SHRIMP U-Pb dating and Hf isotopic analyses of zircons from the mafic dyke swarms in central Qiangtang area, Northern Tibet |
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Authors: | QingGuo Zhai Cai Li Jun Wang ZhanSheng Ji Yong Wang |
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Affiliation: | (1) Institute of Geology, Chinese Academy of Geological Sciences, Beijing, 100037, China;(2) College of Earth Sciences, Jilin University, Changchun, 130061, China |
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Abstract: | In the “Central Uplift” of Qiangtang, Northern Tibet, a large scale of mafic dyke swarms extended in E-W direction. Zircon SHRIMP U-Pb dating on two representative samples of diabase dyke yield weighted mean ages of 284 ± 3 Ma and 302 ± 4 Ma, respectively, suggesting they emplaced in the Late Carboniferous to Early Permian. Zircon 176Hf/177Hf ratios range from 0.282852 to 0.283041, with ε Hf(t) values of +12.1 to +12.2 and Hf modal (T DM) ages of:_440–460 Ma. These data indicate that these mafic dykes were mainly derived from the depleted mantle. In addition, geochemical data suggest that these mafic dyke swarms are of intra-plate origin. Therefore, the mafic dyke swarms represent products during the extensional process associated with the opening of the Paleo-Tethys Ocean in the area. Supported by National Natural Science Foundation of China (Grants Nos. 40872146 and 40672147) and China Geological Survey (Grant No. 1212010561605) |
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Keywords: | Northern Tibet Qiangtang mafic dyke swarm SHRIMP dating Hf isotope |
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