Chondritic osmium isotopic composition of Archean ophiolitic mantle, North China craton |
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| Authors: | Timothy M Kusky Xiachen Zhi Jianghai Li Qiongxia Xia Tsilavo Raharimahefa Xiongnan Huang |
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| Institution: | aDepartment of Earth and Atmospheric Sciences, St. Louis University, St. Louis MO USA 63103;bSchool of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China;cDepartment of Geology, Peking University, Beijing 100871, China |
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| Abstract: | Podiform chromitites are diagnostic but rare features of Phanerozoic ophiolites, and often contain the most pristine textural, chemical and isotopic record of convective upper mantle conditions extant during ophiolite genesis. Ophiolitic podiform chromitites, owing to their high Os concentrations and low Re/Os ratios provide the best evidence for the Os-isotopic evolution of oceanic mantle, but established records of ophiolitic chromites from bona fide Archean ophiolites are still lacking. We report Re–Os isotopic compositions of the world's oldest known ophiolitic podiform chromites from the 2.5 billion year old Dongwanzi–Zunhua ophiolite, North China. This provides the oldest Os isotope composition for the convective upper mantle yet obtained from ophiolitic podiform chromitites, and reveals a chondritic Os isotopic composition of the Archean convective upper mantle. |
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| Keywords: | Re– Os Archean ophiolite Chromitite Chondritic Convective upper mantle |
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