Coolyia Project, Pilbara, Western Australia

  • 80% interest in two Exploration Licence at Coolyia Creek, 40km South West of Marble Bar
  • Prospective for Conglomerate Placer Gold Mineralisation
  • Conglomerates on unconformity surface mapped
  • Fine visible gold identified in bulk samples draining unconformity surface and conglomerates

Castle Minerals has an 80% interest in two adjacent exploration licences encompassing the prospective unconformity surface and basal conglomerate horizon of Mt. Roe Basalt.

The project comprises three graticule blocks (12.8km²) at Coolyia Creek, 40km southwest of and easily accessed from Marble Bar in the East Pilbara region of Western Australia (figure 1).

Generally, this area and its surrounds are known to amateur fossickers for gold but until recently no geological context has been applied to gold occurrences in the area.

The vendors of EL45/4965 have discovered an auriferous quartz reef within old Archean basalts where they have recovered a number of gold nuggets off the reef and surrounding areas. In addition, recent scraping and gold detecting on EL45/4975 was observed which predates the tenement application.

Castle geologists have completed detailed geological mapping and stream sediment sampling on the project focussing on the base of Mt Roe Basalt unconformity and overlying conglomerate units with positive results (refer ASX announcement “Visible Gold in Bulk Stream Sediment Concentrates” released 5th June 2018). The work completed to date has mapped two conglomerate units overly the unconformity surface (figure 1). In addition, 15 bulk (15 kg) stream sediment samples were collected from streams draining the unconformity surface and conglomerate units. Five of the sample sites recovered visible gold from a super concentrator purchased by the company to process field samples on site. Sub samples from the bulk samples were submitted to the laboratory and returned up to 144 ppb Au.

Future Work

The company's initial object is to identify insitu free gold within conglomerates similar to the Purdey’s discovery by Novo. Work completed to date has been encouraging, with the recovery of visible gold in streams draining the unconformity and conglomerate units. Further infill sampling over anomalous areas is required to define target areas for a large (>1 tonne) bulk sampling program.

There is considerable geological conjecture as to the origin of paleo-placer gold in the Pilbara region. It is known to occur in the Hardey conglomerate and/or a stratigraphically lower conglomerate horizon occurring at the base of the Mt Roe basalt itself. These occurrences are distinct from gold associated with other styles of mineralisation such as epithermal quartz vein hosted gold.


Castle has an 80% interest in the tenements. The vendors retain a 20% free carried interest to a decision to mine and will receive a 1% net smelter royalty on all mineral production for the tenements.