Changes in tourmaline composition during magmatic and hydrothermal processes leading to tin-ore deposition: The Cornubian Batholith,SW England |
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| Institution: | 1. GFZ German Research Centre for Geosciences, 14473 Potsdam, Germany;2. Fachgebiet Mineralogie-Petrologie, Technische Universität Berlin, 13355 Berlin, Germany;3. Faculty of Geosciences & MARUM - Center for Marine Environmental Sciences, University of Bremen, 28359 Bremen, Germany;4. Department of Earth and Planetary Sciences, McGill University, Montreal, Canada;1. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, PR China;2. Faculty of Earth Resources and Collaborative Innovation Center for Exploration of Strategic Mineral Resources, China University of Geosciences, Wuhan 430074, PR China;3. State Key Laboratory for Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210093, PR China;4. School of Ocean and Earth Science, University of Southampton, Southampton SO14 3ZH, UK;1. Key Laboratory of Orogenic Belt and Crustal Evolution, School of Earth and Space Sciences, Peking University, Beijing 100871, China;2. ARC Centre of Excellence in Ore Deposits (CODES), University of Tasmania, Private Bag 79, Hobart 7001, Australia;3. School of Resources and Environmental Engineering, Hefei University of Technology, Hefei 230009, China;4. Department of Sciences and Technology, The Inner Mongolia Autonomous Region, Hohhot 010010, China;1. CAS Key Laboratory of Crust-Mantle Materials and Environments, School of Earth and Space Sciences, University of Science and Technology of Chinas, Hefei 230026, China;2. CAS Center for Excellence in Comparative Planetology, Hefei 230026, China;3. Wuhan Centre of China Geological Survey, Wuhan 430205, China;4. Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration, College of Earth Sciences, Guilin University of Technology, Guilin 541004, China |
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| Abstract: | To investigate the potential of tourmaline as a geochemical monitor, a comprehensive dataset on major, minor and trace element concentrations as well as Fe3+/ΣFe ratios of tourmaline is presented. The dataset includes samples from five plutonic complexes related to diverse magmatic to hydrothermal stages of the Cornubian Batholith (SW England). Tourmaline composition found in barren and cassiterite-bearing samples include all three primary tourmaline groups and tourmaline species with the general endmembers schorl, dravite, elbaite, uvite, feruvite, foitite and Mg-foitite.Based on textures and compositions, it is possible to distinguish not only between late-magmatic and hydrothermal tourmaline, but also between several formation stages. Hence, tourmaline monitors late-magmatic processes and the partitioning of elements during exsolution of an aqueous phase. For example, in hydrothermal tourmaline Sn is strongly enriched, while Ti, Cr, V and Sc are depleted compared to late-magmatic tourmaline of the same sample. Several tourmaline generations that precipitated from magmatic fluids can be distinguished with differing major and minor elements and REE patterns depending on the composition of the melt from which they were expelled from. Strongly zoned tourmaline allows for unraveling the hydrothermal history of a distinct location including ore precipitation. The precipitation of SnO2 in the study area was probably caused by mixing between acidic, reduced, Sn-bearing magmatic fluids and oxidized meteoric fluids, which is in agreement with London and Manning (1995) and Williamson et al. (2000). Hence, the ability of tourmaline composition to monitor changes in Sn concentration and redox conditions in hydrothermal fluids has potential as an exploration tool. |
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| Keywords: | Tin Greisen Mössbauer spectroscopy Fluid Trace elements Redox |
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