Auriferous lode of Hira-Buddini gold mine,Hutti-Maski schist belt,Dharwar craton: Mineralogy,alteration, types and mechanism of vein emplacement |
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| Authors: | Ajit Kumar Sahoo R Krishnamurthi Prabhakar Sangurmath |
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| Institution: | 1.Department of Earth Sciences,Indian Institute of Technology,Roorkee,India;2.Hutti Gold Mines Company Limited,Hutti,India |
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| Abstract: | The auriferous lode in the Hira-Buddini deposit is confined to the sheared contact of amphibolite and felsic metavolcanic rock. Gold mineralization in the deposit is associated with sub-horizontal, sub–vertical, irregular and with few conjugate veins. These veins were emplaced during deformation in a ductile-brittle regime as inferred from the megascopic features and microstructures of the vein minerals. Fluid pressure was higher than the sum of the minimum principal stress and lithostatic load as well as the tensile strength of the shear zone. Crack-seal process appears to be the mechanism of vein formation. The microstructures of the vein minerals indicate a temperature of ~500ºC during the vein emplacement. In the auriferous lode, amphibolite and felsic metavolcanic rock have been subjected to intense alteration by the ore fluid with development of biotite-chlorite-tourmaline-calcite and muscovite (sericite)-chlorite-calcite-feldspar-biotite assemblages, respectively. Both the altered rocks contain significant amount of pyrite and chalcopyrite with native grains of gold and silver. Post-dating the fluid activity associated with gold mineralization, there is another stage of fluid activity manifested by the calcite veins and micro-veinlets. |
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