CRC LEME
Open File Report 41
ABSTRACT
Hydrogeochemistry of the Panglo Gold Deposit
Gray, D.J.
A hydrogeochemical survey of the Panglo Gold Deposit was conducted
by sampling groundwaters in open drill holes, and from drainage
holes in the Trial Pit. Waters were sampled from the three main
geological environments of the area, namely shales in the south-east
of the study area, mafic rocks, and ultramafic rocks.
The chemical characteristics of the water samples are closely correlated
with the lithology in which the water was sampled. Waters derived
from shales have relatively low concentrations in Au, the pathfinders,
and most of the chalcophile elements analysed, whereas waters derived
from mafic and ultramafic rocks have characteristic multi-element
'signatures'. Waters associated with mafic rocks are strongly enriched
in Mn, Co, and Zn, and weakly enriched in Cu and Ni, whereas waters
associated with ultramafic rocks are enriched in Ni, Cr, Bi, Sc
and Ag. Using these data, water samples could be distinguished into
geological groupings by using chemical compositions alone.
Chemical data also suggest major variations in the degree of weathering
and leaching within the sample area. Waters in the northern part
of the study area are highly acidic and oxidising, and have anomalously
high concentrations of Au, Br, Fe, Mn, Co, Zn, Cu and Ni. Dissolution
of Au is primarily controlled by the redox status of the solution.
Elevated Eh levels are caused by Mn oxidation, permitting the oxidative
dissolution of native Au and its mobilisation by either the chloride
or the iodide complexes. Dissolution of Au as the iodide complex
occurs as a consequence of the relatively high concentrations of
I at this site. Such a Au mobilisation mechanism has not, in the
author's experience, been previously documented for groundwaters.
The concentration of dissolved Au is high, and would represent a
reasonable exploration method at this site.
Last updated: Thursday, January 06, 2000 08:32 AM
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