Mineral chemistry, P-T-t paths and exhumation processes of mafic granulites in Dinggye, Southern Tibet.docx

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1、Mineral chemistry, P-T-t paths and exhumation processes of mafic granulites in Dinggye, Southern TibetThe mafic granulites in Dinggye, as various scale lense-shaped enclaves within the high Himalayan crystalline rock series, occur along mylonitic foliations at the junction between the Southern Tibet

2、an Detachment System (STDS) and the Xainza-Dinggye normal fault system. The main lithological assemblage comprises garnet plagioclase pyroxenite, garnet two-pyroxene granulite, pyroxene garnet amphibolite and so on. The detailed petrological analyses show that these mafic granulites underwent at lea

3、st four-stage metamorphic evolution. The first metamorphic stage, the garnet+clinopyroxene+quart mineral assemblage (M1) was probably formed under eclogite facies, the second stage, the plagioclase+clinopyroxene symplectite mineral assemblage (M2) was produced under high-pressure granulite facies by

4、 the early decompressive breakdown of M1 mineral assemblage, the third stage, the plagioclase+clinopyroxene+ hypersthene symplectite mineral assemblage (M3) was formed at granulite facies by the late period decompressive breakdown of M1 and M2 mineral assemblages and the final stage, plagioclase+hor

5、nblende mineral assemblage (M4) was formed by hydrolysis of earlier mineral assemblages during late uplifting. The detailed mineral composition analyses suggest that garnets and clinopyroxenes within M1 and M2 mineral assemblages display similar compositions to the equivalents in the B and C types o

6、f eclogites, whereas the M3 clinopyroxenes are akin to these of the same kind of minerals in the granulite. These mineral chemistry features and P-T estimates calculated by mineral thermometers and barometers indicate that the early stage relic porphyroblasts (M1) could be formed at the eclogite fac

7、ies, the early decompressive breakdown (M2) occurred at the high-pressures granulite facies of 1.351.48 GPa and 625675, the M3 mineral assemblage recorded the granulite facies of 0.70.95 GPa and 775900 and M4 plagioglase+hornblende retrograde mineral assemblage was produced under the amphibolite fac

8、ies metamorphism with pressure of 0.4 to 0.75 GPa and temperature at between 660 and 700. These construct P-T paths from crustal subduction overthickening to tectonic uplift tectonothermal evolution. The mineral chemical characteristics and P-T condition at every metamorphic stage of these granulite

9、s indicate that these rocks experienced the eclogite facies metamorphism during the early stage. Subsequently, these mafic granulites underwent the three-stage exhumation of the eclogite facies tectonic uplift, isostatic uplift related to the transformation from eclogite/high-pressure granulite to g

10、ranulite facies and extensional uplift.作 者：LIU Shuwen ZHANG Jinjiang SHU Guiming LI Qiugen 作者单位：The Key Laboratory of Orogenic Belts and Crustal Evolution, Ministry of Education, School of Earth and Space Sciences, Peking University, Beijing 100871, China刊 名：中国科学D辑（英文版） SCI英文刊名：SCIENCE IN CHINA (EAR

11、TH SCIENCES)年，卷(期)：200548(11)分类号：P5关键词：mafic granulites garnet and clinopyroxene metamorphic P-T conditions eclogite facies metamorphism three-stage exhumation Dinggye in Southern Tibet本文来源：网络收集与整理，如有侵权，请联系作者删除，谢谢！第4页 共4页第 4 页 共 4 页第 4 页 共 4 页第 4 页 共 4 页第 4 页 共 4 页第 4 页 共 4 页第 4 页 共 4 页第 4 页 共 4 页第 4 页 共 4 页第 4 页 共 4 页第 4 页 共 4 页