Chronological and Geochemical Study of the Cenozoic Potassic Felsic Igneous Rocks in Western Yunnan,SE Tibet:Implications for their Tectonic Mechanisms  

作　　者：TANG Wanli CHEN Jianlin TAN Rongyu 

机构地区：[1]State Key Laboratory of Isotope Geochemistry,Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640,China [2]College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100083,China [3]CAS Center for Excellence in Deep Earth Science,Guangzhou 510640,China

出　　处：《Acta Geologica Sinica(English Edition)》2022年第3期904-918,共15页地质学报（英文版）

基　　金：financially supported by the Ministry of Science and Technology of the People’s Republic of China (Grant Nos. 2020YFA0714804,2019QZKK0703);Natural Science Foundation of China (Grant Nos. 41873037,92055206)

摘　　要：Whether there is a relationship between widespread Cenozoic igneous rocks and the activated Ailao Shan-Red River shear zone(ASRR)in western Yunnan,SE Tibet,remains highly controversial.New geochronological,and geochemical data derived from Cenozoic igneous rocks both within and far from the ASRR offers answers.Although these coeval felsic rocks(36.9-33.5 Ma)are enriched in large-ion lithophile elements relative to high field strength elements,they also display some special geochemical features,such as high Y and Yb values of syenitic porphyries,which contrast with the high Sr and low Y contents of monzoporphyries and granitic porphyries.The syenitic porphyries exhibit geochemical characteristics similar to those of coeval mafic magmas,e.g.,high K 2 O,Y,and Yb contents,indicating that the former were probably generated by fractional crystallization of the latter.However,the high Sr/Y(56.1-109)monzoporphyries and granitic porphyries,combined with their low MgO,and Cr(or Ni)contents,suggest that they were mainly derived from partial melting of a thickened mafic lower crust.Given that these Cenozoic magmatic events exhibiting planar distributions occurred outside of the activation of the ASRR(31-20 Ma),then they were not controlled by the latter.Instead,they were tied to convective removal of a thickened lower lithospheric mantle in western Yunnan during the Paleogene.

关 键 词：GEOCHRONOLOGY geochemistry igneous rocks CENOZOIC Ailao Shan-Red River shear zone Yunnan Province 

分 类 号：P588.1[天文地球—岩石学] P597.3[天文地球—地质学] P534.6