Large, Strong Conductors Identified Off Both Drill-Holes; Assays Indicate Potential VHMS System
Strong Offhole Conductors at Oval
Perth, Feb 17, 2025 AEST (ABN Newswire) - Great Western Exploration Limited (
ASX:GTE) is pleased to announce results from the down-hole electromagnetic survey (DHEM) and assays from the first phase of diamond drilling at the Oval Copper-Gold Target in Western Australia.
Key Points
- Results from assays and the down-hole electromagnetic survey (DHEM) for the first two holes drilled at Oval have been returned, with two large, strong conductors modelled below each drill-hole, with one just 50m below one of these holes.
- Each of the modelled conductor's geophysical signature is interpreted to have high prospectivity for massive sulphide accumulation.
- While no stand-out copper-gold assay drill results were received, pathfinder assay results identified multiple prospective horizons, that are interpreted to be close to a potential major mineralisation system/s.
- Great Western interprets the conductors' stratigraphic position within the Yerrida Basin Sequence represents a Volcanic Hosted Massive Sulphide (VHMS) copper-gold mineralisation system, similar to the DeGrussa Copper-Gold Deposit in the adjacent Bryah Basin.
- The position of the conductors at Oval is considered by the Company to be located in a prime position for development of a major mineralisation system, due to their location on the fertile, crustal- scale Ida Fault, that's cross-cut at this location by a basin defining "growth fault".
- As a result of this development, Great Western plans to commence drilling by either extending or wedging from drill-hole 24GOVDD001 and test the interpreted VHMS style conductor target below this hole immediately after access has been reestablished due to recent cyclonic activity in the region.
- Great Western has a strong cash position of $4.7 million (31 December 2024) and is well-funded for its forthcoming exploration programmes.
The Oval Copper-Gold Target is located within the Company's Yerrida North Project, located on the northern and western portions of the Yerrida Basin. The target is approximately 800km north-east of Perth and adjacent to the DeGrussa and Monty Copper-Gold Volcanic Hosted Massive Sulphide deposits (VHMS), shown in Figure 1*.
Assays and geophysics results have been returned for the first phase of drilling at the Oval Copper-Gold Target.
These results have allowed Great Western to further define a large and prospective interpreted copper-gold mineralisation system. One of the potential zones of copper-gold metal accumulation is interpreted to be just 50m from the bottom of drill-hole 24GOVDD001 (see Figure 2*).
Interpretation of the data received to date has concluded the potential mineralisation system identified is large and complex, with geophysical modelling of the DHEM survey data defining two large, strong conductors. The Company's geophysical consultants advised that both interpreted conductors' geophysical signature has high prospectivity for massive sulphide accumulation.
While assay results did not return significant copper-gold results, interpretation of pathfinder elements suggested a position close to a copper-gold mineralisation system, with a similar signature to the nearby DeGrussa Copper- Gold Deposit. The Company interprets that the assay results support the high prospectivity of the modelled conductor and plans to commence drilling immediately after access has been reestablished due to recent cyclone activity.
Technical Discussion
The analysis, interpretation, and modelling of the DHEM data was undertaken by experienced geophysical consultants Newexco Exploration, who modelled a large, strong conductor located approximately 50m below drillhole 24GOVDD001 (Figure 2*). A second and deeper conductor was also modelled below drill-hole 24GOVDD002, located 1.5km west of 24GOVDD001 (Figure 3*), with both conductors potentially connected.
A subsequent Fixed Loop Electromagnetic survey (FLEM) was completed to supplement and further refine the conductors' position and orientation, with both plates interpreted to have a relatively flat dip. Newexco noted that the geophysical signature of both conductors has high prospectivity for accumulation of massive sulphide.
The Company interpreted that the interbedded dolerite/basalt with siltstone rocks observed in both drill-holes belong to the Killara Formation. Previous work has proposed that the Killara is the equivalent to the DeGrussa Formation in the adjacent Bryah Basin, which is host to the DeGrussa VHMS copper-gold deposit (Hawke et al, 2015). Further, geological textures and alteration of the rock units observed in drill-core was interpreted by Great Western to support a DeGrussa Style VHMS copper-gold mineralisation model.
