Great Western Exploration Hits Outer Shell of New VHMS System Near DeGrussa
Key Takeaways
- Maiden RC drilling at the Seymour Target returned zinc-silver intercepts including 12m @ 0.33% Zn, 7g/t Ag from 77m and 5m @ 0.22% Zn, 2g/t Ag from 98m, interpreted as the outer margin of a new VHMS mound system.
- The copper-gold core of the interpreted VHMS system — the highest-value target — has not yet been drilled and sits between and below the two key holes, making it the primary focus of follow-up work.
- The Seymour Target sits 70km from Sandfire Resources' DeGrussa copper-gold VHMS deposit in the adjacent Bryah Basin, a globally recognised benchmark VHMS discovery.
- GTE identified this mineralisation through geological mapping and interpretation alone, without a pre-existing geophysical bullseye — a meaningful validation of the company's exploration methodology in a largely untested basin.
- The forward programme includes airborne infill magnetics, potential down-hole EM surveys, and follow-up RC drilling, with permitting being progressed as a priority before the next drill campaign can begin.
Maiden drilling at Juggernaut flags new VHMS system on the doorstep of DeGrussa
Great Western Exploration (ASX: GTE) has returned zinc-silver mineralisation from its maiden RC drilling programme at the Seymour Target within the Juggernaut Copper-Gold Project, with results interpreted to represent the outer margin of a new seafloor “mound” type Volcanic Hosted Massive Sulphide (VHMS) system. The critical hook for investors: the copper-gold core of that system has not yet been intersected.
The Seymour Target sits 70km from Sandfire Resources’ (ASX: SFR) DeGrussa VHMS copper-gold deposit in the adjacent Bryah Basin, one of the world’s benchmark VHMS discoveries. The Juggernaut project is located on the western portion of the Yerrida Basin, approximately 800km north-east of Perth.
Key assay results from the programme include:
- 12m @ 0.33% Zn, 7g/t Ag, and 0.09% Pb from 77m (drill-hole 26GJGRC006), including 1m @ 1.02% Zn from 81m and 2m @ 20g/t Ag from 85m
- 5m @ 0.22% Zn, 2g/t Ag, and 0.15% Pb from 98m (drill-hole 26GJGRC002)
The copper-gold core, interpreted to lie between and below these two holes, remains the primary target for follow-up drilling.
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What is a VHMS system, and why does zinc at the edges matter?
A Volcanic Hosted Massive Sulphide system forms on the ancient seafloor when superheated mineral-rich fluids (hydrothermal fluids) vent through cracks in the ocean crust and mix with cold seawater. As the fluids cool rapidly, metals precipitate out and accumulate in layered deposits directly on the seafloor. The result is a “mound” of stacked mineralisation, with different metals concentrating at different temperatures and distances from the vent.
Reading the mineralisation signature
Think of a VHMS mound like a target with concentric rings. The hottest zone sits closest to the vent and is enriched in copper and gold. Moving outward, as temperatures drop, the mineralisation transitions to zinc, lead, and silver. This zoning is predictable and well-documented across VHMS deposits globally.
The geochemical signature recorded at Seymour, a Zn-Ag-Pb-Cd-S +/- Tl fingerprint, is characteristic of the outer, cooler margins of this style of system. In the schematic diagram of a VHMS mound (Figure 3 in the announcement), the outer zone is represented by “black ore” rich in zinc, lead, and silver, while the hotter inner core is represented by “yellow ore” enriched in copper. The Seymour intercepts, as annotated in that figure, plot in the outboard position relative to the interpreted copper core.
Two additional geological features support this interpretation. First, the drilled intercepts contain 1–5% sulphide mineralisation within the host rocks, a positive indicator of a fertile VHMS system rather than a barren zone. Second, and critically, these intercepts were recorded at a shale-mafic volcanic rock contact, the ideal geological boundary for mound-type VHMS development.
GTE interprets the high-temperature copper-gold core to lie between drill-holes 26GJGRC002 and 26GJGRC006, and below the current drilled depth. That gap between the two holes is precisely where follow-up drilling is now being prioritised.
