Late Cretaceous magmatism and related metallogeny in the Tengchong area: Evidence from geochronological,isotopic and geochemical data from the Xiaolonghe Sn deposit,western Yunnan,China |
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| Institution: | 1. Chengdu Center, China Geological Survey, Chengdu, 610081, China;2. College of Earth Sciences, Chengdu University of Technology, Sichuan, Chengdu 610059, China;3. State Key Laboratory of Geohazard Prevention and Geoenvironment Protection, Chengdu University of Technology, Chengdu 610059, China;4. School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China;1. State Key Laboratory of Continental Tectonics and Dynamics, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;2. State Key Laboratory for Mineral Deposits Research, Department of Earth Sciences, Nanjing University, Nanjing 210046, China;3. Geological Survey of Yunnan Province, Kunming 650051, China;4. Geologisches Institut, ETH Zurich, 8092 Zurich, Switzerland;1. Beijing SHRIMP Center, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;2. Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia;3. Department of Earth and Environment, Boston University, Boston, MA 02215, USA;4. Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China;1. State Key Laboratory of Geological Processes and Mineral Resources, and School of Earth Science and Resources, China University of Geosciences, Beijing 100083, China;2. CAS Center for Excellence in Tibetan Plateau Earth Sciences, Beijing 100101, China;1. School of Earth Science and Resources, China University of Geosciences, Beijing 100083, China;2. The Beijing SHRIMP Center, Institute of Geology, Chinese Academy of Geological Sciences, Beijing, 102206, China;3. Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China;1. Key Laboratory of Metallogenic Prediction of Nonferrous Metals, Ministry of Education, School of Geosciences and Info-physics, Central South University, Changsha 410083, PR China;2. State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, PR China;3. Solid Earth Studies Laboratory, Department of Geology, University of Regina, Regina, Saskatchewan S4S 0A2, Canada;4. Lunar and Planetary Science Research Center, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, PR China;1. State Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi''an 710069, China;2. Research Institute No. 203, CNNC, Xianyang, Shanxi, China |
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| Abstract: | Xiaolonghe is a poorly studied greisen-type tin deposit that is hosted by biotite granite in the western Yunnan tin belt. The mineralisation-related metaluminous and weak peraluminous granite is characterised by high Si, Al and K and low Mg, Fe and Ca, with an average A/CNK of 1.02. The granite is enriched in LILEs (K and Rb), LREEs and HFSEs (Zr, Hf, Th, U and Ce) and depleted in Ba, Nb, Sr, P, and Ti, with zircon εHf(t) = ? 10.8 to ? 7.5 (TDM2 = 1.61–1.82 Ga). These characteristics indicate that the magma was generated by the partial melting of a thickened ancient crust. LA-ICP-MS U–Pb dating of igneous zircon and hydrothermal cassiterite yield ages of 71.4 ± 0.4 Ma and 71.6 ± 4.8 Ma, respectively. The igneous biotite and hydrothermal muscovite samples show Ar–Ar plateau ages of 72.3 ± 0.4 Ma and 70.6 ± 0.2 Ma, respectively. The close temporal relationship between the igneous emplacement and hydrothermal activity suggests that the tin mineralisation was closely linked to the igneous emplacement. The δ18O and δD values for the deposit range from + 3.11‰ to ? 4.5‰ and from ? 127.3‰ to ? 94.7‰, respectively. The hydrothermal calcite C and O isotopic data show a wide range of δ13CPDB values from ? 5.7‰ to ? 4.4‰, and the δ18OSMOW values range from + 1.4‰ to + 11.2‰. The δ34SV-CDT data range from + 4.8‰ to + 8.9‰ for pyrite, and the 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios range from 18.708 to 18.760, from 15.728 to 15.754 and from 39.237 to 39.341, respectively. The stable isotopic (C–H–O–S–Pb) compositions are all similar to those of magmatic and mantle-derived fluids, which indicate that the ore-forming fluids and materials were mainly derived from magmatic sources that were accompanied by meteoric water. The tin mineralisation in the Xiaolonghe district was closely associated with the Late Cretaceous crustal-melting S-type granites that formed during the subduction of the Neo-Tethys oceanic lithosphere. Combined with the tin deposits in the Southeast Asian tin belt, Tengchong block and Central Lhasa, we interpreted that a giant intermittent tin mineralisation belt should be present along the Asian Neo-Tethys margin. |
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