Metamorphic evolution of garnet- and kyanite-bearing paragneiss in Dulan area of the North Qaidam Mountains, western China
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    Abstract:

    A high-pressure granulite unit was recognized in Dulan area at the eastern end of the North Qaidam UHP metamorphic belt. The HP granulite unit comprises mafic (felsic) HP granulite, granitic gneiss, pelitic schist (gneiss), garnet amphibolite and tonalite. Based on the petrographic features and metamorphic reaction, mineral chemistry and p-t calculations, the authors divided the paragneiss into four metamorphic stages: Stage Ⅰ, which is the pre-peak prograde metamorphic stage characterized by biotite, muscovite, plagioclase and quartz inclusions within the core of zoned garnet porphyroblasts; Stage Ⅱ, the peak HP granulite-facies metamorphic stage, which is characterized by the mineral assemblage of garnet + kyanite + ternary-feldspar + plagioclase + quartz, with peak p-t conditions of t=800~840℃ and p=1.4~1.6 GPa; Stage Ⅲ, the initial decompressional retrogression began at the high amphibolite-facies stage characterized by garnet + biotite + plagioclase + quartz; Stage Ⅳ, final retrogression under gre enschist-facies conditions was deve loped at shallow crustal levels, characterized by the existence of Ms+Pl±Zo and Mrg+Qtz±Ms±Pl assemblages around kyanite. Zircon LA-ICP-MS U-Pb dating yielded peak HP granulite-facies metamorphic age of 431 Ma. The combination of petrographic textures, mineral compositions and thermobarometric data defined a single clockwise p-t path for the Dulan paragneiss, similar to that of HP mafic granulite.

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于胜尧,张建新,宫江华,李云帅,2014,柴北缘都兰地区含石榴石、蓝晶石片麻岩的变质演化历史[J].岩石矿物学杂志,33(3):441~457. YU Sheng-yao, ZHANG Jian-xin, GONG Jiang-hua, LI Yun-shuai,2014,Metamorphic evolution of garnet- and kyanite-bearing paragneiss in Dulan area of the North Qaidam Mountains, western China[J]. Acta Petrologica et Mineralogica,33(3):441~457.

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History
  • Received:November 06,2013
  • Revised:April 10,2014
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  • Online: May 29,2014
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