Exploration drilling at a remote Western Australian copper-gold project.
By Penny Langford
Solstice Minerals has reported a 148-metre copper-gold intercept beyond the current resource boundary at its Nanadie project in Western Australia, providing further evidence that mineralisation extends outside the area included in the company’s existing model.
The intercept, from hole NANRCD018, graded 0.77% copper and 0.20 grams per tonne gold over 148 metres from 201 metres depth. Australian Mining reported that most of the higher-grade mineralisation lies outside Nanadie’s current JORC Inferred Mineral Resource boundary.
The result is significant for exploration planning because it combines width, copper grade and gold credits in a step-out hole: drilling designed to test the edges of a known mineralised system rather than simply infill an area already included in the resource estimate.
It does not, however, immediately increase Nanadie’s Mineral Resource or establish that the newly intersected mineralisation is economic. Further drilling, geological interpretation, estimation work and technical studies will be required before any material can be classified as part of an updated resource, let alone an Ore Reserve.
Key figures from the Nanadie result
| Metric | Reported result |
|---|---|
| Drill hole | NANRCD018 |
| Intercept length | 148 metres |
| Copper grade | 0.77% Cu |
| Gold grade | 0.20 g/t Au |
| Intercept start | 201 metres downhole |
| Current resource | 40.4 million tonnes |
| Existing resource grade | 0.4% Cu and 0.1 g/t Au |
| Existing contained metal | 162,000 tonnes copper and 130,000 ounces gold |
The latest result compares favourably with the average grade of the existing resource, although direct comparisons must be treated carefully because a drill intercept is a sample along a hole and does not represent the grade or volume of an entire deposit.
Why the step-out hole matters
Mineral resource estimates depend on the continuity of geology and grade between drill holes. When drilling returns mineralisation beyond the interpreted resource envelope, it can change the understanding of a deposit’s scale, geometry and potential development footprint.
At Nanadie, the new intercept points to mineralisation continuing beyond the limits of the current drilling grid. That may allow Solstice to test whether the deposit extends laterally, whether higher-grade zones form coherent shoots, and whether the mineralised system remains open at depth.
The company’s project information describes Nanadie as a broad copper-gold system hosted by mafic intrusive rocks, including gabbro and dolerite, with disseminated and veinlet-style chalcopyrite mineralisation. The deposit is reported to be approximately 100 to 200 metres wide and at least 1.2 kilometres long, with mineralisation remaining open to the north, south and at depth.
The 148-metre result adds to a series of wide intercepts that have helped define the system. Earlier drilling included:
- 62 metres at 1.55% copper and 0.66 g/t gold from 256 metres, including 22 metres at 2.78% copper and 1.25 g/t gold.
- 97 metres at 0.73% copper and 0.30 g/t gold from 203 metres.
- 629.1 metres at 0.50% copper and 0.17 g/t gold from surface, including several higher-grade intervals.
These results are not interchangeable with a resource estimate, but they provide geological information about the distribution and continuity of mineralisation. The immediate question for Solstice is whether the new intercept can be linked to mineralised zones already identified inside the resource, or whether it represents a separate extension or structural repetition.
Drill samples can help define the distribution of copper sulphide mineralisation and host-rock geology.
Nanadie’s existing resource provides the baseline
Nanadie currently has a JORC-compliant Inferred Mineral Resource of 40.4 million tonnes grading 0.4% copper and 0.1 g/t gold. On the company’s published figures, that resource contains approximately 162,000 tonnes of copper and 130,000 ounces of gold.
The resource is classified as Inferred, the lowest-confidence category under the JORC Code. Inferred material is supported by geological evidence and sampling, but the level of confidence is not sufficient to allow detailed mine planning or to assume economic viability.
An updated resource could eventually include material outside the current boundary if additional drilling demonstrates sufficient geological and grade continuity. The classification of any new material would depend on the density and quality of drilling, sampling and assays, as well as the geological model and assumptions used by the competent person.
