Octava Minerals has found 14 key structural antimony targets along a 10-kilometre antimony corridor at its Yallalong project in WA’s Gascoyne region, that were identified via a recent surface gravity geophysical survey.
The targets look similar to its Discovery prospect that was the only site drilled out of four prime areas identified in historic exploration, and which went up to 7m at 3.27 per cent antimony along a 300m strike.
The critical metal has sent the hearts of ASX punters racing over the past four months, with demand leaping after the Chinese government put primary and secondary bans on antimony exports to the United States.
Though it has a range of uses, antimony is particularly noted for its use as a hardening agent for ammunition and in other defence sector applications.
China is the world’s biggest antimony, producing 40,000 tonnes annual or 48 per cent of global production - Australia is the largest exporter of the silver-grey metal, pumping out 21.7 per cent of global exports in 2022.
Octava undertook its gravity survey to establish some important geological parameters that are recognised globally as key factors in hosting antimony mineralisation.
Such factors typically include the existence of faults and shears as plumbing systems for mineralising fluids and proximity to significant rock boundaries.
Such locations often represent heat or fluid sources or geochemical modifiers and buffers and can themselves be planes of faulting or shearing.
Octava says the survey results, when combined with the outcomes of limited historic drilling, have redefined its exploration model for high-grade antimony at Yallalong and that the 14 new targets are being lined up for systematic drilling.
Octava Minerals’ managing director Bevan Wakelam said: “The new gravity data redefines the exploration model for high grade antimony at Yallalong. It explains the presence of anomalous antimony along the structural corridor and predicts potential hot spots along it. It is exciting to consider the possibility of a continuous system extending under cover for more than 10km and having a method to pinpoint the most prospective zones.”
A preliminary structural analysis of the gravity data was undertaken in concert with magnetic and radiometric geophysical data.
The interpretation indicates that high-grade antimony mineralisation at Discovery and its three other historically defined companion targets appear to correlate with multiple late northwest-southeast shear sets.
These structures offset the north-south-trending stratigraphy and other structures and appear to be tensional linking shears between two - or possibly four - major north-south linear faults set about 750m apart which might open up depositional sites at shear junctions.
Antimony has been known since ancient times. It is sometimes found free in nature but is usually obtained from the ore's stibnite (antimony sulphide) and valentinite (antimony oxide).
Very pure antimony is used to make semiconductor devices, such as diodes and infrared detectors and can be alloyed with lead to increase lead's durability, such as in wheel balance weights.
Antimony alloys are also used in batteries, low friction metals, type metal and cable sheathing, while antimony compounds are used to make flameproofing materials, paints, ceramic enamels, glass and pottery.
The ancient Egyptians used antimony, in the form of stibnite crystals, for black eyeliner.
The latest 14 targets, now assigned primary and secondary target status, also appear to share similar structural locations that persist along a 10km strike corridor, principally between the major north-south linear structures.
Ground gravity data was acquired by Atlas Geophysics under the supervision of external geophysical consultancy NewGen Geo Pty Ltd.
The company says recent sand and detrital cover at Yallalong frustrates detailed geological interpretation of magnetics data.
As work develops, surface geological mapping could be assisted by a detailed program of on-ground mapping or shallow bottom-hole geological logging of rotary air blast or air-core drill holes, which could also double as a shallow bottom-of-hole geochemical program.
With a swag of 19 targets at hand and interpretations no doubt still being refined, the company looks like it might have the rig onsite for quite a while.
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By Doug Bright
