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Isotopic characteristics of shoshonitic rocks in eastern Qinghai-Tibet Plateau: Petrogenesis and its tectonic implication Isotopic characteristics of shoshonitic rocks in eastern Qinghai-Tibet Plateau: Petrogenesis and its tectonic implication |
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| Authors: | ZHANG Yuquan XIE Yingwen LI Xianhua QIU Huaning LIANG Huaying LI Jianping ZHAO Zhenhua DENG Wanming CHUNG Sunlin |
| Institution: | 1. Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China 2. Institute of Geology, Chinese Academy of Sciences, Beijing 100029, China 3. Department of Geology, Taiwan University, Taibei 106-17 |
| Abstract: | The Cenozoic magmatic rocks of shoshonitic series in the easternQinghai-Tibet Plateau include potassic alkaline plutonic rocks, volcanic rocks, lamprophyres and acidic porphyries. Analytical results show that these different lithological rocks are extremely similar in Sr, Nd and Pb isotopic compositions with the range of 0.705 187-0.707 254 for 87Sr/86Sr, 0.512 305-0.512 630 for 143Nd/144Nd, 18.53-18.97 for 206Pb/204Pb, 15.51-15.72 for 207Pb/204Pb and 38.38-39.24 for 208Pb/204Pb. They are isotopically similar to the EMII end-member. This indicates that mantle metasomatism must have taken place in their source region. The formation of these particular rocks is related to crustal thinning and mantle upwelling in a large-scale strike-slip and pull-apart fault zone at about 40 Ma in northern and eastern Qinghai-Tibet Plateau. |
| Keywords: | isotopic characteristics magmatic rocks shoshonitic series eastern Qinghai-Tibet Plateau |
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