The 930km² Earaheedy Basin project encompasses terrane prospective for base and precious metals in the Earaheedy and Yerrida basins base metals provinces. The project comprises the Withnell, Terra Rossa and Tableland sub-projects. The Withnell licence is adjacent to the evolving Chinook-Magazine zinc-lead project of Rumble Resources Ltd (ASX: RTR) and north of the Strickland Metals Limited (ASX: STK) Iroquois prospect. The Terra Rossa licences are east of the Thaduna copper deposit (view project map).
The project’s exploration licences have been grouped into the “Terra Rossa” and the “Withnell” sub-projects, which are situated at the western end of the Earaheedy basin, between 40km and 100km east of the De Grussa copper mine and ~120km north of Wiluna; and the “Tableland” sub-project, located in the southeast margin of the basin.
The applications are consistent with Castle’s strategy of positioning itself at low-cost in regions prospective for base and precious metals and which have generally not received much recent attention or the benefit of the latest available exploration tools.
The Withnell project area (granted licence) is immediately north of and, in part, appears to be along strike from the recent Chinook – Magazine zinc-lead discovery (Refer Rumble Resources Limited ASX:RTR releases 8 April 2021 and 19 April 2021) (see project map). An initial appraisal of historical reports and 1:100,000 scale GSWA mapping covering the Withnell licence area indicates that the west extremity and southern portion of the licence most likely encompass the Frere Iron Formation and its unconformable contact with the underlying, prospective Sweetwaters Well member of the Yelma Formation. Importantly, much of the historical exploration in the region occurred in the 1990s with a number of prospects delineated within the Sweetwater Well and overlying Frere Formation. The Withnell application was made on the basis that one such prospect, the Sioux prospect, appears to occur within the Withnell licence area. The exact location and nature of the Sioux prospect has yet to be verified in the field.
The Terra Rossa licences are grouped immediately to the east of the dormant Thaduna copper deposit. They extend north-south for some 40km and host at least six base metal prospects appearing on the GSWA MINEDEX database. Terra Rossa project encompasses a contiguous area overlapping the rocks of the Paleoproterozoic Earaheedy and Yerrida Basins. These areas have undergone several generations of regional-style exploration consisting of soil sampling, RAB and RC drilling. Historical targeting has been directed towards structurally controlled base metal mineralisation associated with regional structural development within both Basins and towards shear-hosted gold mineralisation within the underlying Archean basement. The Yerrida Basin rocks also present an opportunity to target copper and lead-zinc mineralisation given the relatively close proximity to the west of the Thaduna and Green Dragon deposits. These deposits are located within the Thaduna Formation. Whilst this does not appear to cross into the Castle tenure, the Juderina Formation, which occurs in the western part of the licence, does host several copper-lead-zinc occurrences. These include on Castle’s tenure the McDonald’s Well and Little Well prospects.
The largely unexplored Tableland applications encompass Yelma and Frere Formation stratigraphic units and their associated unconformity which has been shown elsewhere in the basin to be prospective for both Mississippi Valley and SEDEX style base and precious metals mineralisation. Importantly, GSWA regional aeromagnetic data indicates a series of north-south and subsidiary northwest trending structures traversing the Tableland areas. These structures appear to be deep-seated and traceable through both the Archean and Paleoproterozoic terranes and may have created a viable framework for the migration of mineralised brines and hydrothermal fluids during early basin formation.
Castle has completed collation and critical review of publicly available historical data and is also evaluating work being undertaken by other companies now active in the region as a prelude to determining the prospectivity of its licence areas.
Based on this detailed review of historical work and the reprocessing and interpretation of available open file airborne EM and magnetic data confirmed that several areas at Terra Rossa and in particular in the vicinity of the McDonald Well base metals occurrence present high priority targets analogous to those of Rumble’s Chinook-Magazine discoveries as well as Castle’s own Sioux prospect on its Withnell licence to the east.
The high amount of transported and in-situ cover over the general tenement area has meant that historical exploration has generally been sporadic and results disappointing with only minor amounts of anomalism encountered during various campaigns. To overcome this impediment, Castle designed and undertook at two priority areas, McDonald Well and Yelma East, soil sampling utilising the fine fraction and CSIRO developed Ultra Fine assay technique. This can be effective in generating gold and base metal anomalies where there is large amount of overburden. As at 28/9/22 results are awaited.
|Project||Licence||Blocks||Area (km²)||Mineral Field||Status||NTLAEA¹|
|Terra Rossa||EL52/3927||70||218||Peak Hill||Granted||Negotiating|
|Terra Rossa East||EL52/3930||34||106||Peak Hill||Granted||Negotiating|
|Terra Rossa South||EL52/3931||39||121||Peak Hill||Granted||Negotiating|
|Ned’s Creek||ELA52/4165||10||31||Peak Hill||Pending||TBA|
|¹ NTLAEA: Native Title Land Access and Mineral Exploration Agreement|