Depletion zones of ore elements: A significant tool in mineral exploration

Category Mineral processing
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Goldberg, Issai۱; Abramson, Grigory۱; Los, Vladimir۲; Nazarov, Valeri۳
Holding Date 03 September 2008

Existing geochemical methods of exploration of any scale are designed to identify anomalous areas of high metal concentration. These criteria, including the magnitude of values and the size of anomalous areas, are the principal ones employed in assessing the potential of areas under investigation. At the same time, these criteria do not always yield unambiguous results – it is not unusual for metal anomalies significant both in dimension and intensity to subsequently prove barren.
There are several available methods of enhancing the effectiveness of geochemical exploration. They include such criteria as geochemical zonality of ore elements, geological position areas etc. However, even when all these established methods are employed, the problem of assessment of the potential of an area remains.
Enhancement of predictability of potential can be achieved by the addition of another criterion which until now has been little used or ignored. It is known that zones of enrichment in ore-bearing regions are accompanied by areas of reduced concentrations of these elements (lower than background levels). In some cases these appear to be spatially linked to each other and may be seen as a single geochemical system. Geochemical systems are fractal and retain a similar pattern at all scales. Zones of depletion are common for all basic ore elements, including metals with such low Clarke values as Sn, Au, Pt and others.
The dimensions of depletion zones of ore forming elements exceed the size of enrichment zones by an order of magnitude. A clear linear correlation has been shown to exist between the size of depletion zones in geochemical systems and reserves of metal. A study of this correlation has been conducted on deposits of differing composition, including tin deposits (Russian Far East), gold deposits (Bendigo area in central Victoria, Australia) and VMs Deposits (Rudny Altay, Kazakhstan).
This correlation could be a key criterion for assessing a target region, since the size of a geochemical system’s depletion zone provides both an indication of the potential of a positive anomaly and also enables a judgment to be made about the scale of ore metal accumulation.

 

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