(2020) Mesozoic Mantle-Crust Interaction in the Eastern Tianshan, Southern of the Central Asian Orogenic Belt
Lei R & Wu C
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04j: Room 1, Saturday 27th June 05:45 - 05:48
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Thank you so much! You think the Eastern Tianshan area belongs to within-plate granites during the Triassic period. Are there Triassic bimodal magmatic rocks or A-type granites? How to explain the characteristics of depletion of high field strength elements (e.g., Nb, Ta) of the Triassic granites in geochemical patterns?
Thank you for your interesting question, Prof. Ma. Firstly, there is a general consensus that the closure of the Paleo-Asian ocean took place from the late Carboniferous to early Permian in the Eastern Tianshan (Xiao et al., 2004; Gu et al., 2006; Chen et al., 2011; Zhang et al., 2016a; Wang et al., 2018). Thus, the Triassic Eastern Tianshan must have been under a post-collisional setting or an intra-continental tectonic setting. Triassic A-type granitoids have been reported in the Eastern Tianshan and adjacent Beishan area and suggested that they formed in an extensional setting (Li et al., 2012; Sun et al., 2017). This inference is also supported by the presence of coeval lamprophyres and many mafic-intermediate dykes in the Eastern Tianshan and adjacent area which are thought to form in lithospheric extension environment (Wang et al., 2008). The subduction-related geochemical characteristics were most likely inherited from the sources that had been metasomatized by subduction-related fluids, as evidenced by the coeval Weiya gabbro nearby also characterized by the same arc-like geochemical features and the lithospheric or asthenospheric mantle sources metasomatized by subducted fluids (Zhang et al., 2007).
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