Castle Minerals Limited (ASX: CDT) has confirmed that previous explorers encountered several zones of base metal anomalism on the recently applied for Withnell and Terra Rossa exploration licences in the Earaheedy Basin region of Western Australia through an extensive review of historical open-file reports.
Castle’s five licence applications extend for a combined 863 sq. km and have been explored over the past 40 years by a series of companies searching for various styles and combinations of base metals, gold and diamonds.
These companies have included CRA Exploration Pty Ltd (CRAE), Esso Minerals Ltd, Western Mining Corporation Limited, Plutonic Gold Mines Ltd, RGC Exploration Pty Ltd, Placer Dome Limited, Kalamazoo Resources Ltd, Lodestar Minerals Limited and Pacmag Metals Ltd.
Castle Managing Director, Stephen Stone, said exploration on Castle’s licences has included mapping, lag sampling, pisolite sampling, rock chip sampling, BLEG sampling, auger sampling, aeromagnetics, VTEM, RAB, aircore, RC and core drilling.
This work was of a good quality for its time but was not especially directed towards the discovery of the broad SEDEX style of mineralisation as is being interpreted at the Rumble Resources Ltd (“Rumble”) held Chinook-Magazine prospects. Nevertheless, the work provides an invaluable platform from which to advance exploration at Earaheedy.
Historical reports have highlighted the prospectivity of the substantial foothold that Castle has secured in the emerging Earaheedy Basin base metals mineral province,” Mr Stone said.
“Diamond drilling in 1994 by RGC Exploration Pty Ltd, on what is now Castle’s Withnell application area, confirmed anomalous zinc-lead mineralisation at the Sioux prospect. This occurs at a similar stratigraphic level as the rock units that host immediately along strike the Chinook and Magazine prospects of Rumble Resources Ltd.”
“Historical exploration on the Terra Rossa group of licences identified at least six areas of base metal anomalism. Some of this anomalism also occurs at the same stratigraphic level as at the Chinook, Magazine and Sioux prospects whilst some interestingly occurs lower in the stratigraphic sequence.”
Castle’s Withnell application area hosts the Sioux prospect, one of several identified in 1997 by a Renison and Carnegie Minerals NL joint venture. This was the same joint venture that identified the Chinook and Magazine prospects now being explored by Rumble Resources.
RC and diamond drilling by Renison intersected low-level zinc and lead anomalism on the Withnell licence including at the Sioux prospect. It also recorded a lithological sequence very similar to that at the Chinook and Magazine zinc-lead discoveries to the west, with the Sioux anomalism appearing to be hosted in a similar lithological zone.
Historical reports, 1:100,000 scale GSWA mapping covering the Withnell application and projections of lithologies to surface indicate that the Withnell licence could host approximately 3.5km strike of the prospective Lower Frere Formation – Upper Yelma target lithological zones.
Confirming the exact collar position of the Renison drill holes will be Castle’s priority activity in a field verification and reconnaissance exploration program which will commence shortly.
Castle also notes that the prospective lithological unit dips very gently to the northeast. The projected depth at which the mineralised unit on the Rumble licence appears on that portion of Castle’s Withnell licence, which also abuts the northern boundary of the Rumble licence, is undetermined and will need to be confirmed by drilling.
Rumble (ASX release 2 June 2021) also refers to the presence of a ‘swarm’ of northwest trending structures that may have acted as conduits for mineralising fluids to find their way into the now mineralised lithology. They may have also favourably influenced the distribution of mineralisation, with the implication being that higher grade zones will be closer to the fractures.
Castle has yet to locate any high-definition aeromagnetic data that could aid in the structural interpretation of the Withnell license area and in particular whether or not these structures exist on its licence. Given the broader deformation history of the Earaheedy Basin, the likelihood is that the structural fabric will be similar. Confirming this will be another focus for Castle’s geologists.
The four contiguous Terra Rossa applications 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. All have been variously explored over the past 40 years by a variety of companies that have filed numerous reports on their activities.
The exploration carried out on all the license areas has been on a regional reconnaissance basis with some limited follow-up work consisting of sporadic RAB, aircore and RC drilling. Programs generally comprised various types of regolith sampling due to limited outcrop. The historical exploration confirmed that base metal mineralisation is found within all of the Terra Rossa licences and that the region is fertile for discoveries.
Most soil sampling and drilling on the Terra Rossa package took place on ELA52/3927 and in particular, in and around the McDonald Well South copper-zinc target where one of four RC holes to test an EM conductor returned low-level copper and gold.
The Elmos base metal anomaly was identified by mapping and lag sampling conducted by CRAE in 1994. RAB drilling intersected low-level base metal anomalism with the actual stratigraphy hosting this then being the subject of some technical debate.
The 800m x 300m Terra Rossa base metal anomaly was identified by CRAE at the same time as the Elmos and the nearby Brimstone anomalies were identified. Terra Rossa was tested with a single RAB hole which returned anomalous zinc and copper.