Lodestar's exploration strategy at the Penfold project has focussed on the search for high value massive sulphide nickel mineralisation, utilising moving loop electromagnetic (EM) surveys to define conductors associated with the ultramafic sequences. Area selection for the EM surveys was based on historical information, a review of the gold exploration database and correlation of ultramafic sequences with known nickel sulphide mineralisation. Three areas, having a combined strike length of 19 kilometres or approximately 40% of the ultramafic interpreted stratigraphy, have been tested by EM surveys.
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| Moving loop EM surveys completed by Lodestar (aeromagnetics TMI analytic signal image, MGA94 Zone 51) |
Lodestar's exploration has concentrated on evaluating the three areas covered by the EM surveys
- Abattoir prospect, identified by Placer drilling in 1971, was a priority target for drill testing. Four RC holes were drilled into the eastern contact over a 50m strike of the ultramafic sequence to test the reported mineralisation, with a best intersection of 6m at 0.46% Ni and up to 0.1% Cu and 3m at 0.49% Ni (maximum 0.54% Ni) and up to 0.22% Cu. A single vertical diamond drill hole also targeted the eastern contact and intersected the contact in the precollar. The contact zone reported 10m at 0.47% Ni and up to 0.11% Cu (maximum 0.59% Ni). Subsequent analysis of geochemical data suggests that the eastern contact is the hangingwall contact of the ultramafic sequence. Further exploration of the western footwall zone is indicated by encouraging surface sampling that confirmed a gossan identified by Placer (1% Ni, 0.11% Cu, 64ppb Pt and 95ppb Pd) and historic percussion and RC drilling with reported intersections of 16m @ 0.98% Ni and 770ppm Cu (Poseidon Exploration) and 26m @ 1.65% Ni (Placer, (reported in Marston, 1984)) in the weathered zone. Recent RAB drilling of this area by Lodestar reported a best intersection of 27m @ 1.29% Ni and 680ppm Ni from surface (maximum 2.59% Ni).
- Mount Marion North - A review of Dioro's gold exploration database revealed a Cu anomaly in soils above the ultramafic sequence. The area was selected for the second phase of EM surveying. A moving loop EM survey identified a number of conductors on the eastern and western margins of the ultramafic sequence; two have been tested by deep RC drilling. The eastern target was identified as sulphidic black shale on the contact of the ultramafic; the western target was identified as dolerite and gabbro bearing disseminated sulphides. The sulphide zone is believed to be associated with a complex zone of north east trending, overlapping conductors located on the western margin of the ultramafic sequence. The conductors, extending over a strike length of 500m, have not been effectively tested by drilling.
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| Interpreted geology over CH30 EM image | Interpreted geology over auger sampling (Cu, ppm) |
- The third area is located on the eastern margin of the project, north of the Wildcatters nickel mineralisation. A moving loop EM survey was completed over Location 51, targeting the strike continuation of the Wildcatters ultramafic sequence. The survey identified a weak to moderate conductor located in the northern third of the survey area, on the eastern contact of the ultramafic sequence. Historic drilling intersected black shale in this position to the north of the conductor. Lodestar completed a program of RAB drilling and confirmed the presence of a black shale unit coincident with the conductor. Elsewhere in the eastern part of the project there has been little systematic drill testing of the ultramafic sequences which are generally fault-bound, narrow, strongly sheared and metamorphosed.