Contrasting fluid inclusion characteristics of staniferous and non-staniferous pegmatites of Southeast Bastar,Central India |
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| Institution: | 1. Centro de Pesquisas Professor Manoel Teixeira da Costa (CPMTC), Instituto de Geociências, Universidade Federal de Minas Gerais (UFMG), Av. Antônio Carlos 6.627, 31270-901 Belo Horizonte, MG, Brazil;2. Centro de Desenvolvimento da Tecnologia Nuclear (CDTN), Av. Antônio Carlos 6.627, 31270-901 Belo Horizonte, MG, Brazil;3. Institut für Angewandte Geowissenschaften, Mineralogie und Petrologie, Karlsruher Institut für Technologie (KIT), Adenauerring 20b, Geb. 50.40, 76131 Karlsruhe, Germany;4. Vale Manganês S.A., Rua Duque de Caxias s/n, Morro da Mina, 36400-000 Conselheiro Lafaiete, MG, Brazil;5. Institute of Disposal Research, Technische Universität Clausthal, Adolph-Roemer-Str. 2a, 38678 Clausthal-Zellerfeld, Germany;6. Mineral Resources, Technische Universität Clausthal, Adolph-Roemer-Str. 2a, 38678 Clausthal-Zellerfeld, Germany;1. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing, 100083, China;2. Research Institute of Land Resources, Zhengzhou, 450053, China;3. Chinese Academy of Geological Sciences (CAGS), Beijing, 100037, China;1. Department of Sciences, University of Basilicata, viale dell''Ateneo Lucano 10, 85100 Potenza, Italy;2. National Research Council – Institute of Methodologies for Environmental Analysis, c/da S. Loja, 85050 Tito Scalo, Italy;3. Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Palermo, via Ugo La Malfa 153, 90146 Palermo, Italy;1. Department of Geology and Paleontology, Faculty of Natural Sciences, Comenius University, Ilkovičova 6, SK-842 15 Bratislava, Slovakia;2. Department of Mineralogy and Petrology, Faculty of Natural Sciences, Comenius University, Ilkovičova 6, SK-842 15 Bratislava, Slovakia;3. Earth Science Institute, Slovak Academy of Sciences, Dúbravská cesta 9, SK-845 28 Bratislava, Slovakia;4. Earth Science Institute, Slovak Academy of Sciences, Workplace Banská Bystrica, Ďumbierska 1, SK-974 01 Banská Bystrica, Slovakia |
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| Abstract: | Tin and rare metal-bearing granitic pegmatites in the Bastar–Malkangiri pegmatite belt of Central India are hosted by metabasic and metasedimentary country rocks. Fluid inclusion studies were conducted in spatially associated two-mica granite and the staniferous and non-staniferous pegmatites to characterize the physicochemical environment of mineralization, to distinguish different pegmatites in terms of their fluid characteristics and to envisage a possible genetic link between the pegmatites and spatially associated granite. Three different types of primary inclusions were identified. The type-I, aqueous bi-phase (L+V) inclusions are the most abundant and ubiquitous. Type-II polyphase (L+V+S) inclusions are rare. Type-III, monophase (L) and metastable aqueous inclusions, though less abundant than type-I inclusions, are ubiquitous. The fluid evolution trends indicate that mixing of two different fluids of contrasting salinities, one of high salinity (20–30 wt% NaCl equivalent) and another of low salinity (0–10 wt% NaCl equivalent), was responsible for precipitation of the bulk of the cassiterite. This mixing is the single most important characteristic that distinguishes the staniferous pegmatites from their non-staniferous counterparts. The non-staniferous pegmatites, on the other hand, are typified by the presence either of a high saline or a low saline fluid that evolved through simple cooling. The minimum pressure–temperature of entrapment, estimated from the intersections of the halide liquidus with the corresponding inclusion isochores of type-II inclusions, range between 2.1–2.2 kb and 300–325 °C. The similar P–T range of fluid entrapment of the staniferous and non-staniferous pegmatites indicates that they were possibly emplaced within a similar physical environment. Type-I inclusions from granite recorded only the high salinity fluid, the salinity of which compares well with that of the highly saline fluid component of type-I inclusions in the pegmatites. This is a possible indication of a genetic link between the pegmatites and spatially associated granite. |
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