CRC LEME
Open File Report 71
ABSTRACT
Radioelements in weathered shales and mafic volcanics, Panglo
Gold Deposit, Eastern Goldfields, WA
Scott, K.M. and Dickson, B.L.
The K, eU and eTh contents of 111 samples of shales, mafic volcanics
and dolerites from the Panglo gold deposit have been determined
radiometrically. Shales have consistently higher K, eU and eTh contents
than the mafic volcanics and dolerites. However, within shale profiles
above the Au mineralization, eTh and eU contents are low relative
to equivalent barren profiles. This feature is similar to the behaviour
of Sr in the same shale profiles (Scott, 1989a) and, with the additional
constraints imposed by the geochemistry of Th, an hypothesis to
account for the mineralogical and geochemical features in the shale
is presented. Under the acid sulphate conditions resulting from
the weathering of sulphides, Th (and U) are envisaged as having
migrated from more acid areas to what is now the periphery of the
deposit where they are adsorbed onto and/or incorporated into Fe
oxides. Strontium in hanging wall rocks at the edge of the deposit
is contained largely in Na-rich phyllosilicates which formed during
the interaction of later saline groundwaters with the original mica.
This saline ground water is probably responsible for the formation
of the Ag-free supergene gold deposit at Panglo.
Twenty-seven soil samples from over the deposit have similar concentrations
of K, eU and eTh. Because they show no variations which can be related
to the underlying geology, a major transported component within
the soils is suggested. The eU and eTh contents of pisoliths within
the soils indicate that eU and eTh are specifically related to the
iron oxide components.
Last updated: Thursday, January 06, 2000 11:46 AM
|
