| 拉萨地体南缘桑日地区晚白垩世火山岩的年代学、岩石地球化学及成因 |
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| 关键词:southern margin of the Lhasa Terrane Sangri area Late Cretaceous Neo-Tethys ocean volcanic rocks |
| 基金项目:四川省科技计划项目(编号: 2020JDJQ0042);国家自然科学基金(编号: 41502079; 41972084);国家重点研发计划课题(编号: 2018YFC0604105);成都理工大学珠峰科学研究计划(编号: 2020ZF11047);西北大学大陆动力学国家重点实验室开放基金(编号: 18LCD04);自然资源部深地资源成矿作用与矿产预测重点实验室开放基金(编号: ZS1911);中国地质调查局项目(编号: DD20190167; DD20160346) |
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| Chronology, Geochemical Characteristics, and Genesis of Late Cretaceous Volcanic Rocks in Sangri Area, Southern Margin of the Lhasa Terrane |
| Intermediate-acid volcanic rocks are widely exposed in the Sangri area of the southern margin of Lhasa terrane. The superposition of multiple magmatic activities over a long formation time has made the composition of magmatic rocks in the area complex. To study the formation age, tectonic setting, and genetic mechanism of volcanic rocks in this area, we selected the intermediate-acid volcanic rocks near Tamu Village in the west of Sangri County as the research object, conducted zircon U-Pb dating, and analyzed whole rock major and trace elements and Sr-Nd isotopes. The SiO2 and MgO contents in Late Cretaceous volcanic rocks in the Sangri area were 55.79%~74.26% and 1.31%~4.34%, respectively. In addition, they have high Sr (average 779×10–6), low Y (8.36~15.85)×10–6 and Yb (0.92~ –1.38)×10–6, and a high Sr/Y ratio (36.28~05.59). Geochemical characteristics showed that the Late Cretaceous volcanic rocks in the Sangri area are adakite rocks. Moreover, the Late Cretaceous Sangri volcanic rocks are enriched in large ion lithophile elements (LILE), such as Rb, Sr, and Pb, and depleted in high field strength elements (HFSE), such as Nb, Ta, and Ti, with low initial values of 87Sr/86Sr (0.704 152~0.704 515) and high initial values of 143Nd/144Nd (0.512 676~0.512 750). Based on petrogeochemical characteristics and regional geological data, the Late Cretaceous volcanic rocks in the Sangri area formed in an active continental margin environment related to the northward subduction of the Neo-Tethyan oceanic crust and were produced by the partial melting of the Neo-Tethyan oceanic crust. The rising process of ocean crust melting was accompanied by the addition of mantle wedge material, which led to fractional crystallization. |
| YANG Tong-shan,LANG Xing-hai,WANG Xu-hui,DENG Yu-lin,LÜ Na,DONG Mi,HE Qing,ZHANG Xiang-guo,LIANG Hai-hui.2023.Chronology, Geochemical Characteristics, and Genesis of Late Cretaceous Volcanic Rocks in Sangri Area, Southern Margin of the Lhasa Terrane[J].Acta Geoscientica Sinica,44(3):467-484. |
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