Special Report: The high-grade Invincible gold deposit forms the backbone of Gold Fields’ St Ives camp near Kalgoorlie.

The global miner calls it “one of the most significant discoveries in the history of St Ives, and possibly that of the Western Australian goldfields community”.

The multi-million ounce deposit almost went undiscovered.  It was only found in 2012 after Gold Fields reviewed Western Mining Corporation drilling results from the mid-90s.

The subtle gold anomalies from old air core drilling had lain dormant in the database for many years because of the low tenor gold results and small geochemical footprint.

Finding the next Invincible sized gold deposit

The Western Lefroy JV (blue) is located close to the multi-million ounce Invincible discovery (bottom left). (Supplied)

Gold Fields is now laser-focused on finding another Invincible on the 372 sq km Western Lefroy tenements with explorer Lefroy Exploration (ASX:LEX).

Gold Fields can earn up to a 70 per cent stake in Western Lefroy, adjacent to St Ives, by spending up to $25m on exploration over six years.

The JV launched a major 350-hole reconnaissance aircore AC drilling program in January this year. This wide-spaced program covers most of the tenure in Lake Lefroy using a specialised lake drilling rig.

This drilling is searching for both gold anomalies in transported cover (gravels and sands) and saprolite (oxidised bedrock) which can be used to locate the primary source in the bedrock; much like Gold Fields did at Invincible.

329 vertical air core holes totalling 16,926m have now been completed; assay results have been received and validated for a total of 273 holes.

This drilling has now reinforced two key mineralised trends at the Zanex and Eastern Shoreline prospects. The developing Eastern Shoreline trend now has a strike length, based on maximum gold in hole of 5km.

Check it out:

Drill holes completed in Lake Lefroy (coloured by maximum gold value) and the location of the Zanex and Eastern Shoreline trends, with key gold intersections. (Supplied)

These early results are significant, says Lefroy, especially given the context of the Invincible discovery which was masked underneath transported cover.

Drilling is in progress and to continue through the second quarter. Once completed, the results will be compiled and assessed with recently acquired geophysical data (gravity, magnetics).

This will provide a platform for more detailed target generation and deeper drilling – for Lefroy, this represents a step towards finding a company-making gold deposit.


This story was developed in collaboration with Lefroy Exploration, a Stockhead advertiser at the time of publishing.
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