CRC LEME
Open File Report 8
ABSTRACT
Report on laterite geochemistry in the CSIRO-AGE Database for
the Southern Murchison Region (Yalgoo, Kirkalocka, Perenjori, Ninghan
Sheets)
Grunsky, E.C., Innes, J., Smith, R.E. and Perdrix, J.L.
A multi-element geochemical study, largely based upon laterite
sampling, covering parts of the main greenstone belts of the Perenjori,
Nyngan, Yalgoo, and Kirkalocka 1:250 000 map sheets has outlined
the following geochemical features:
- district-scale (30 to 50 km in length) patterns in the distribution
of Cu + Zn + Ni + Co + Cr; V + Sn;, and Zr + Nb; each pattern
appearing to relate to dominant characteristics of varying bedrock
associations;
- an As + Sb association in the Yalgoo-Singleton Greenstone Belt,
most prominent in a central regional north-south trend (referred
to as a chalcophile corridor, Smith, 1987) passing through Golden
Grove and extending south to Mt Gibson;
- isolated anomalies on the 2 to 5 km scale showing associations
of Bi + Mo + W+ Ge + Sn; and,
- several anomalies at the 1 km scale that require follow-up sampling
in exploration in order to assess their continuity and significance.
The study also provides knowledge of the element abundance levels
and variation of laterite geochemistry that complements information
arising from orientation studies about mineral deposits.
Sporadic Au anomalies also occur. However, the general sample spacing
of 3 km with fill-in sampling at 1 km is too wide for reliable interpretation
of Au patterns in laterites. Laterite geochemistry at these low
sample densities generally requires the use of intermediate zonal
targets such as anomalous chalcophile envelopes which can occur
about individual deposits. The sampling arose as part of a combined
research programme at CSIRO and an experimental exploration programme
(the AGE Joint Venture Programme) during the period 1983 to 1986.
In the region covered by the present report a total of 721 samples
were analyzed for 31 elements. Summary statistics, histograms, and
maps of the percentile classes, are presented for selected elements
in laterites and some very iron-rich materials from partly eroded
profiles which have been referred to as ferricretes. A principal
components analysis was also carried out with the resulting component
scores plotted up for the first five components. The results of
the analysis confirm the presence of some broad regional geochemical
trends that are related to bedrock lithologies and regional alteration
processes.
Last updated: Tuesday, January 04, 2000 10:20 AM
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