Why Seymour is a genuine discovery-stage opportunity
The Yerrida Basin remains largely untested for VHMS
The Yerrida Basin is geologically similar to and of comparable age to the Bryah Basin, the basin that hosts both DeGrussa and the Monty copper-gold VHMS deposit. Despite this geological kinship, very little systematic VHMS exploration has been conducted in the Yerrida.
What makes the Seymour result particularly notable is the absence of a clear discrete geophysical or surface geological target guiding the maiden programme. GTE defined a new potential VHMS system through sustained geological mapping, interpretation, and modelling alone. Finding mineralisation interpreted as part of a VHMS system in a maiden campaign, without a pre-existing geophysical bullseye to aim at, is a meaningful validation of the company’s systematic exploration methodology.
The copper-gold core is the next target
The cross-section interpretation (Figure 4 in the announcement) illustrates how the two key drill-holes are interpreted to have intersected opposite edges of the same stratigraphy, which appears to be folded. This geometry places the highest-priority copper-gold target in the zone between and below 26GJGRC002 and 26GJGRC006.
GTE’s planned next steps are:
- Airborne infill magnetics survey planned prior to and concurrently with drilling
- Potential down-hole EM survey planned to further refine the mineralisation model
- Follow-up RC drilling targeting the zone between 26GJGRC002 and 26GJGRC006, plus extensions north and south (Figure 5)
- Permitting being progressed as quickly as possible
- Geophysical surveys to be undertaken concurrently to optimise drill targeting
Baroo: a secondary copper target also advancing
The Baroo Target, identified during earlier regional geological mapping and rock-chipping, was also tested in this programme. Two shallow RC holes intersected a quartz vein below surface, returning 1m @ 0.2% Cu from 24m (26GBBRC002) and 1m @ 514ppm Cu from 25m (26GBBRC001).
The results are modest, but GTE interprets the width and tenor of copper mineralisation to increase at depth below the drilled intercepts. Further drilling is planned concurrently with Juggernaut follow-up. Seymour remains the primary story; Baroo is a secondary thread worth watching.
Key results at a glance
| Drill Hole | Target | From (m) | Interval (m) | Key Grades |
|---|---|---|---|---|
| 26GJGRC006 | Seymour, Juggernaut | 77m | 12m | 0.33% Zn, 7g/t Ag, 0.09% Pb |
| 26GJGRC006 (incl.) | Seymour | 81m | 1m | 1.02% Zn |
| 26GJGRC006 (incl.) | Seymour | 85m | 2m | 20g/t Ag |
| 26GJGRC002 | Seymour, Juggernaut | 98m | 5m | 0.22% Zn, 2g/t Ag, 0.15% Pb |
| 26GBBRC002 | Baroo | 24m | 1m | 0.2% Cu |
All reported intervals are downhole lengths. True widths are not yet known at this stage of exploration.
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What’s next for Great Western Exploration
The focus now shifts to permitting and geophysics. GTE has stated it is moving as quickly as possible to secure the permits required for follow-up drilling at Seymour, with that permitting being progressed as a priority. A market update is expected once permitting is completed.
The forward programme, in sequence, is:
- Permitting for follow-up drilling at Seymour progressing as a priority
- Airborne infill magnetics and potentially down-hole EM surveys prior to and concurrent with drilling
- Follow-up drill targets defined between and around 26GJGRC002 and 26GJGRC006, plus along-strike extensions north and south
- Baroo follow-up drilling planned concurrently
- Market update to follow once permitting is completed
No resource estimates have been defined at this stage, and no timelines beyond the permitting and survey sequence have been disclosed.
GTE’s Oval Copper-Gold Target, tested through diamond drilling as a separate programme, returned preliminary observations consistent with a significant copper-gold system, adding another thread to the company’s expanding discovery pipeline across its Yerrida Basin tenure.
The geological logic here is straightforward: GTE has found the outer shell of what is interpreted to be a new VHMS system in its very first drilling campaign at Seymour, conducted without a pre-existing geophysical target. The company holds a prominent tenement package over the largely underexplored Yerrida Basin, a basin considered geologically similar to and of comparable age to the Bryah Basin, host to both DeGrussa and Monty. The copper-gold core interpreted to lie between and below the current holes is the prize that the next phase of work is designed to test.
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