| 澜沧江南带火山岩系侏罗纪火山岩的存在及其地质意义 |
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| 关键词:volcanic rocks in the southern Lancang River belt rhyolite geochemical characteristics chronology geological significance Pu'er area |
| 基金项目:国家重点研发计划(编号: 2016YFC0600306);国家自然科学基金(编号: 41773042; 41922022; 41773043; 41772088; 41472067);自然资源部深地动力学重点实验室自主研究课题(编号: J1901-6);国际地质对比计划(编号: IGCP-662) |
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| The Existence of the Jurassic Volcanic Rocks in the Southern Part of the Lancangjiang Belt and Its Geological Significance |
| The volcanic rock in the south of the Lancang River is a product of the evolution of the Paleo-Tethys and can serve as a tool for inverting the evolution of the Paleo-Tethys. In this paper, the authors selected the systematic chronology and geochemistry of the volcanic rocks in the Nanancun section of the Pu'er area as the study object, which can provide a new understanding of the evolution of the Paleo-Tethys Ocean. The volcanic rock in the area is a rhyolite of plaque-like structure and rhyolite structure. Its phenocrysts are composed of semi-automorphic slab-like K-feldspar and quartz. The matrix is cryptocrystalline feldspar and quartz. The main element analysis shows that the content of SiO2 is 75.59%~77.40%, that of Al2O3 is 11.69%~12.20%, and that of K2O (4.13%) is higher than that of Na2O (3.72%), indicating that the rhyolite is peraluminous high potassium calc-alkaline, calc-alkaline volcanic rock. The CaO/Na2O ratio is 0.01~0.04, Al2O3/(MgO+TFeO) is 0.03~0.06, and CaO/(MgO+TFeO) is 5.51~6.66, the ratio of Nb/Ta is concentrated at 12.27~13.08, with an average of 12.79, and the data of radioactive?isotope 87Sr/86Sr are 0.714~0.719, 207Pb/204Pb are 15.733~15.760, 206Pb/204Pb are 18.903~19.400, indicating that the volcanic source was derived from the remolten (metamorphic) mudstone crust. The standardized trace element distribution curve is irregularly jagged and highly consistent, the data of Rb, Nb, Ta, Y and Yb are rich Rb and low Nb, Ta, Y and Yb, indicating that the volcanic rocks in the southern part of the Lancang River have the property of volcanic rocks in the continent marginal arc. The LA-ICP-MS zircon U-Pb chronology shows that the concordant age of volcanic rocks is (200.6±2.8) Ma. It is consistent with the volcanic rock activity (210–280 Ma) in the northern section of the southern Lancang River belt, indicating that the volcanic activity in the southern Lancang River belt lasted at least to the early Jurassic, that is, the subduction activity of the Paleo-Tethys Ocean lasted at least to the early Jurassic. |
| TANG Bo-lang,LIU Ying-chao,MA Wang,YUE Long-long,HUANG Shi-qiang,ZHUNAG Liang-liang,WU Zhi-yi,ZHOU Meng-lin.2020.The Existence of the Jurassic Volcanic Rocks in the Southern Part of the Lancangjiang Belt and Its Geological Significance[J].Acta Geoscientica Sinica,41(3):357-370. |
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