Shallow Copper Oxides Interpreted Over Up To 1.5 Sq. Km
AusQuest Limited (ASX: AQD) has received additional encouraging assay results from its recently completed Reverse Circulation (RC) drilling programme at the Cerro de Fierro Copper Prospect in southern Peru, under the company’s Strategic Alliance Agreement (SAA) with a wholly-owned subsidiary of South32 Limited.
The programme, which comprised 15 RC drill-holes (for 5,048m), was successful in locating near-surface extensions of the copper mineralisation that was previously discovered at depth (~150m to 300m) during earlier drilling programmes to the north, as well as strong indications of nearby porphyry copper mineralisation.
Managing Director, Graeme Drew, said that while the extent, thickness and grade of the shallow copper oxide mineralisation is not fully known at this stage, the possible extent of the mineralised horizon appears to be extensive (up to 1.5 sq. km), subject to further drilling and/or sampling to confirm the continuity and grade of the copper within the potential target area.
Five of the 15 widely-spaced drill holes intersected shallow copper oxides (at depths <50m) with thicknesses varying from ~20 to 30 metres and average copper grades ranging from ~0.13% Cu up to ~0.57% Cu with associated silver values from ~1.0g/t Ag and up to 9.0g/t Ag.
Mr Drew said interpretation of the drilling results and topographical data demonstrates a strong relationship between anomalous copper values and topography. Four drill-holes (CDFRC 03, 05, 08, 010) were found to be located within valleys below the copper-bearing horizon and, consequently, did not intersect the shallow copper oxides, while six drill-holes were located outside the limits of the mineralisation.
A large potential copper target area has now been outlined after compiling both the drill-hole and surface rock-chip sampling data, which show a clear relationship between anomalous copper at surface (copper values from 200ppm up to >1.0% Cu) and topographical relief.
Mr Drew said further drilling of this shallow copper oxide horizon is required before any meaningful resource calculations can be made.
Assay results from the RC drilling programme also provided strong evidence for nearby porphyry copper mineralisation located either lateral to, and/or beneath, the current level of drilling.
Thick zones (>80m) of strong advanced argillic alteration (lithocap) were intersected below the copper oxide layer in eight of the RC drill-holes. Multi-element geochemical analysis of these zones identified pathfinder elemental associations (Mo, W, Te, Bi) and vectors that suggest the drill-holes are close to the base of a lithocap and, by definition, close to potential porphyry copper mineralisation.
Mr Drew said the delineation of a potentially large, shallow copper oxide exploration target together with clear vectors to one or more porphyry targets in the vicinity, had further enhanced the potential at Cerro de Fierro.
“While the recent drilling has delivered some highly encouraging results, we still need to do more work to fully understand its implications,” he said.
“The presence of shallow copper oxide mineralisation over an extensive area is an encouraging development for the prospect and, together with the strong indications of porphyry copper mineralisation, has added a new dimension to the project on top of the manto-style (IOCG) copper mineralisation that was intersected by earlier drilling programs to the north.
“How all this ties together is still a work in progress but the variety and extensive nature of copper mineralisation in the area has provided us with a strong belief that further copper discoveries will be made” he added.
