Geological Features, Ages, and Tectonic Implications of the Wenquan Group in NW Chinese Tianshan
详细信息
- 责任者：Li Kongsen (State Key Laboratory for Mineral Deposits Research ; School of Earth Sciences and Engineering ; Nanjing University ; Nanjing 210093 ; China) ; Wang Bo
- 刊名：Geological Journal of China Universities
- 出版年：2013
- 卷期：19(3)
- 关键词：变质岩 ; metamorphic rocks ; 火成岩 ; igneous rocks ; 天山 ; Tianshan Mountains
- 页码：p.491-503
- 图表：5 illus., 1 table, 90 refs.
- 分类号：0802
- issnNo：ISSN1006-7493
- isbnNo：CN32-1440/P
摘要
The metamorphic rocks of the Wenquan Group in the Northern Chinese Tianshan have been regarded as Paleoproterozoic in age.According to our field observations and zircon SHRIMP U-Pb dating,the Wenquan Group can be subdivided into three lithotectonic units:(1) pre-Early Neoproterozoic meta-volcanic and meta-sedimentary rocks,including amphibolite,micaschist,quartz schist,biotite gneiss and marble;(2) Early Neoproterozoic migmatite and orthogneiss;and(3) undeformed Early Paleozoic gabbro and diorite.All these three units were intruded by two-mica granite or dykes.Migmatite and granitic gneiss collected from the south of Wenquan City yielded zircon SHRIMP U-Pb ages of 926±12 Ma and 907±11 Ma,respectively.These ages are close to those of Neoproterozoic granitoids occurring in the Chinese Tianshan.Previous results of a Nd isotopic study on orthogneiss indicate an origin of partial melting of continental crust,and the occurrences of synchronous migmatite support a thickening and partial melting of continental crust.Gabbro and diorite intruded in the granitc gneiss and amphibolite of the Wenquan Group.A diorite yields a zircon SHRIMP U-Pb age of 452±7 Ma,and contains inherited zircons with older ages of 1.1 Ga and 1.4 Ga.According to the previous studies,the gabbro and diorite have geochemical features of arc-related magmatism,the early Paleozoic arc-type magmatic rocks of the study area were likely formed during subduction of the Junggar-Balkhash Oceanic lithosphere,and the subsequent accretion between the Northern Yili block and the Kazakhstan continent that induced the metamorphism and deformation of the Precambrian metamorphic and magmatic rocks of the Wenquan Group.
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