Previous exploration has identified copper, lead, zinc, silver and gold mineralisation at the Eastman Prospect. This oxidised copper-enriched zone of outcrop has been identified by geologists as being 25-50 metres wide and 300 metres long at the surface. A shale horizon with inter-beds of banded iron-formation (the “southern BIF”) outcrops immediately to the north.
The Eastman prospect consists largely of layered sequences of disseminated sulphides which displays some of the characteristics of VMS base metal deposits, including distinctive patterns of metal zonation, the presence of magnesian alteration and an association with exhalative horizons (BIF, chert-carbonate rocks). The mineralization remains open to the west. The morphology of the mineralisation is not well understood.
Newmont Pty Ltd drilled one diamond hole at the Eastman prospect in 1969, confirming supergene copper-zinc-lead-mineralisation intersected in previous percussion drilling. In 1971 and 1972 Kennecott exploration (Australia) Limited (Kennecott) drilled five diamond drillholes up to a depth of 165m. The drilling intersected an overturned sequence of altered volcanogenic rocks and sediments dipping steeply to the south. Disseminated copper, lead and zinc sulphides, hosted by altered volcanic rocks, were intersected in holes DDH1 and DDH3 located 240m apart. The best intersection was reported as 0.75m at 7.7% Zn, 3.1% Pb and 121g/t Ag (DDH1)4.
Between 2004 and 2006 10 RC holes totalling 1,638m and 1 diamond drill hole, totalling 335m were drilled. The RC drilling returned the best two intersections which were reported as follows:
Drill Hole ERC 56:
5m @ 5.76g/t Au, 45.7g/t Ag, 0.9% Cu, 56.7% Pb and 5.8% Zn from 125m including 2m @ 13.50g/t Au, 99.5g/t Ag, 1.7% Cu, 13.8% Pb and 9.0% Zn from 127m
Drill Hole ERC 57:
7m @ 50.58g/t Au, 35.2g/t Ag, 1.2% Cu, 2.3% Pb and 3.4% Zn from 118m including 1m @ 2.48g/t Au, 87g/t Ag, 3.2% Cu, 7.5% Pb and 10.1% Zn from 123m
Peako conducted Gradiant Array and Dipole-Dipole Induced Polarisation (IP) Surveys at the Eastman prospect in late 2018. Discrete GAIP and DDIP chargeability anomalies were detected on and along strike of the known mineralisation.
A GAIP and DDIP chargeability anomaly high, with approximate maximum amplitude of 5.6 msec, is closely correlated with the shallow Cu-Zn sulphide mineralisation at the Eastman Prospect, thereby confirming that the IP survey method successfully detected known mineralisation. A discrete and subtle resistivity anomaly high agrees with a previous description of a resistive silica cap occurring at the top of the Eastman gossan .
A well pronounced GAIP chargeability anomaly high of 6.5 msec is located along strike to the west of known Eastman mineralisation, and this feature has been named “Eastman West”. The Eastman West GAIP anomaly has not been tested by existing drilling. A follow-up DDIP traverse over this GAIP anomaly confirmed its source is likely to be shallow, and also provides an additional IP chargeability target response extending down dip to the south of the GAIP anomaly response.
The Eastman West IP anomaly zone may form a westerly plunge extension of Eastman mineralisation. Historical drillhole DDH05 was close to testing the Eastman West GAIP chargeability anomaly, but this drillhole was drilled parallel to the dip of the IP anomaly, and had very poor recoveries. As a result, it was not assayed.
The Eastman West IP anomaly responses provide a direct base metal target zone in close proximity to, and along strike of, the known Eastman Cu-Zn mineralisation. New deep drilling is required to determine the source of the Eastman West GAIP and DDIP chargeability anomalies.
A seperate large GAIP chargeability anomaly was identified at the South-West corner of the GAIP survey area and, despite extension of the survey, has not been closed off.
Peako has planned a number of drill holes to test the anomalous IP responses identified at the Eastman Prospect which are not explained by existing drilling.