| Petrology and PGE Abundances of High-Cr and High-Al Podiform Chromitites and Peridotites from the Bulqiza Ultramafic Massif, Eastern Mirdita Ophiolite, Albania |
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| 作者姓名： | QIU Tian YANG Jingsui MILUSHI Ibrahim WU Weiwei MEKSHIQI Nezir XIONG Fahui ZHANG Cong SHEN Tingting |
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| 作者单位： | 1 Center for Advanced Research on the Mantle (CARMA), Key Laboratory of Deep Earth Dynamics of Ministry
of Land and Resources, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China,1 Center for Advanced Research on the Mantle (CARMA), Key Laboratory of Deep Earth Dynamics of Ministry,2 Institute of Geosciences, Energy, Water and Environment, Polytechnic University of TIRANA, Tirana 1000,
Albania,3 Faculty of Earth Sciences, China University of Geoscience, Wuhan 430074, Hubei, China,2 Institute of Geosciences, Energy, Water and Environment, Polytechnic University of TIRANA, Tirana 1000,
Albania,1 Center for Advanced Research on the Mantle (CARMA), Key Laboratory of Deep Earth Dynamics of Ministry
of Land and Resources, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China,1 Center for Advanced Research on the Mantle (CARMA), Key Laboratory of Deep Earth Dynamics of Ministry
of Land and Resources, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China；4 Institute of Geological Science and Engineering, Shandong University of Science and Technology, Qingdao
266510, Shandong, China and 1 Center for Advanced Research on the Mantle (CARMA), Key Laboratory of Deep Earth Dynamics of Ministry
of Land and Resources, Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037, China |
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| 摘 要： | The Bulqiza ultramafic massif, which is part of the eastern Mirdita ophiolite of northern Albania, is world renowned for its high-Cr chromitite deposits. High-Cr chromitites hosted in the mantle section are the crystallized products of boninitic melts in a supra-subduction zone (SSZ). However, economically important high-Al chromitites are also present in massive dunite of the mantle-crust transition zone (MTZ). Chromian-spinel in the high-Al chromitites and dunites of the MTZ have much lower Cr# values (100Cr/(Cr+Al)) (47.7–55.1 and 46.5–51.7, respectively) than those in the high-Cr chromitites (78.2–80.4), harzburgites (72.6–77.9) and mantle dunites (79.4–84.3). The chemical differences in these two types of chromitites are reflected in the behaviors of their platinum-group elements (PGE). The high-Cr chromitites are rich in IPGE relative to PPGE with 0.10–0.45 PPGE/IPGE ratios, whereas the high-Al chromitites have relatively higher PPGE/IPGE ratios between 1.20 and 7.80. The calculated melts in equilibrium with the high-Cr chromitites are boninitic-like, and those associated with the high-Al chromitites are MORB-like but with hydrous, oxidized and TiO2-poor features. We propose that the coexistence of both types of chromitites in the Bulqiza ultramafic massif may indicates a change in magma composition from MORB-like to boninitic-like in a proto-forearc setting during subduction initiation.
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| 收稿时间： | 2020/5/18 0:00:00 |
| 修稿时间： | 2018/4/8 0:00:00 |
Petrology and PGE Abundances of High‐Cr and High‐Al Podiform Chromitites and Peridotites from the Bulqiza Ultramafic Massif,Eastern Mirdita Ophiolite,Albania |
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| Authors: | QIU Tian YANG Jingsui MILUSHI Ibrahim WU Weiwei MEKSHIQI Nezir XIONG Fahui ZHANG Cong and SHEN Tingting |
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| Institution: | 1. Center for Advanced Research on the Mantle (CARMA), Key Laboratory of Deep Earth Dynamics of Ministry of Land and Resources, Institute of Geology, Chinese Academy of Geological Sciences, China;2. Institute of Geosciences, Energy, Water and Environment, Polytechnic University of TIRANA, Albania;3. Faculty of Earth Sciences, China University of Geoscience, Hubei, China;4. Institute of Geological Science and Engineering, Shandong University of Science and Technology, Shandong, China |
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| Abstract: | The Bulqiza ultramafic massif, which is part of the eastern Mirdita ophiolite of northern Albania, is world renowned for its high‐Cr chromitite deposits. High‐Cr chromitites hosted in the mantle section are the crystallized products of boninitic melts in a supra‐subduction zone (SSZ). However, economically important high‐Al chromitites are also present in massive dunite of the mantle‐crust transition zone (MTZ). Chromian‐spinel in the high‐Al chromitites and dunites of the MTZ have much lower Cr# values (100Cr/(Cr+Al)) (47.7–55.1 and 46.5–51.7, respectively) than those in the high‐Cr chromitites (78.2–80.4), harzburgites (72.6–77.9) and mantle dunites (79.4–84.3). The chemical differences in these two types of chromitites are reflected in the behaviors of their platinum‐group elements (PGE). The high‐Cr chromitites are rich in IPGE relative to PPGE with 0.10–0.45 PPGE/IPGE ratios, whereas the high‐Al chromitites have relatively higher PPGE/IPGE ratios between 1.20 and 7.80. The calculated melts in equilibrium with the high‐Cr chromitites are boninitic‐like, and those associated with the high‐Al chromitites are MORB‐like but with hydrous, oxidized and TiO2‐poor features. We propose that the coexistence of both types of chromitites in the Bulqiza ultramafic massif may indicates a change in magma composition from MORB‐like to boninitic‐like in a proto‐forearc setting during subduction initiation. |
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| Keywords: | chromian‐spinel platinum‐group elements high‐Cr and high‐Al chromitite Mirdita ophiolite Albania |
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