Chromite compositions in nickel sulphide mineralized intrusions of the Kabanga-Musongati-Kapalagulu Alignment,East Africa: Petrologic and exploration significance |
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| Institution: | 1. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China;2. The Bureau of Geo-exploration Guangxi and Mineral Development, Nanning 530023, China;3. Trading Center of Land and Resources of Guangxi Zhuang Autonomous Region, Nanning 530023, China;1. Science Research Institute, China University of Geosciences, Beijing, China;2. Department of Earth Sciences, University College London, UK;3. School of Earth Sciences and Engineering, Sun Yat-sen University, Guangzhou, China;4. No.3 Exploration Institute of Geology and Mineral Resources of Qinghai Province, Xining 810029, China;1. Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China;2. School of the Earth and Space Sciences, Peking University, Beijing 100871, China;3. School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083, China;4. Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China;5. China National Geological and Mining Corporation, Beijing 100029, China;6. Huaxia Mining Corporation, Tibet 850000, China;1. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing 100083, China;2. Institute of Gold Geology, Chinese Armed Police Force, Langfang 065000, China |
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| Abstract: | Chromite is a ubiquitous accessory mineral in the olivine-pyroxene cumulate bodies that host massive and disseminated nickel sulphide mineralization in intrusions of the Kabanga-Musongati-Kapalagulu Alignment in East Africa. Its composition is related to the conditions of emplacement and petrologic evolution of its host magma in a spectrum of intrusions ranging from classical lopolithic layered intrusions to groups of smaller, discrete sill-like chonoliths.The Kapalagulu lopolithic intrusion, emplaced into polymetamorphosed Archæan-Palæoproterozoic crust, contains abundant chromite with relatively oxidized compositions, whereas chromites from the highly-mineralized Kabanga chonolith intrusions, emplaced into graphitic and sulphidic schists, are strongly reduced in terms of their Fe3+/Fetotal ratio. Ni in chromite correlates with Ni in olivine: Ni in both is depleted in the more strongly sulphide-mineralized intrusions. The Musongati intrusion, also emplaced through graphitic schists, but much larger and less-well mineralized in sulphides than Kabanga, has chromites intermediate in character. The compositions of the chromites can be used to determine the petrologic history of the intrusions, and may prove to be a useful exploration tool in such mineralized belts. |
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| Keywords: | Kibaran Nickel sulphide Chromite Magma contamination Sulphur saturation Oxygen fugacity |
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