Search CRC LEME :

powered by FreeFind

Publication Policy

Open File Report Series

OFRS Index


Regolith Maps

Annual Reports

Articles & Papers


Minerals Briefs

"Focus on Salt"

Other LEME Reports

Order Form

Open File Report 96

Selective extraction techniques for the recognition of buried mineralization, Curara Well, Western Australia

Gray, D.J.

The Curara site was selected for initial investigations of the utility of partial/selective extraction for mineral exploration in the Yilgarn. There are up to 20 m of barren transported overburden over laterite, which is enriched in Au above primary mineralization. It was considered that MMI (mobile metal ion) extractions were successful in locating the buried mineralization. This was tested, using one soil profile in the middle of the mineralized zone, two traverses across the region of Au-rich laterite and one traverse in a background area, which were treated using standard selective extraction techniques. The first extraction, acetate, which measures pH 5 soluble metals, shows no direct correlations with underlying Au-rich laterite, except for Mn, which appears to be moderately enriched directly above mineralization. The second extraction, hydroxylamine, which extracts Mn oxides and amorphous Fe oxides, gives higher levels of Fe, Mn, Cu, Zn and Pb overlying mineralization. The best signal to noise contrast was obtained for Mn, and is clearly caused by significant concentrations of separate phase Mn oxides above the Au-rich laterite. Analysis of the data suggests that the higher concentrations of extractable base metals are primarily due to association of these metals with Mn oxides. Furthermore, examination of the MMI results suggested that those MMI extractable metals showing high contents over mineralization (e.g., Cu and Cd) were also associated with Mn oxides.

The enrichment in Mn over mineralization is greater than 800 ppm, which cannot be characterized as a subtle extraction anomaly. Despite some evidence for moderate Mn enrichment in groundwaters contacting mineralized areas, it is considered that there is unlikely to be a direct link between the surface Mn anomaly and the Au-rich laterite ten or more metres below. Instead, it is likely that surface phenomena, such as an observed drainage system through the anomalous area, is the cause of this effect. This suggests that the MMI and CSIRO extraction results showing a correlation of greater extractable metals with buried Au-rich laterite at Curara is coincidental.

It is considered that partial extractions (such as MMI or enzyme leach) can only be understood and interpreted correctly if conducted in conjunction with determinations of the levels of critical soil phases such as Mn oxides, amorphous Fe oxides and/or any other materials expected to adsorb or otherwise accumulate dissolved ions at the site under investigation.

Last updated: Friday, July 21, 2000 04:24 PM


Cooperative Research Centres Australia

About Us | News & Events | Research
Publications | Education | Staff Only | Links

Contact Us | Disclaimer | Sitemap
© CRC LEME 2004

CRC LEME is established and supported under the Australian Government's Cooperative Research Centres Program. The CRC Program is an Australian Government initiative which brings together research groups with common interests.

CRC LEME Core Parties