Highly pure placer gold formation in the Nilambur Valley,Wynad Gold Field,southern India |
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| Authors: | M Santosh R Philip M K Jacob P K Omana |
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| Institution: | (1) Laboratoire de Geochimie des Isotopes Stables, Tour 54/64, Université de Paris 7, 2 Place Jussieu, 05 Paris, Cedex, France;(2) Centre for Earth Science Studies, 695 031 Trivandrum;(3) Department of Geology, University of Kerala, India;(4) Department of Geology, S.N. College, Varkala, Trivandrum, India |
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| Abstract: | Placer gold grains in the Nilambur Valley of Wynad Gold Field in southern India are characterized by very high purity levels (985–1000). Their Ag-depleted core compositions, enhanced grain size and microscale growth patterns correlate with gold grains associated with laterite profiles in the weathering fronts. From the morphological and chemical evolution of gold grains associated with primary, supergene and secondary deposits in this region, we identified a two-stage process for the evolution of the highly pure placers, which shows that gold in the primary veins was mobilized, chemically purified, and reconcentrated in the laterite profiles, effecting enhanced purity and grain growth before transfer to the fluvial system. Further refinement was achieved during fluvial transport, generating natural concentrations of pure gold in the placers. |
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