In order to constrain whether the Lhasa–Qiangtang collision contributed to an early crustal thickening of the central Tibetan Plateau prior to the India–Asia collision,we present zircon LA–ICP–MS U–Pb ages,wholer...In order to constrain whether the Lhasa–Qiangtang collision contributed to an early crustal thickening of the central Tibetan Plateau prior to the India–Asia collision,we present zircon LA–ICP–MS U–Pb ages,wholerock geochemistry,and zircon Hf isotopic compositions of the newly discovered rhyolitic crystal tuffs from the Chuduoqu area in the eastern Qiangtang subterrane,central Tibet.Zircon U–Pb dating suggests that the Chuduoqu rhyolitic crystal tuffs were emplaced at ca.68 Ma.The Chuoduoqu rhyolitic crystal tuffs display high SiO_(2) and K2 O,and low MgO,Cr,and Ni.Combined with their zircon Hf isotopic data,we suggest that they were derived from partial melting of the juvenile lower crust,and the magma underwent fractional crystallization and limited upper continental crustal assimilation during its evolution prior to eruption.They should be formed in a post-collisional environment related to lithospheric mantle delamination.The Chuduoqu rhyolitic crystal tuffs could provide important constraints on the Late Cretaceous crustal thickening of the central Tibetan Plateau caused by the Lhasa–Qiangtang collision.展开更多
A comprehensive petrographic observation contributes to classification of various textures in welded tuffs into two types, the textures in plastic fragments and the ones in rigid fragments. A detailed petrographic stu...A comprehensive petrographic observation contributes to classification of various textures in welded tuffs into two types, the textures in plastic fragments and the ones in rigid fragments. A detailed petrographic study of the textures in plastic fragments leads to suggestion that thesetextures are not a type of devitrification textures. and also that they were formed not by devitrification but by undercooling crystallization. This viewpoint is supported by results of undercooling crystallization experiments. The petrographic characteristics of these textures are satisfactorily demonstrated by the undercooling crystallization theory.展开更多
基金funded by the National Natural Science Foundation of China(41272093)the Geological Survey Project(12120114080901)of China Geological Survey+4 种基金the Self-determined Foundation of Key Laboratory of Mineral Resources Evaluation in Northeast Asia,Ministry of Natural Resources(DBY-ZZ-19-04)the Shandong Provincial Natural Science Foundation of China(No.ZR2019PD017)the Natural Science Foundation of Liaoning Province(2020-BS-258)the Department of Education of Liaoning Province(LJ2020JCL010)a Discipline Innovation Team Project of Liaoning Technical University(LNTU20TD-14)。
文摘In order to constrain whether the Lhasa–Qiangtang collision contributed to an early crustal thickening of the central Tibetan Plateau prior to the India–Asia collision,we present zircon LA–ICP–MS U–Pb ages,wholerock geochemistry,and zircon Hf isotopic compositions of the newly discovered rhyolitic crystal tuffs from the Chuduoqu area in the eastern Qiangtang subterrane,central Tibet.Zircon U–Pb dating suggests that the Chuduoqu rhyolitic crystal tuffs were emplaced at ca.68 Ma.The Chuoduoqu rhyolitic crystal tuffs display high SiO_(2) and K2 O,and low MgO,Cr,and Ni.Combined with their zircon Hf isotopic data,we suggest that they were derived from partial melting of the juvenile lower crust,and the magma underwent fractional crystallization and limited upper continental crustal assimilation during its evolution prior to eruption.They should be formed in a post-collisional environment related to lithospheric mantle delamination.The Chuduoqu rhyolitic crystal tuffs could provide important constraints on the Late Cretaceous crustal thickening of the central Tibetan Plateau caused by the Lhasa–Qiangtang collision.
文摘A comprehensive petrographic observation contributes to classification of various textures in welded tuffs into two types, the textures in plastic fragments and the ones in rigid fragments. A detailed petrographic study of the textures in plastic fragments leads to suggestion that thesetextures are not a type of devitrification textures. and also that they were formed not by devitrification but by undercooling crystallization. This viewpoint is supported by results of undercooling crystallization experiments. The petrographic characteristics of these textures are satisfactorily demonstrated by the undercooling crystallization theory.
