ASX-listed explorer, Impact Minerals looks to be on the money with its first reconnaissance drill program at its Rockwell prospect encountering widespread occurrences of copper-nickel-PGE anomalies over about 1.5 kilometres. The drilling included an RC hole the Perth-based company described as a breakthrough hole that intersected elevated copper over a 25m-wide sulphide zone.
The Rockwell prospect forms part of the Little Broken Hill Gabbro intrusions area at Impact’s Broken Hill project in NSW where it recently drilled 28 aircore and RC holes for an aggregate 2,412m, with results received for about half of them so far and the balance pending.
The company says drill and portable or hand-held X-ray fluorescence, or “XRF” gun-generated assays indicate copper-nickel mineralisation appears to increase in thickness and grade from north to south into a priority target area interpreted to contain potential “feeder zones” to the main Little Broken Hill Gabbro. Grade and thickness also seem to be increasing with depth, Impact says.
Feeder zones are fault-controlled conduits through which hot magma migrates into a larger intrusion from depth and where nickel-copper sulphide deposits are commonly found.
The mineralisation occurs mostly in an ultramafic unit at the base of the Little Broken Hill Gabbro intrusion and, according to the company, points to the highly prospective nature of the entire 6km-long intrusion for magmatic nickel-copper-PGE sulphide deposits as suggested by its previous work in the area.
To the south at Rockwell, several faults cut through the intrusion and Impact considers these priority targets for follow-up drilling.
Significant intercepts from the scout drilling at Rockwell to date include 6m going 0.72 grams per tonne 3PGE and 760 ppm copper from surface including 1m at 1.2 g/t 3PGE and 0.2 per cent copper from 4m, 7m at 0.2 g/t 3PGE and 0.2 per cent copper from surface, and 3m at 0.26 g/t 3PGE and 0.15 per cent copper from 23m.
Impact pointed out intersections have yet to be received for a handful of holes that contain thick zones of 1-5 per cent disseminated copper sulphides.
The Little Broken Hill Gabbro, which sits about 25km south of Broken Hill, is the largest of a suite of mafic to ultramafic intrusions that occur in a 40km-long belt from Little Broken Hill in the south-west to Impact’s Red Hill, Darling Creek, Platinum Springs and Moorkai areas in the north-east.
The company has built a large library of new data from the significant drill programs it has undertaken at the Broken Hill project, with assay results still outstanding from the Little Broken Hill Gabbro, Platinum Springs, Red Hill and Dora East prospects.
It says a detailed interpretation of all of the data is called for in order to prioritise areas for follow-up drilling. Impact intends resuming drilling at Broken Hill as soon as practicable in the March quarter next year.
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By Matt Birney
