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Characterisation of gold from Fiji

By Jon Naden and P.J. Henney

Abstract

This is a study of the variation in chemistry and inclusion mineralogy of\ud bedrock and placer gold from Fiji. It forms part of a large project,\ud undertaking gold characterisation from a wide range of geological\ud environments in Ecuador, Zimbabwe, Malaysia and Fiji. The work was\ud carried out under the Overseas Development AdministratiodBritish\ud Geological Survey Technology Development and Research programme\ud (Project R5549) as part of the British Government’s provision of technical\ud assistance to developing countries. For the Fijian component of the\ud project, samples were collected from river gravels, primary ore, and table\ud concentrates.\ud In total thirty-five samples from five localities were examined. Data\ud collected from these samples are represented by over 100 point analyses of\ud gold, identification of associated minerals, and microgeochemical maps of\ud gold-mineral intergrowths.\ud A framework for identifying possible sources of alluvial gold is given. This\ud was achieved by characterising bedrock gold mineralisation from a variety\ud of epithermal and porphyry environments. The environments studied\ud included alkali (the Emperor Gold Mine), high-sulphidation (the Mount\ud Kasi prospect) and telescoped (the Tuvatu prospect) systems.\ud A study of placer gold from the Waimanu alluvial deposit, the only alluvial\ud gold deposit in Fiji, showed two distinct sources of gold: one, a low-silver\ud type, associated with Cu-Fe sulphides, can be related to the nearby\ud Namosi porphyry copper deposit. The other source, a high-silver type with\ud abundant tellurides, indicates an alkali epithermal association, suggesting\ud a source similar in style to the mineralisation observed at Emperor Gold\ud Mine.\ud The identification of two bedrock sources for the Waimanu alluvials\ud clearly shows that there must be a, yet unknown, alkali epithermal\ud (Emperor) source within the Waimanu catchment. This demonstrates the\ud power of alluvial gold characterisation and its role in gold exploration.\ud An important implication of these results is that future exploration within\ud the area should be focussed on locating this “Emperor type” source

Publisher: British Geological Survey
Year: 1995
OAI identifier: oai:nora.nerc.ac.uk:9671

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