Alderan’s exploration at Frisco in 2017 identified the Perseverance prospect, a large 2.5km diameter chargeability feature consistent with a large mineralised porphyry copper system.
Perseverance is between the Cactus Corridor, which hosts the Cactus mine, and the large Accrington skarn, which hosts historic mines and large outcropping copper-zinc skarns.
In a mineralised porphyry system, high chargeability zones often represent pyrite-rich zones of alteration. High chargeability and low resistivity (i.e. more conductive) features may also represent other styles of mineralisation in the distal parts of the porphyry system and can host higher grade deposits.
FR18-003 (previously called ALIM003) was designed to test the large Perseverance chargeability and coincident resistivity anomaly which was interpreted to represent a pyrite-rich shell associated with a mineralised porphyry system (refer to announcement “Drilling Commences on Large Copper Skarn & Porphyry Targets” 18 June 2018). The hole was completed in July intersecting skarn (0m to 66.15 and 178.8 to 184.8m) and monzonite intrusive from 66.15 to 178.8m and from 184.4m to end of hole at 1016.3m.
Pyrite mineralisation was intersected as disseminations and patches of up to several percent often associated with shear zones within the weakly chlorite altered monzonite Cactus stock intrusive with pyrite increasing from 844m to the end of the hole at 1016.3m. Minor trace copper mineralisation was noted to 804m. Assays did not return any significant mineralisation.
Mineralisation intersected in FR18-003 is unlikely to have been sufficient to explain the large Perseverance chargeability anomaly. The increase in pyrite to end of hole, suggests that the main source of the anomaly may be deeper than the final hole depth (1016.3m). Given the presence of stronger alteration and historical intercepts of copper-molybdenum mineralisation within potassic altered intrusive in the Cactus Canyon area, the focus for future porphyry copper exploration is likely to focus on the northern Cactus Canyon area.