The Alvey prospect is located in the East Deering Hills, within the north-western part of the Musgrave Ranges region of South Australia. The prospect lies on the eastern boundary of a reserved small exploration licence area previously held by the...
The Alvey prospect is located in the East Deering Hills, within the north-western part of the Musgrave Ranges region of South Australia. The prospect lies on the eastern boundary of a reserved small exploration licence area previously held by the Minister for Mines. The now surrounding, recently granted EL 3942 (for which Mithril Resources can earn up to 80% equity from Barrick Gold's 100% wholly owned subsidiary, Delta Gold NL) lies entirely within the Anagu Pitjantjatjara Aboriginal Lands, approximately 125 km to the south-west of Uluru. Both the prospect and EL 3942 covers portions of the Giles Complex, an east-west trending belt of mafic and ultramafic intrusive rocks more than 300 km long which have intruded highly metamorphosed units of the Musgrave Province basement. At the Alvey prospect, historical geological mapping by Rio Tinto identified a 15-25 m wide zone of PGE mineralisation grading up to 15 m @ 0.72 g/t Pt+Pd at surface, over a 500 m strike length that remains open in all directions within these Giles Complex rocks. Three RC percussion holes drilled by Rio Tinto confirmed that this horizon continues at depth. Application was made by Mithril Resources during 2007 for PACE Round 5 subsidy funding to assist it to drill diamond holes targeting a possible eastern extension of this mineralised horizon beneath thin sand cover, to try to determine whether it persists over a 1.2 km strike length. It was anticipated that the new drilling would provide key information about controls on any higher grade mineralisation and an indication of the economics of this system, both of which will be useful for targeting and assessing other PGE prospects within the Musgrave Province in South Australia. It was planned that the drillholes would target the mineralised melagabbro - gabbro-norite contact within EL 3942, approximately 800 m east-northeast of Rio Tinto's drillhole RC00AL001. To assist in accurately targeting this contact, Mithril Resources conducted 5 detailed ground magnetic traverses with 100 m line spacing and 10 m station intervals, and completed a RAB-aircore drilling traverse, to more accurately locate the mineralised contact. For the subject PACE project, two adjacent diamond holes totalling 789 m were drilled, 200 m apart towards the same azimuth (358 degrees magnetic and dipping at -60 degrees). Each was rotary mud drilled from the surface to about 13 m depth, and then diamond cored HQ until hard rock was encountered at about 30 m depth, whereupon the core bit gauge was switched to NQ and coring was continued at this size until hole TD. Core recovery was 100% throughout. Both drillholes encountered similar mafic and ultramafic rocks, principally cumulus hypersthene gabbros and norites separated by coarse grained pyroxenites. These had been intruded by magnetite-bearing quartz-poor dolerites that often display chilled margins. Sulphide mineralisation is rare, very fine grained and pyrite-dominated. Drill core sample analytical results showed the following PGE anomalism: MAD1 14.4 m @ 0.465 ppm Pt+Pd over the depth interval 273.0-287.4 m, including 6 m @ 0.812 ppm Pt+Pd from 277-283 m; MAD2 2.8 m @ 0.451 ppm Pt+Pd over the depth interval 358.0-360.8 m, and 17.1 m @ 0.494 ppm Pt +Pd over the depth interval 382.0-399.1 m, the latter including 8 m @ 0.771 ppm Pt+Pd from 386-394 m. Anomalies in other elements were absent: the maximum sulphur assay was 0.26% S. Analysis of the heavier element distribution, Cr, Fe, Mn, Ni and V, suggested that the Giles Complex in this area is not overturned. In conclusion, Mithril Resources reports that the PACE drilling has successfully traced the PGE mineralisation from Mount Alvey 1100 m east along the 'magmatic strike' of the Giles Complex. It also indicated that there is more than one Pt+Pd mineralised horizon, and the company believes that any one of these horizons has the potential to host a significant PGE deposit. Analytical results from the drilling also indicate that defined gabbroic/ultramafic 'units' (or layers) are in fact differentiated. The degree of differentiation of individual units suggests that the more primitive or basal portion of the magmatic pile is the northern contact. This northern contact therefore should be the focus of search for magmatic Ni/Cu/PGE sulphides. Further exploration should address the easterly extension to these PGE mineralised horizons to try to locate higher grades or thickening of the PGE horizon, and also concentrate on the interpreted northern basal contact with the Birksgate Group gneisses, looking for magmatic Ni-Cu-PGE sulphide mineralisation.
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