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Regolith Geoscience

 

Exploring through cover in the Central Gawler

Project Leader : J Keeling

Start date and duration: 01/07/03 30/06/08

Participants : Primary Industries and Resources SA, CSIRO Exploration and Mining, Adelaide University, Geoscience Australia


Brief project description :

An arcuate belt of Proterozoic rocks in the central Gawler Craton has been recognised as a potential new gold province of regional significance. Deposits at Tarcoola, Boomerang, Glenloth and Earea Dam, together with new gold prospects at Tunkillia, Nuckulla Hill, Barns, Baggy Green and Weednanna outline a >500 km long arcuate belt of similar mineralisation and alteration styles. That such a regional gold system has gone largely unrecognised is due to the presence of extensive cover sediments, a gold-depleted regolith and the lack of an effective exploratory tool, until the widespread use of calcrete geochemistry in the mid-1990s.

Some companies have experienced significant success with Au-in-calcrete sampling while others have been frustrated by the difficulty in discriminating between anomalies closely associated with bedrock mineralisation and spurious anomalies associated with significant thicknesses of transported regolith. The project addresses the need for additional data on landscape history, metal mobilisation through cover and development of supplementary targeting techniques to plan effective drilling programs, in particular to test calcrete anomalies.

Since mid-2005, the central Gawler Craton has also been targeted by exploration companies for sedimentary uranium with a consequent high demand for project data on the distribution and architecture of palaeodrainage sediments in the area. An improved map showing palaeochannel sediment distribution on the Gawler Craton is now planned for 06-07 in conjunction with anticipated new data coming from company exploration drilling for uranium.

Zircon dates from the Eucla Margins project indicate that the source of heavy minerals at Jacinth deposit is dominantly from the Musgrave Ranges . It is proposed that during 2006-08, a GIS of available data including palaeodrainage and sediment cover in the area south of the Musgrave Block to the margin of the Eucla Basin will be compiled. Heavy mineral suites from Tertiary and Permian sediments will be analysed from selected drill hole samples held in PIRSA's Core Storage Facility to track heavy mineral dispersion. These data will aid models of HM distribution in marginal marine sediments of the Eucla Basin .

Deliverables (outputs) and expected impacts of research (outcomes):

Outputs

•  GIS including data on: regolith thickness - regolith type - palaeo-drainage - geochemistry

•  Distribution and description of sedimentary cover in the Central Gawler Craton

•  Dating and evolution of the palaeodrainage system

•  Dating dune and sand spread cover

•  Understanding metal mobilisation through sediment and dune cover

•  Prospect scale preliminary models of

•  landscape evolution (includes: regolith stratigraphy dating transported cover and reference site description and maps)

•  weathering of the primary mineral system

•  physical dispersion processes

•  hydro-geochemical dispersion processes

•  role of vegetation in cycling of Au

Outcomes

Outcomes anticipated include uptake of regional data products and use of identified regolith vectors to mineralisation, leading to increased and more efficient mineral exploration in the area with improved exploration success.

 

 

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