Queensland Geological Record 2009/02
A summary of company exploration results for minerals and petroleum
in the Mount Whelan 1:250 000 (SF54-13) Sheet area, central west Queensland
1:250 000 (SF54-13) Sheet area for mineral commodities and petroleum
other than water and coal. Exploration for minerals was conducted
under Exploration Permits for Minerals (EPM) and for petroleum under
Authorities to Prospect for Petroleum(ATP).
Mineral exploration was conducted over the southern part of the Georgina
Basin and the central part of the Eromanga Basin. Exploration focused
on the potential for an alluvial diamond deposit and diamonds from
a primary source along the south-eastern margin of the North Australian
Craton. This exploration was basedon the presence of continuous and
deep (>200km) fast seismic velocity data that indicates a thick lithospheric
mantle root beneath the southern Georgina Basin.
The Silurian - Devonian Craven Peak beds on the Toomba Range were
explored for primary diamond deposits due to the presence of detrital
chromites that reflected a lamproite origin. Concurrently, Ordovician
age rocks of the Toko Group were explored using a kimberlitic model
following up scattered occurrences of detrital chromite and picro-ilmenite
grains from around Beattie Creek and Toko Range. No discrete diamond
primary source has been discovered.
Older rocks commonly associated with a Cambrian age basement high
in the Georgina Basin are buried beneath a >300m thick sedimentary
cover of Mesozoic rocks. The western margin of the Toomba Fault Zone
was explored for Carlin-style precious metal replacement deposits
apparently associated with buried rock structures showing magnetic
and gravity trends. Company exploration for minerals intersected gneiss
and granitoid basement rocks of Proterozoic age in drill holes up
to 464m in depth. The drilling indicated an apparent uniform succession
of Middle Cambrian rocks dipping gently to the west into the Toko
Syncline. Traces of pyrite, sphalerite, galena and fluorite were encountered
in dolomitic sections of the Thorntonia Limestone, which is also enriched
in bitumen.
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