infrastructure at Its Lake Giles Iron Project in Western Australia
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December 23, 2019
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Macarthur Minerals Intersects High Grade Magnetite at Its Lake Giles Iron Project in Western Australia
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December 10, 2019
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Macarthur Minerals Seeks TSX-V Approval to Close Financing on the Lake Giles Iron Ore Project
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July 5, 2019
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Macarthur Files Technical Report for Lake Giles Iron Ore Project
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June 17, 2019
|
Macarthur Minerals Provides Update on Private Placement
|
May 31, 2019
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Macarthur Minerals Announces Glencore Participation in Financing
|
May 16, 2019
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Macarthur Minerals Provides Update on Private Placement
|
April 24, 2019
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Macarthur Minerals Limited: Drilling Contractor Appointed to Commence Drilling at the Moonshine Magnetite Project at Lake Giles
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April 18, 2019
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Macarthur Minerals Signs 10 Year Iron Ore Off-Take Agreement for the Lake Giles Iron Project in Australia With Glencore International A.G.
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March 21, 2019
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Macarthur Minerals Announces US$6 Million Financing to Complete Moonshine Magnetite and Ularring Hematite Iron Ore Bankable Feasibility Study
|
March 19, 2019
|
Aerial view:
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