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Journal Article

Structural, Petrological, and Chronological Constraints from Eastern India and Implications for the ∼1.0 Ga Assembly of Greater India

Naraga Prabhakar, A. Bhattacharya, M. Sathyanarayanan and P. K. Mukherjee
The Journal of Geology
Vol. 122, No. 4 (July 2014), pp. 411-432
DOI: 10.1086/676459
Stable URL: http://www.jstor.org/stable/10.1086/676459
Page Count: 22

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Topics: Monazites, Shear zones, Schist, Cratons, Mica, Staurolite, Gneiss, Quartz, Tectonics, Chemical composition
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Structural, Petrological, and Chronological Constraints from Eastern India and Implications for the ∼1.0 Ga Assembly of Greater India
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Abstract

AbstractThe Great Proterozoic Fold Belt of India (GIPFOB) is the inferred accretion zone between the North India Block (NIB) and the South India Block (SIB). Mesoscopic structures, phase petrology, and U-Th-Pb (total) monazite ages in the Bangriposi Shear Zone (BSZ) located in the eastern syntaxis of the GIPFOB along the fringe of the Paleo/Mesoarchean Singhbhum Craton (SC) are examined to constrain the time of NIB-SIB assembly. The BSZ at the eastern fringe of the Archean Singhbhum Craton is a NNE-trending west-vergent 0.95–1.0 Ga greenschist-facies (<0.6 GPa at 500° ± 30°C) sinistral-reverse shear zone. The BSZ is dominated by Meso/Neoarchean (2.6–3.1 Ga) cratonic lithologies and an overlying suite of intensely to weakly deformed cobble/granule quartz conglomerates interbanded with quartzite, low-grade phyllites and mafic schist, and gabbro-wehrlite complexes. The precursors to the low-grade conglomerate-phyllite-quartzite sequence and the obducted ultrahigh-pressure (5.3–5.9 GPa at 1200°–1230°C) wehrlite body constitute a 0.95–1.0 Ga tectonic mélange interleaved with cratonic (Archean) lithologies of higher metamorphic grade. The lack of Mesoproterozoic (1.5–1.7 Ga) metamorphism in the BSZ and neighboring areas, which are common along the NW/N margin of the Singhbhum Craton and the accreted southern meta-flysch belt of the North Singhbhum Mobile Belt (NSMB) is significant. It is suggested that the northern meta-flysch belt of the NSMB and the Singhbhum Craton were not juxtaposed until ∼1.0 Ga. These crustal domains were finally accreted during the final stages (0.95–1.0 Ga) of Rodinia supercontinent assembly forming a -shaped ∼1.0 Ga tectonic zone in eastern India. The “Greater India” landmass comprising the NIB and the SIB came into existence during this ∼1.0 Ga global tectonic episode.

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