Gateway Mining has delivered the first drilling confirmation that its Great Western prospect at the Yandal gold project in Western Australia hosts a large-scale gold-silver hydrothermal system, with maiden drilling defining a gold-mineralised structure stretching four kilometres along a key geological contact at the Great Western flexure zone.
The company believes shallow aircore drilling has only scratched the surface of a much larger opportunity. The broader hydrothermal system can now be traced for 10 kilometres of strike, giving geologists their best indication yet of the scale of the opportunity emerging at Great Western.
Notably, the drilling confirmed gold mineralisation along the sheared contact between a differentiated dolerite unit and intermediate volcanic rocks, the geological setting Gateway has long argued is the key control on mineralisation at Great Western.
The best gold result from the campaign was a bottom-of-hole intercept of 1m at 2.5 grams per tonne (g/t) gold from 36m.
Management says the standout feature is the clear geochemical zonation, which may provide a strong pointer to primary gold mineralisation at depth.
Unexpectedly high-grade silver hits have added an intriguing twist to the story, appearing to form an outer halo around the main gold target. Results included 1m at 89g/t silver, 1m at 78g/t silver, 1m at 72g/t silver, 1m at 52g/t silver and 1m at 46g/t silver.
Management says, importantly, the drill bit was still in the mineralised zone when most holes finished, with nearly all the colour showing up at the bottom of the shallow aircore holes, averaging just 20m in depth along the target structure.
Intense silicification and poor penetration of the harder dolerite prevented the lighter aircore rigs from drilling deeper, suggesting the primary mineralisation remains largely untested.
Because only the final metre of the silver-bearing holes was analysed for multi-element chemistry, management believes the silver zones may prove more extensive than currently reported.
High-grade silver is rare in the Eastern Goldfields and may point to the substantial hydrothermal plumbing system management believes sits beneath Great Western.
What is particularly exciting is the clear geochemical zonation we are seeing – a gold-dominant core (the flexure zone) with high-grade silver anomalism appearing distally and outwards from the main gold core. This style of zonation is especially characteristic of low-sulfidation epithermal systems and provides us with a strong vector towards the primary gold mineralisation.
Great Western was already regarded as one of Gateway’s highest-priority targets before drilling began, with mapping, soil sampling and hundreds of gold nuggets pointing to what management described as a textbook dolerite-hosted gold system.
The latest results have strengthened that view and drawn comparisons to the Golden Mile, where gold is concentrated along sheared dolerite contacts and silver occurs in outer structural zones.
Great Western is the latest addition to Gateway’s growing Yandal discovery pipeline, joining Cowza, Celia South, Haflinger, Hummer, Mustang and Rubicon. The broader project hosts an existing gold resource of 400,000 ounces in WA’s northern Goldfields and near Northern Star Resources’ giant Jundee operation.
Gateway ended the March quarter with $15.7M in cash and $5.6M in liquid securities, leaving it well funded for the next phase of drilling.
Management is now escalating its exploration efforts, with a reverse-circulation (RC) rig arriving on site this week to begin the first deep test of the system. Drilling will target fresh rock along the gold-bearing dolerite contact and beneath the high-grade silver anomalies, where management believes the primary gold mineralisation may be concentrated.
A second RC rig is expected early next quarter to accelerate the program. Management expects a rapid flow of RC results, with assay turnaround targeted at about two weeks.
Market watchers will likely be keeping a close eye out for the first RC holes to see whether the silver anomalism leads into a significant primary gold system at depth. If it does, Great Western could emerge as the next major discovery front within Gateway’s district-scale Yandal gold story.
Is your ASX-listed company doing something interesting? Contact: matt.birney@wanews.com.au
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