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

The Journal of Geology (2014)

N. Prabhakar A. Bhattacharya M. Sathyanarayanan Pulok K. Mukherjee

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Abstract:

The 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.

Keywords:

Greenschist

Dharwar Craton

Greenstone belt

Phyllite

Topics:

Geological and Geochemical Analysis

High-pressure geophysics and materials

earthquake and tectonic studies

10.1086/676459

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