A Unified Model of Neoarchean-Proterozoic Convergence and Rifting of Indian Cratons: Geophysical Constraints  

作　　者：Dinesh Chandra Mishra 

机构地区：[1]不详

出　　处：《International Journal of Geosciences》2011年第4期610-630,共21页地球科学国际期刊（英文）

摘　　要：Neoarchean and Proterozoic sutures and collision zones are identified in the Indian Peninsular Shield based on high seismic velocity;gravity highs and high conductivity in the upper crust due to thrusting while sub- ducted side are demarcated based on geophysical signatures of crustal thickening and back arc type basins. Some of them appear to form triple junctions. The Bouguer anomaly map of the south Indian shield when transformed to apparent density map through harmonic inversion, provided high density linear zones coin- ciding with the shear zone and the transition zone-the Moyar Bhavani Shear Zone (MBSZ) between the Eastern Dharwar Craton (EDC) and the Western Dharwar Craton (WDC) and the Dharwar cratons and the Southern Granulite Terrain (SGT), respectively. It is supported by high seismic velocity and high conductiv- ity suggesting them to be caused by high grade granulite rocks related to Neoarchean-Paleoproterozoic su- tures and collision zones. These investigations also suggest thick crust (~40 - 50 km) under the WDC and the SGT forming crustal root of 50 - 52 km in the south western part and thin crust of 31 - 32 km under the EDC indicating direction of convergence and subduction as E-W and N-S between the EDC and the WDC and Dharwar cratons and the SGT, respectively. It gave rise to contemporary lower crustal granulite rocks in the northern part of the SGT and Cauvery shear zone (CSZ) as collision related central core complex of various deep seated intrusive rocks of Paleo-Mesoproterozoic period. The second case belonging to Meso-proterozoic period is related to the collision of the Bundelkhand craton and the Bhandara-Bastar craton (BBC) and the Dharwar craton (DC) in Central India along the Satpura Mobile Belt (SMB) and the BBC and the DC along the Godavari Proterozoic Belt due to N-S and NE-SW convergences, respectively. This process has given rise to lower crustal granulite rocks of high density, high velocity and high conductivity along the SMB and the GPB. An upper mantle conductor delineated souNeoarchean and Proterozoic sutures and collision zones are identified in the Indian Peninsular Shield based on high seismic velocity;gravity highs and high conductivity in the upper crust due to thrusting while sub- ducted side are demarcated based on geophysical signatures of crustal thickening and back arc type basins. Some of them appear to form triple junctions. The Bouguer anomaly map of the south Indian shield when transformed to apparent density map through harmonic inversion, provided high density linear zones coin- ciding with the shear zone and the transition zone-the Moyar Bhavani Shear Zone (MBSZ) between the Eastern Dharwar Craton (EDC) and the Western Dharwar Craton (WDC) and the Dharwar cratons and the Southern Granulite Terrain (SGT), respectively. It is supported by high seismic velocity and high conductiv- ity suggesting them to be caused by high grade granulite rocks related to Neoarchean-Paleoproterozoic su- tures and collision zones. These investigations also suggest thick crust (~40 - 50 km) under the WDC and the SGT forming crustal root of 50 - 52 km in the south western part and thin crust of 31 - 32 km under the EDC indicating direction of convergence and subduction as E-W and N-S between the EDC and the WDC and Dharwar cratons and the SGT, respectively. It gave rise to contemporary lower crustal granulite rocks in the northern part of the SGT and Cauvery shear zone (CSZ) as collision related central core complex of various deep seated intrusive rocks of Paleo-Mesoproterozoic period. The second case belonging to Meso-proterozoic period is related to the collision of the Bundelkhand craton and the Bhandara-Bastar craton (BBC) and the Dharwar craton (DC) in Central India along the Satpura Mobile Belt (SMB) and the BBC and the DC along the Godavari Proterozoic Belt due to N-S and NE-SW convergences, respectively. This process has given rise to lower crustal granulite rocks of high density, high velocity and high conductivity along the SMB and the GPB. An upper mantle conductor delineated sou

关 键 词：INDIAN Shield CONVERGENCE Collision Triple Junction and Gravity Anomaly 

分 类 号：P5[天文地球—地质学]