A diamond drillhole described by Western Mines Group as something of a “wildcat” at its Mulga Tank project in Western Australia has helped expand evidence of significant massive nickel sulphide formation processes out to about 4.5km
The company says results from the hole (known as MTD027) opens up the complex’s eastern margin as an exploration target for massive nickel sulphides and shows the deposit extends to much greater depth than the western side. It says it has significantly expanded its understanding of its ultramafic-hosted, nickel-bearing sulphide system in its flagship Mulga Tank ultramafic complex.
The hole is the sixth in the company’s phase two program. It was drilled to 1662m downhole and was designed to test a coincident gravity and magnetic high, a minor moving loop electromagnetic survey (MLEM) anomaly and the presence of nickel sulphide mineralisation far out on the eastern side of the complex, in an area that has had no previous drilling.
Management says the hole successfully intersected more than 1500m of variably serpentinised and talc-carbonate-altered high magnesium meso-adcumulate dunite ultramafic rocks beneath 84m of sand cover, running from 84m to 1630.9m. It then encountered a basalt and silicified shale footwall to 1662.3m, with more than 950m of cumulative disseminated nickel sulphide mineralisation and many remobilised sulphide veinlets.
“MTD027 was something of a ‘wildcat’ hole out on the eastern margin, in an undrilled area of the Mulga Tank Complex. Very encouragingly nickel sulphide mineralisation was seen down the length of the hole. Given the visual observations we were committed to intersecting the basal contact in this area, and the hole went deeper than expected, ending up being the deepest drilled to date. The footprint of the sulphide mineral system has now been demonstrated across the entire ~4.5km wide body of the Complex from hole MTD022 in the west to this hole MTD027 in the east. The results of the drilling continue to refine our model of the Mulga Tank Ultramafic Complex.“ Western Mines Group managing director Caedmon Marriott
The phase two program includes two deep holes that have already been drilled with the aid of the company’s $220,000 Exploration Incentive Scheme (EIS) funding from the State Government. The second EIS drillhole was completed recently to a depth of 1548.3m – the deepest hole ever drilled at the Mulga Tank project.
Overall, Western Mines says its wildcat hole showed several similarities to the two EIS deep holes, with the textures of the host dunite possibly indicating a slightly higher position in the intrusive system. Similar intersections of disseminated sulphides to the EIS holes were observed, in addition to frequent examples of remobilised massive sulphide veinlets logged down the hole.
Mulga Tank is a major ultramafic complex in the underexplored Minigwal greenstone belt in Western Australia’s Eastern Goldfields, where historical and company exploration results and visual observations offer significant evidence for an extensive working nickel sulphide mineral system – believed to be highly prospective for nickel-copper-platinum group elements (PGE) mineralisation.
The company’s initial geological model of the Mulga Tank ultramafic complex defined the main body as being a large lopolith, a saucer-shaped intrusion or sub-volcanic sill of largely dunite ultramafic rocks similar to the geological formations of the renowned Perseverance and Mt Keith ultramafic nickeliferous complexes. But Mulga Tank is thought to be less deformed and oriented in a nearly horizontal position.
As the eastern margin of the complex has not been previously drilled, it was expected from the company’s initial “saucer” model that the latest hole would intersect the footwall of the intrusion at a depth of between 750m and 800m, but it eventually intersected it at 1630.9m. Western Mines now believes one of its previous drillholes had ended in the dolerite sill and that the eastern margin of the “saucer” is more steeply-dipping than the western margin and extends to greater depth.
Accordingly, the company’s model appears to be more of a moderately deformed wedge shape, with a thin western edge tapering to thin outcrop, and a thick eastern edge.
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