Kalgoorlie Gold Mining has returned to its flagship Pinjin gold project 140 kilometres northeast of Kalgoorlie, with a reverse-circulation (RC) rig now spinning the drill bit at its Lighthorse prospect. Drilling at Lighthorse will continue alongside an aircore program at the company’s adjacent Laverton Tectonic Zone (LTZ) Flexure target which is more than halfway complete and on budget.
KalGold says the RC drilling began during the weekend after the rig mobilised to site on Friday. Up to 19 holes for 3200 metres are planned across Lighthorse, where previous work has shown the primary gold system is bigger than first thought and remains open to the north.
The latest program is designed to tighten its RC drill-hole spacing to about 50m by 40m across the northern Lighthorse area and add extra infill and extension holes around earlier RC coverage. It will also test, for the first time with RC drilling, the northern extension of a north-south magnetometric conductivity (MMC) anomaly picked up in KalGold’s 2025 sub-audio magnetics (SAM) survey.
A magnetometric conductivity survey – such as SAM – uses electrical currents passed through electrodes in the ground to create secondary magnetic fields, which are then measured to help map changes in electrical conductivity below surface. By contrast, a conventional magnetic survey measures passive variations in the Earth's natural magnetic field caused by changes in the magnetic susceptibility, or iron and mineral content, of subsurface rocks.
All of the RC holes are being drilled at a 60-degree dip to the east to best intercept the steeply west-dipping structures which are characteristic of that part of the mineralised corridor. The program is expected to take about three weeks.
Simultaneously, KalGold’s first-pass 10,750 metre aircore drilling is continuing across the LTZ Flexure target area, about 3.5km south-east of the Kirgella Gift-Providence deposits. About 140 holes have been completed so far, representing an estimated 55 per cent of the planned program, with hole depths averaging about 35m against a pre-program estimate of 50m.
KalGold says the shallower drilling means the program is tracking positively against budget, although hole depths are expected to increase southwards towards the Lake Rebecca palaeodrainage system.
Early geology defined from the aircore work is lining up with the company’s interpretation of the flexure, where the boundary between mafic-ultramafic rocks to the west and Rebecca Sequence rocks to the east is marked by shearing, quartz veining and several alteration styles.
Those geological associations are important. With rocks more greatly stressed in the region of the flexure – a fold in the geological sequence – rock units tend to slide past one another and create shears and voids parallel to bedding which, when combined with joints or faults opening perpendicular to bedding, can provide pathways for mineralising solutions and point to the possible existence of a mineralised conduit.
The LTZ is one of WA's most prolific gold-mineralised structures. It is a major 250-kilometre-long, deep-seated structural corridor within the Eastern Goldfields Superterrane of the state's Archean-aged Yilgarn Craton. It ranks second only to the Kalgoorlie region for gold endowment, having hosted more than 30 million ounces of gold production and several multi-million-ounce deposits.
The company’s early July 9 announcement flagged its broader LTZ Flexure aircore push, comprising up to 225 holes on widely-spaced 320m by 80m lines, designed to detect near-surface gold and pathfinder anomalism which could be followed up by RC drilling.
The company’s June quarterly report showed its campaign in the Pinjin area sits in a busy pipeline, with assays still outstanding from 21 RC holes for 3702m completed in late May at Kirgella Gift and Providence, and deeper diamond drilling beneath that deposit corridor pencilled in for the September quarter.
KalGold’s total inferred gold resource currently stands at 214,300 ounces, including 76,400 ounces at Kirgella Gift and Providence and 137,900 ounces at La Mascotte.
With the Lighthorse RC rig chasing extensions, the LTZ Flexure aircore program opening up the possibility of new targets and further assay results still to land, KalGold has plenty of Pinjin newsflow stacked up for the weeks ahead. Being positioned in one of Australia's premier gold corridors only adds to the prospectivity.
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By Doug Bright