That process is separate from reporting a drill result. The intercept confirms that the drill hole encountered copper-gold mineralisation. It does not, by itself, prove the tonnage, continuity, metallurgy, mining conditions or recoveries needed to support an economic resource.
Geology and potential development implications
Nanadie is located in Western Australia’s Murchison district, near Sandstone, within a broader mining jurisdiction that hosts established gold operations and exploration infrastructure.
The mineralisation is associated with chalcopyrite, along with pyrite and pyrrhotite, in a mafic intrusive setting. Solstice has said that much of the resource is fresh-rock mineralisation below the weathered zone, while higher copper grades are associated with increased sulphide veining. Gold values can also rise where the veining becomes more pronounced.
For mine planners, a wide mineralised zone outside the current resource could eventually affect several parts of a potential development concept:
- Pit geometry: An expanded mineralised envelope could alter the size or shape of a future open-pit shell.
- Strip ratio: The depth and lateral position of any new mineralisation would influence the amount of waste that might need to be moved.
- Mining selectivity: Broad, disseminated mineralisation may be easier to mine in bulk, but grade distribution would determine whether selective mining is required.
- Processing assumptions: Metallurgical testing would be needed to establish copper and gold recoveries and concentrate quality.
- Resource confidence: More closely spaced drilling would be required to move material from Inferred into higher-confidence categories.
These are potential implications rather than established project outcomes. Nanadie has not yet been demonstrated to support a completed mining study based on the latest intercept.
Exploration beyond the current drilling grid
Solstice’s exploration strategy includes step-out drilling, resource-definition drilling and deeper holes designed to test the deposit below and around the existing resource.
The company has also used induced polarisation, or IP, surveying to identify chargeability anomalies along strike from Nanadie. According to an ASX release, northern and southern responses were identified in areas that remain sparsely drilled. The northern anomaly extends from the deposit toward areas of historical drilling, while the southern response may indicate a deeper continuation of the mineralised system.
Those geophysical targets do not constitute mineralisation until tested by drilling. They do, however, provide a way to prioritise follow-up holes beneath shallow cover and along geological trends that may not be visible at surface.
The new 148-metre intercept is therefore important not only as an isolated assay result but also as part of a broader exploration program aimed at testing the margins and depth extensions of Nanadie.
Sparse drilling grids are used to test whether mineralisation continues beyond the known resource envelope.
What investors and operators will watch next
The next stage of work will determine whether the new mineralisation can be incorporated into a larger and more confident resource model. Key information will include additional step-out holes, drilling along strike, results from deeper holes and the continuity of grades between sections.
Metallurgical test work will also be important. Nanadie’s mineralisation is described as disseminated and veinlet-style sulphide mineralisation, but recoveries, concentrate specifications and any deleterious elements must be confirmed through representative testing.
The company’s published project information indicates that the Nanadie tenements include a granted mining lease, which may simplify some aspects of future exploration and development planning. That tenure position does not remove the need for environmental approvals, mining studies, metallurgical work, economic analysis and other regulatory requirements.
For now, the 148-metre intercept strengthens the geological case for continuing exploration at Nanadie. It suggests the current resource boundary may not capture the full extent of the copper-gold system, while leaving open the more consequential questions around scale, continuity, confidence and economics.
Fresh mafic rock and sulphide veining are central to Nanadie’s copper-gold geological model.
Bottom line
Solstice’s 148 metres at 0.77% copper and 0.20 g/t gold from NANRCD018 is a strong step-out exploration result outside the current Nanadie resource boundary.
It supports the interpretation of a larger mineralised system and may provide a platform for further resource-extension drilling. But the result remains an exploration intercept, not an economic resource. Its ultimate value will depend on whether follow-up drilling confirms continuity, whether the additional mineralisation can be estimated with appropriate confidence, and whether future metallurgical and mining studies support a viable development case.
Sources: Australian Mining’s report on the Nanadie intercept; Solstice Minerals’ Nanadie project information; ASX release on Nanadie IP targets. Further mining market and exploration coverage is available through Skillings’ Minerals & Metals section.