AusQuest’s latest CSAMT survey has outlined an interpreted porphyry copper footprint at least 2.5km by 1km at Cangallo in southern Peru. The geophysics also points to untested targets at depth and two possible additional porphyry centres, although none has yet been confirmed by drilling.
- Interpreted Cangallo porphyry footprint of at least 2.5km by 1km
- Deep resistivity targets identified north and south of known mineralisation
- Two additional target areas detected east and west of the main system
- Follow-up drilling depends on Stage 4 permits expected shortly
- Diamond drilling and assays continue below the current RC depth limit
CSAMT survey expands the interpreted Cangallo footprint
AusQuest Limited (ASX:AQD) has used a new geophysical survey to sketch out a Cangallo porphyry copper system substantially larger than the ground tested so far. Controlled Source Audio-frequency Magnetotelluric data indicate an interpreted mineralised footprint of at least 2.5km by 1km, with substantial areas still untested by drilling.
The result extends the exploration story around Cangallo, where recent drilling extended Cangallo copper mineralisation to about 800 metres depth and identified higher-grade zones. The new survey does not add copper assays or establish a mineral resource; it provides a resistivity model intended to guide where the next holes should go.
Deep anomalies create new drilling priorities
Quantec Geoscience’s CSAMT work identified low-resistivity zones at depths beyond 500 metres, both north and south of the currently defined copper mineralisation. AusQuest interprets these anomalies as possible areas of stronger alteration associated with untested porphyry centres, but that interpretation remains to be tested.
At shallower levels, the company says low resistivity appears closely associated with alteration and copper mineralisation, while higher-resistivity zones may represent quartz diorite intrusions, some mineralised and some unmineralised. Surface mapping and rock-chip sampling are described as supporting the relationship between anomalous copper and the lower-resistivity zone.
Two eastern and western targets point to a possible porphyry cluster
The survey also found similar resistivity patterns east and west of the known system, persisting from roughly 100 metres to 500 metres depth. Target Area 1, east of a regional NNW-trending fault, could represent another porphyry centre. It is largely hidden beneath sedimentary and volcanic cover, although small quartz diorite outcrops containing pyrite provide some geological support for the interpretation.
Target Area 2 lies west of the known mineralised porphyry and contains a several-hundred-metre-thick low-resistivity zone that may reflect more intense alteration. AusQuest says both areas will be included in future exploration programs, raising the possibility of a broader cluster of porphyry deposits rather than a single isolated system. That remains a geological hypothesis, not a confirmed discovery.
Drilling remains the test of the geophysical model
Follow-up drilling into the northern, southern, eastern and western targets is planned once Stage 4 permits are received, which the company expects shortly. Diamond drilling is already continuing at Cangallo, targeting hypogene copper mineralisation below the approximately 350-metre depth limit of previous reverse-circulation drilling, with further assays expected over the coming weeks.
The next value-creating evidence will therefore come from the drill bit, not the colour scale on the resistivity sections. Investors will need to see whether the anomalies translate into copper mineralisation with meaningful grades and continuity, and whether the expanded interpretation can eventually support a resource estimate.
Bottom Line?
The geophysics materially broadens Cangallo’s exploration map, but permits, drilling and assays must convert interpreted anomalies into confirmed copper mineralisation.
Questions in the middle?
- When will Stage 4 permits arrive, and how quickly can drilling begin on the new targets?
- Do the deep northern and southern anomalies contain continuous hypogene copper mineralisation?
- Can Target Areas 1 and 2 prove to be separate porphyry centres rather than alteration unrelated to economic copper?