U-Pb Ages of Zircons from Ophiolite and Related Rocks in the Kumishi Region at the Southern Margin of Middle Tianshan, Xinjiang: Evidence of Early Paleozoic Oceanic Basin
详细信息
- 责任者：Yang Jinsui (Key Laboratory of Continental Dynamics ; Ministry of Land and Resources ; Institute of Geology ; Chinese Academy of Geological Sciences ; Beijing 10037 ; China) ; Xu Xiangzhen
- 刊名：Acta Petrologica Sinica
- 出版年：2011
- 卷期：27(1)
- 关键词：蛇绿岩 ; ophiolite ; 铀—铅计时 ; U-Pb dating ; 天山 ; Tianshan Mountains
- 页码：p.77-98
- 图表：17 illus., 6 tables, 46 refs.
- 分类号：0801
- issnNo：ISSN1000-0569
- isbnNo：CN11-1922/P
摘要
The Yushugou and Tonghuashan ophiolitic mélange,which occurs in the Kumishi region at the southern margin of the Middle Tianshan Mountains, Xinjiang, consists of mantle peridotite, cumulate pyroxenite, gabbro and anorthosite, diabase dikes and mafic lavas overlain by chert. Geochemical data indicate that the ophiolitic units originated in both MORB and SSZ tectonic settings. U-Pb isotope ages of zircons from the ophiolitic and related rocks record at least four tectonic events related to oceanic spreading and basin closure: 1) ocean basin formation in the Ordovician-Silurian; 2) island arc magmatism in the Silurian; 3) shearing in the Devonian (400 Ma for mylonite); and 4) extensional magmatism of the orogen in the Late Carboniferous (294.8±1.2 Ma for quartz syenite porphyry that formed perpendicular to the direction of subduction and collision).