International Geologiical Congress - Oslo 2008


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MRD-12 Fluvial palaeo-systems: Evolution and mineral deposits


Study and development of CHIM geoelectrochemical method for exploration of concealed mineralisation in China


Xianrong Luo, Guilin Insititute of Technology (China)
Baohong Hou, CRC LEME, Minerals and Energy (Australia)
Nanshi Zeng, Guilin Insititute of Technology (China)


The CHIM (CHastichnoe Izvlechennye Metallov, commercially known in the former USSR) geoelectrochemical technique is applied to explore for concealed ore bodies by exciting and extracting metallic ions in the zones nearby ore bodies under an applied electric field. By comparing with geoelectrochemical extraction anomalies of known concealed ore bodies, some new ore bodies were discovered in China, Ukraine, Russia and Canada.

Based on both experimental works and field tests for over ten years, the mechanism and effectiveness of the geoelectrochemical extraction technique, in exploration for concealed mineralisation through regolith cover in China, are briefly reviewed and demonstrated. Two main aspects of the method are discussed: a) how metallic ions released from ore body by electrochemical dissolution, and b) how these ions migrated to the collector deposited as elements by electrochemical extraction during the processes of electric field.

Both laboratory and field studies with this geoelectrochemical extraction method show that metallic ions around an ore body are mainly derived from electrochemical dissolution and move to the collector under the action of electric field extraction. The method of diffuse extraction of metal ions under the action of electrical currents uses specialised synthetic sorbent collectors, and successfully combines hydrogeochemical dispersion and sorption technology for mineral prospecting. It is possible to fix and accumulate the mobile form of many target elements using purpose designed ion-exchange resins, and other sorbents, for specific cations or anions.

The extraction and analysis of elements in the form of mobile ions that can migrate over large distances have revealed and traced concealed and overlapped ore bodies. A number of case studies have demonstrated that the geoelectrochemical extraction technique can detect concealed metallic mineralisation (eg., copper, lead, zinc, tin, gold, silver, arsenic and antimony) at a depth of more than (up to?) 500m in various landscapes and climatic environments.
The geoelectrochemical extraction technique is a useful and effective approach for mineral exploration, especially in arid to semi-arid regions with transported regolith, where conventional geochemical methods are confronted with serious limitations. It is also a useful and effective means for evaluating anomalies defined by conventional geophysical or geochemical methods because this technique measures directly the ions released from the target anomaly.
In areas of transported overburden or deep weathering, this technique is more effective than other conventional geophysical and geochemical methodologies; at least it can enhance any weak anomalies. The prospecting depth may be significantly greater than conventional geochemical methods because the technique activates, collects and concentrates the more mobile ions.


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