Magnetite Mines (ASX:MGT) reports it has completed the mineral resource estimate (MRE) for the Muster Dam Iron Ore Project in South Australia.
The company, which exhibited at the International Mining and Resources Conference (IMARC) in Sydney last week, says the MRE has increased from 4.19 billion tonnes to 5.74Bt (combined inferred and indicated resources) with 1.55Bt tonnes at 1.52% mass recovery completed to JORC 2012 code and guidelines at the inferred classification.
Magnetite reports the Muster Dam prospect represents an exploration and development opportunity for the company, and is hosted in the same geological unit as the Braemar Iron Formation, and the project has a number of ‘synergies’ with the Magnetite’s flagship Razorback Iron Ore Project, located around 110km to the south west of Muster Dam.
The new MRE applies to the Muster Dam prospect within the EL6746 tenement only, and outside of the deposit, Magnetite says ‘prospectivity’ has been demonstrated at the Peaked Hill, Duffields and Surrender Dam prospects from previous exploration drilling and geophysical surveys.
These prospects remain a priority as the company seeks to expand its portfolio of iron prospects
These prospects remain a priority as the company seeks to expand its portfolio of iron prospects, and it also intends to continue to prioritise the development of the Razorback Iron Ore Project while evaluating the Muster Dam prospect, which has the ‘potential’ to offer a logical and natural expansion pathway beyond the development of Razorback.
Magnetite also reports the Muster Dam inferred resource estimate adds tonnage to the company’s global MRE for iron mineralisation, and at 5.74 billion tonnes, the company holds the ‘largest’ mineral resource in the Braemar Iron Formation.
The company says a program of reverse circulation (RC) and diamond drilling was undertaken at Muster Dam in 2011 drilled to a depth of 300m, and this was considered ‘sufficient’ to define an JORC-compliant inferred resource estimate.
A total of 53 RC and 8 diamond drillholes were drilling during this campaign totalling 13,912m of RC and 2,500m of diamond core, and an initial RC program of 36 holes for 10,800m provided insufficient overlap of geology on some sections and required infill drilling, resulting in a further 12 RC holes for 2,279m being drilled.
Magnetite also notes 6 diamond core holes totalling 1,800m were drilled to confirm structural and lithological properties of the Muster Dam deposit with 2 diamond core holes twinned alongside 2 RC holes to confirm the RC DTR results were representative of the magnetite iron deposit.
Detailed downhole and wireline density and magnetic susceptibility data used in conjunction with DTR results and lithological logs has allowed the correlation of individual lithological units between sections at Muster Dam, and this consistent correlation of lithological units between sections has also permitted a preliminary lithostratighraphy to be determined by the company.
Magnetite found the thickness of individual lithostratighraphy units to vary between sections, which is interpreted to be due to slight facies change along strike or drillholes drifting off section shifting the relative position of the point that defines a stratigraphic boundary between drillholes.
For the purpose of constraining the current resource model, Magnetite reports logged lithologies were used to generate diamictite and siltstone and sandstone wireframe solids using the implicit Geological Modelling functions provided in Micromine 2022.5 software.
The company adds density data was available from downhole geophysical surveys at 10cm intervals and physical measurements on diamond drill core samples, with the latter being carried out by the previous owner of the tenement in 2011 and also more recently as a validation check by Magnetite in October this year.
All drilling samples from the 2011 resource drilling program were sent to ALS Laboratory Services for Davis Tube Recovery (DTR) and XRF analysis which produced 2 magnetite concentrate samples from the DTR sample subject to Fusion XRF.
The Muster Dam Iron Ore Project is located in the North East pastoral district of South Australia around 90km southwest of Broken Hill, and located within tenement EL6746 includes the iron prospects known as Muster Dam, Surrender Dam, Duffields and Peaked Hill.
Muster Dam lies within sedimentary lithologies of the Adelaide Geosyncline, a linear north-south to northeast trending tectonic rift basin comprising sediments deposited during the late Proterozoic and early Cambrian eras, and magnetite mineralisation within the project is hosted in Neoproterozoic glaciogenic meta-sediment of the Braemar Iron Formation stratigraphically equivalent to the Razorback Iron Ore Project deposits.
Magnetite says the rocks exposed at Muster Dam contain diamictitic siltstones, quartz sandstones, calcareous siltstones, dolomite and magnetic ironstone units of the Braemar Ironstone Facies, and the ironstones are an example of glaciomarine Raptian-Sturtian sedimentary iron-formation type which has been a world-wide occurrence in the Neoproterozoic.
In aeromagnetic surveys, the company reports the project comprises a series of airborne magnetic features that occur as a set of large, curvilinear, high-amplitude anomalies interpreted to be regional scale folding of the magnetite rich Braemar Ironstone.
The company also states the mineral composition and mineralisation style is consistent with other regional Braemar Formation magnetite mineralisation, and QEMSCAN and Petrology by Pontifex and Associates describe the host rock iron mineralisation as discrete crystals of magnetite and hematite within a silicious matrix.
All individual crystals of magnetite and hematite (iron oxides) are also free of inclusions, either of one within the other or of gangue, and the company expects the bonding of iron oxides with the major host rock gangue mineral of biotite to be ‘relatively weak’, given the different hardness and morphologies of these 2 adjacent minerals and the lack of intricate inter-growths.
Magnetite notes this ‘weak’ bonding is demonstrated in other Braemar Formation deposits as having ‘low’ work index or ‘low’ specific energy requirements during blasting, crushing and grinding relative to traditional iron ore deposits hosted in banded iron formations (BIF).
Magnetite Mines is an ASX-listed iron ore company focused on the development of magnetite iron ore resources in the Braemar iron region of South Australia.
Its assets include the Razorback Iron Ore Project and the Muster Dam Iron Ore Project.
Images: Magnetite Mines Ltd
