New induced polarisation (IP) geophysical data from the Apsley prospect within Impact Minerals’ (ASX: IPT) Commonwealth copper-gold project in New South Wales has helped define numerous drill targets with the potential for a major porphyry discovery.
The targets are of significant size and depth extent and were defined by chargeability and resistivity anomalies occurring within the core zone of a large soil geochemistry anomaly defined by copper-gold-platinum-palladium.
This metal assemblage is believed to be characteristic of alkalic porphyry deposits such as Cadia-Ridgeway, owned by Newcrest Mining (ASX: NCM).
Impact said the core is surrounded by a halo of zinc-lead-manganese covering several square kilometres and together these define a textbook example of a “zinc doughnut”.
Impact managing director Dr Mike Jones said the doughnut pattern is well-recognised in porphyry copper-gold exploration circles.
“These exceptional IP results, in particular the chargeability anomalies, are very exciting given they are coincident with textbook soil geochemistry patterns characteristic of those at major porphyry copper-gold deposits around the world,” he said.
“The anomalies start close to surface, extend to considerable depth and appear to link up along trend, supporting our contention that the whole area is potentially part of one large mineralised system.”
The targets have shot to the top of Impact’s priority list for a follow-up reverse circulation program over 3,000m.
Impact has already secured a drill rig, lodged paperwork for the required statutory approvals and mobilised a site team in readiness for the work program.
Field checking and rock chip sampling along the priority IP traverses along with drill site inspections for ground clearance is also in progress.
“These are now the most prospective targets in our entire portfolio and we are charging forward as fast as possible,” Dr Jones said.
“We aim to drill these compelling targets as soon as we can and we are certainly very hopeful that we could be about to find the ‘jam’ in the middle of our zinc doughnut.”
IP is a widely-used electrical geophysical technique in the exploration for porphyry copper-gold and epithermal gold deposits characterised by disseminated sulphides.
The technology identifies zones of disseminated sulphide as areas of strong electrical conductivity known as chargeability anomalies.
It can also pinpoint areas that strongly resist electrical current flow (known as resistivity anomalies) and which may for example, represent areas of strong silica alteration or intense development of quartz veins.
Impact’s IP survey comprises a total of 14 traverses, each about 2,500m long and up to 300m apart, located mostly over the core area of the major soil geochemistry anomaly.
The survey was extended several times due to ongoing encouraging results.