• S J CHAVAN

      Articles written in Journal of Earth System Science

    • Hydrothermal activity in the basement granite associated with the unconformity-related uranium deposit in Chitrial area, Cuddapah Basin, India

      JUGINA THOMAS M S PANDIAN TRESA THOMAS P K THOMAS S J CHAVAN P V RAMESH BABU H S RAJARAMAN

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      Uranium mineralization occurs adjacent to the unconformity between Paleoproterozoic granite and Meso- to Neoproterozoic cover sediments in Chitrial prospect of Cuddapah Basin in Indian shield. Hydrothermal activity in the granite is evident by the presence of hydrothermal veins and associated wallrock alteration in the unconformity zone (0–5 m below unconformity), shallow zone (5–100 m), and deep zone (100–120 m). Hydrothermal alteration of granite has produced chlorite in all depth, epidote in the deep zone, muscovite commonly in the shallow zone and illite predominantly in the unconformity zone. Pitchblende and coffinite are associated with sulphides and carbonaceous matter filling micro fractures and occurring along grain boundaries in the granite. Fluid inclusion study of quartz from hydrothermal veins reveals the presence of primary aqueous inclusions (biphase, monophase, polyphase) with a wide range of salinity from 0.2 to >23.2 wt.% (low–high). The fluid composition indicates that MgCl$_{2}$ is present in all depth zones, CaCl$_{2}$ in the deep zone and KCl–NaCl in the unconformity zone. T$_{h}$ of aqueous biphase inclusions is in the range of 275.0–78.9$^{\circ}$C. Available evidence suggests convective circulation of basinal brine between cover sediments and basement granite during which uranium was mobilized from granite and precipitated in the unconformity zone.

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