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摘要
The distribution of Permian-Triassic magmatic rocks in western Yunnan Province is still unclear, resulting in controversy regarding the Paleo-Tethyan tectonic evolution model. Here, we present new LA-ICP-MS zircon U-Pb, zircon Hf isotopes whole-rock major and trace element, and Sr-Nd isotopic data for the Shuixie grabbos of the western Langping-Simao basin in the Sanjiang Orogcn, SW China. The zircon U-Pb ages of two samples from Shuixie gabbros arc 237. 8 + 3. 4 Ma and 240. 8 + 3. 3 Ma respectively, representing their crystallization age and belonging to the Middle Triassic. The samples have high Na 2 0/ K20 (3.81-49. 14), and arc enriched in LILEs (such as Ba, Rb, Th, U), depleted in HFSEs (such as Nb, Ta). The REEs arc weakly fractionated, and the LREEs arc weakly enriched. The SEu values ranges from 0. 87 to 1. 07, without obvious Eu anomaly. Zircon eHr(f) values arc all positive, mainly ranging from +5. 67 to +15. 75. The initial ' Sr/ Sr ratio of the whole rock ranges from 0. 70453-0. 70776, and EnjG) values are all positive, ranging from +4. 9 to +5. 2. Geochemical characteristics show that Shuixie gabbros originated from the partial melting of the depleted mantle, and the fractional crystallization of mafic minerals and Fc-Ti minerals occurred during the magmatic evolution. Shuixie gabbros are located at the junction of the Jiangda-Wcixi arc and the Yunxian arc, and occurs in the continental margin arc environment. These dykes, together with the Zadoi arc, the Jiangda-Wcixi arc and the Yunxian arc, are the products of the subduction of the Paleo-Tethys main ocean basin, thus forming an arc magmatic belt with a length of tens of thousands of kilometers. ? 2023 Geological Society of China.
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