Tectonic juxtaposition of crust and continental growth during orogenesis: Example from the Rengali Province, eastern India  

作　　者：Sankar Bose Susmita Guha Gautam Ghosh Kaushik Das Joydip Mukhopadhyay 

机构地区：[1]Department of Geology, Presidency University [2]Department of Earth and Planetary Systems Science, Hiroshima University [3]PPM Research Group, Department of Geology, University of Johannesburg

出　　处：《Geoscience Frontiers》2015年第4期537-555,共19页地学前缘（英文版）

基　　金：financial support from CSIR;India through a major research scheme(No.24(0312)/10/EMR-II);UGC-CAS facility and the DSTFIST facility of the Department of Geology,Presidency University

摘　　要：The southern houndary of the Singhbhum Craton witnessed multiple orogenies that juxtaposed thin slice of granulite suite of the Rengali Province against the low-grade granite-greenstone belt of the craton along the E-W trending Sukinda Thrust. The strong southerly dipping mylonitic foliation within the granulites along with the pronlinent down-dip mineral lineation, suggest a northerly-verging thrusting. Mylonitized charnockite at the contact zone contains enclaves of mafic and ultranlafic granulite, whereas granitoid gneiss contains enclaves of pelitic granulite. Mafic granulite enclaves preserve an early （SiM） foliation that formed during DiM deformation. This rock, along with the host charnockite, were intensely deformed by the D2M thrusting event and resulting S2M foliation development in both rock suites. Geothermobaronietric and pseudosection analyses show that the garnet-clinopyroxene-plagioclase- orthopyroxene-ihllenite-quartz assemblage in mafic granulite was stabilized at high-pressure and temperature conditions （10 12 kbar, 860 C） and was overprinted by a fine-grained assemblage of cli- nopyroxene-plagioclase J hornblende that developed during deconlpression （down to 5.5-7.5 I〈bar）. Matrix hornblende shows incipient breakdown to garnet-clinopyroxene-quartz intergrowth due to a granulite facies reworking. A contrasting P-T history is preserved in the pelitic granulite. The peak assemblage garnet-orthopyroxene-cordierite-quartz-rutile was stabilized at -6.0 kbar, 730 C which resulted flom heating of the mid crust magma during the D2M thrusting. The contrasting P-T histories could result flonl the tectonic juxtaposition of lowerand mid-crustal section during the D2M event. Evidences of an early orogenic imprint within the mafic granulite imply involvement of deep continental crust during southward growth of the Singhbhum Craton.The southern houndary of the Singhbhum Craton witnessed multiple orogenies that juxtaposed thin slice of granulite suite of the Rengali Province against the low-grade granite-greenstone belt of the craton along the E-W trending Sukinda Thrust. The strong southerly dipping mylonitic foliation within the granulites along with the pronlinent down-dip mineral lineation, suggest a northerly-verging thrusting. Mylonitized charnockite at the contact zone contains enclaves of mafic and ultranlafic granulite, whereas granitoid gneiss contains enclaves of pelitic granulite. Mafic granulite enclaves preserve an early （SiM） foliation that formed during DiM deformation. This rock, along with the host charnockite, were intensely deformed by the D2M thrusting event and resulting S2M foliation development in both rock suites. Geothermobaronietric and pseudosection analyses show that the garnet-clinopyroxene-plagioclase- orthopyroxene-ihllenite-quartz assemblage in mafic granulite was stabilized at high-pressure and temperature conditions （10 12 kbar, 860 C） and was overprinted by a fine-grained assemblage of cli- nopyroxene-plagioclase J hornblende that developed during deconlpression （down to 5.5-7.5 I〈bar）. Matrix hornblende shows incipient breakdown to garnet-clinopyroxene-quartz intergrowth due to a granulite facies reworking. A contrasting P-T history is preserved in the pelitic granulite. The peak assemblage garnet-orthopyroxene-cordierite-quartz-rutile was stabilized at -6.0 kbar, 730 C which resulted flom heating of the mid crust magma during the D2M thrusting. The contrasting P-T histories could result flonl the tectonic juxtaposition of lowerand mid-crustal section during the D2M event. Evidences of an early orogenic imprint within the mafic granulite imply involvement of deep continental crust during southward growth of the Singhbhum Craton.

关 键 词：Singhbhunl cratonRengali Province Granulite enclave Tectonic juxtaposition 

分 类 号：P542[天文地球—构造地质学]