Zircon U-Pb Age and Geochemistry of Jiangdong Intrusion and Its Tectonic Implications in the Mangshi, Western Yunnan Province
详细信息
- 责任者：Zou Guangfu (Chengdu Institute of Geology and Mineral Resources ; Chengdu 610082 ; China) ; Mao Ying
- 刊名：Acta Geologica Sinica
- 出版年：2013
- 卷期：87(11)
- 关键词：花岗岩 ; granite ; 铀—铅计时 ; U-Pb dating ; 云南 ; Yunnan Province
- 页码：p.1635-1646
- 图表：12 illus., 2 tables, 49 refs.
- 分类号：0801
- issnNo：ISSN0001-5717
- isbnNo：CN11-1951/P
摘要
The Jiangdong granites are located in the Jiangdong-Xiangqiu of Mangshi,the western yunnan Tengchong block.Field investigation has found that the Jiangdong intrusion consists of biotite monzo-granite.Most of the Jiangdong granites is from the original Gaoligong Group disintegration by the author through the 1∶50000regional geological mapping.To limit the precise age of the Cenozoic magmatic mineralization in the Mangshi area,the Jiangdong granites have been analyzed using LA-ICP-MS zircon U-Pb techniques and geochemical methods.The zircon LA-ICP-MS dating indicates that the biotite monzo-granites was emplaced at 58.29±0.44Ma.The granite mass is formed in the Paleocene.Geochemical data show that the Jiangdong granites are potassic basalt to high-K cale-alkaline series,characterized by medium content of SiO2(68.66%~73.50%),high K(K2O/Na2O=1.87~2.20)and peraluminous ratio(A/CNK)=0.97~1.36).The biotite monzo-granites is riched in Th,U,Rb and Ba,and depletion in Tb,Nb,Zr and Hf,belong to k black to high-K cale-alkaline peraluminous S-type granites.which are similar to calc-alkaline rocks in island arc or active continental margin.TheΣREE ranges from 158.85×10-6~304.26×10-6,REE diagram shows rightward incline and obvious negative Eu abnormity.Magma source is probably rising and emplacement of partially melt granitic magma dominated by greywacke,which is typical of crustal genesis.Magma source is probably rising and emplacement of partially melt granitic magma dominated by greywacke,which is typical of crustal genesis.The Jiangdong biotite monzo-granite was derived from partial melting ofthe Mid-Proterozoic metamorphosed basement(Gaoligong Group)。According to geochemistry and the trace element discrimination diagrams for tectonic interpretation,the the Cenozoic granitoids are considered to be of the post-collision type formed in a transitional tectonic setting from the compressional system to the tensional system.The Jiangdong granites probably formed in a post-collisional setting,which may imply that the Indian plate collided with the Gangdese-Bomi-Tengchong block before 60 Ma(prior to Cenozoic).The Gangdese-Tengchong tectonic belt entered the tensional stage.The Gangdese-Tengchong block tectono-magmatic orogenesis was intimately related to the closure and subduction and collide orogenesis of the new-Tethys Sea.The determination of the Jiangdong granites’ s crystallization provides new evidence for the Cenozoic tectonic evolution of the Tengchong massif.