Great Western engaged prominent industry geochemist Dr Carl Brauhart of Camp Oven Exploration, to assist with interpretation of the drill assay results. Dr Brauhart experience includes working on the DeGrussa VHMS deposit hosted in the adjacent Bryah Basin. Dr Brauhart completed litho-geochemical analysis of the drill assay data to define and classify lithological units and associated alteration, and propose a potential mineralisation model. Drill core was reviewed to verify these interpretations.
Dr Brauhart's assessment support's the Company's proposed VHMS model, finding:
- Analysis of Rare Earth and immobile elements from the intersected mafic rocks indicate formation in a subduction-related setting; prospective for VHMS mineralisation;
- There are several discrete sedimentary horizons with VHMS pathfinder co-enrichment: Cu-Au-Bi-S-Zn-As-PbAg-Te-Sb-In. This is consistent with a distal location from a VHMS "black smoker chimneys" system, with multiple horizons throughout the drill-hole with this pathfinder signature. Further, the absence of co-enrichment in elements Mo, V, U, and Ni suggests that the metal enrichment is not that of common black shale;
- The analysis found varying degrees of albite-chlorite-illite-muscovite alteration, consistent with that developed around VHMS deposits; and
- Litho-geochemical analysis identified six "families" of mafic volcanic rocks and two separate sedimentary units, indicating a dynamic volcano-sedimentary environment, further supporting a potential VHMS mineralisation system.
Based on this supporting evidence, Great Western interprets that the modelled DHEM plates represent a highly prospective DeGrussa Style VHMS target. The Company also interprets the first two holes intersected multiple horizons of potential VHMS mineralisation at a distal position from the main metal hosting vent, with the defined conductors interpreted to represent the main mineralisation zone of one of these potential VHMS formations (Figure 5*).
As detailed, multiple geological attributes supports the defined conductor representing a DeGrussa Style VHMS mineralisation system, summarised below:
- Both modelled DHEM conductors are highly conductive, and is interpreted by Newexco to be highly prospective for massive sulphide accumulation;
- The drilled geological units and associated textures and alteration (the latter supported by geochemical analysis) supports a VHMS mineralisation environment;
- Mafic volcanic trace element data indicates a subduction-related formation setting prospective for VHMS mineralisation;
- VHMS pathfinder co-enrichment (Cu-Au-Bi-S-Zn-As-Pb-Ag-Te-Sb-In) on discrete sedimentary horizons in both drill-holes indicates multiple possible fallout zones from adjacent VHMS "black smokers";
- The volcanic and sedimentary rocks intersected are interpreted to be part of the Killara Formation, where previous work indicating this package is the stratigraphic equivalent of the DeGrussa Formation (Hawke, 2016), host to the DeGrussa Copper-Gold VHMS Deposit;
- Airborne gradiometry gravity highs (Figure 4*) are coincident with the DHEM modelled conductors;
- Position of the Oval target on the crustal scale fertile Ida Fault, that is intersected by a basin defining "growth fault" (ASX announcement - Figure 1*), is regarded as a favourable position to produce a VHMS mineralisation system; and
- Position of Oval within an east-west intrusive corridor, a potential zone of weakened crust for focused metal accumulation within the Killara Formation.
Forward Programme
Drilling to test the conductor below 24GOVDD001 is anticipated immediately after access has been reestablished due to cyclonic activity in the region, by either extending or wedging from this drill-hole. The Company anticipates drilling of Oval South, Sumo Niobium, and the Juggernaut Copper-Gold Targets will commence as soon as possible after completion this second phase of drilling at Oval.
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About Great Western Exploration Limited
Great Western Exploration (ASX:GTE) is an explorer with a world class, large land position in prolific regions of Western Australia. Great Western's tenements have been under or virtually unexplored. Numerous work programmes across multiple projects are underway and the Company is well-funded with a tight capital structure, providing leverage to exploration success.
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