Evolution of calc-alkaline to alkaline magmatism through Carboniferous convergence to Permian transcurrent tectonics,western Chinese Tianshan |
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Authors: | Bo Wang Dominique Cluzel Liangshu Shu Michel Faure Jacques Charvet Yan Chen Sebastien Meffre Koen de Jong |
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Institution: | 1.State Key Laboratory for Mineral Deposits Research, Department of Earth Sciences,Nanjing University,Nanjing,China;2.ISTO UMR 6113,University of Orléans,Orléans, Cedex 2,France;3.Institute of Earth Sciences,Academia Sinica,Taipei,Taiwan, ROC;4.School of Earth Sciences,University of Tasmania,Hobart,Australia |
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Abstract: | Continuous magmatic activity occurred in the western Chinese Tianshan, Central Asia, from the Carboniferous to the Permian,
i.e. before and after the Late Carboniferous amalgamation of Junggar and the Yili Blocks. Zircon U–Pb LA-ICPMS and Ar–Ar data
reveal a coincidence in time between regional wrench faulting and granitoid emplacement. Permian post-collisional granitoids
crop out within or at the margins of large-scale dextral strike-slip shear zones, some of them show synkinematic fabrics.
The whole rock geochemical features of the Early-Middle Permian granitoids indicate an evolution from high-K calc-alkaline
towards alkaline series. In other places of the North Tianshan, alkaline magmatism occurred together with deep marine sedimentation
within elongated troughs controlled by wrench faults. Therefore, in contrast with previous interpretations that forwarded
continental rift or mantle plume hypotheses, the coexistence of diverse magmatic sources during the same tectonic episode
suggests that post-collisional lithosphere-scale transcurrent shearing tightly controlled the magmatic activity during the
transition from convergent margin to intraplate anorogenic processes. |
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