The start of a maiden 10-hole diamond drilling program by Sultan Resources (ASX: SLZ) has confirmed the porphyry potential of the Big Hill copper-gold target in New South Wales.
The first three holes for 1,135.8m targeted a prominent induced polarisation (IP) chargeability anomaly reported in April, which lies within a magnetic low and is coincident with low-level soil geochemical anomalism.
Drilling aimed to confirm the relationship between the anomaly and a pyrite ‘halo’ and provide three-dimensional geological information to guide the remaining seven holes towards achieving a significant mineralised intersection.
IP chargeability anomalies can represent broad zones of disseminated sulphides such as pyrite in an alteration ‘halo’. While not always coincident with economic concentrations of copper-gold mineralisation, they may indicate a system is present.
Big Hill is greenfields territory for Sultan, with no previous drilling on record.
The company said the maiden holes would be “truly exploratory” in nature.
Sultan’s work at Big Hill intersected porphyry-style alteration with disseminated pyrite, trace chalcopyrite and bornite, believed to be sitting in the distal parts of an alkalic porphyry copper-gold system.
It confirmed the targeted IP chargeability anomaly is caused by pyrite, giving sufficient vectors for further drill targeting within the larger Big Hill magnetic complex.
The complex has features similar to alkalic porphyry copper-gold systems at the Cadia and Boda discoveries, including coincident magnetic and IP anomalies, complimentary low-level soil geochemical pathfinder anomalies, outlying high-grade rock chip results, and drilled porphyry-style alteration, veining and disseminated sulphides.
Sultan managing director Steve Groves said the early results were “extremely encouraging” for the remainder of the drilling program.
“Geological results from the first three holes have been extremely encouraging and indicate that we are in the distal alteration halo of a potential buried alkalic porphyry copper-gold system,” he said.
“The style and intensity of alteration varies from hole to hole and will allow us to start constructing vectors towards the possible causal intrusion and potential wallrock zones of [the] elevated mineralisation.”
Based on the early results, Mr Groves said the company would evaluate the potentially-related, outcropping Razorback copper-gold skarn target for shallow reverse circulation drill testing.
It will finalise a drilling approach once approvals and permits are in place, and contractors have been secured.