The Greater India Proterozoic Fold Belt, India: Its enigmatic curvature in west-central India, and implications for tectonic evolution in the belt

Abstract:

The Greater India Proterozoic Fold Belt (GIPFOB) is a curviplanar belt of Neoarchean to Early Neoproterozoic magmatic and metamorphic rocks extending across central and northern India. The ensemble of multiply-deformed high grade anatectic gneisses and middle amphibolite facies supracrustal rocks, granitoids of varying ages and mantle derived rocks in the GIPFOB encompasses the Chottanagpur Gneiss Complex (CGC) in the east, the Satpura Mountain Belt (SMB) in the central segment, and the Aravalli Delhi Fold Belt (ADFB) in the north. The GIPFOB is deemed to be the zone of accretion between the North India Block (represented by the Archean Bundelkhand Craton) and the South India Block comprising the Archean Singhbhum and Dharwar cratons.

In the west-central part of India, the Mesozoic Deccan basalts overlie and partly obscure the GIPFOB where it supposedly swings from E-striking in the east to NNE-striking in the north; this impedes an assessment of the structural continuity of the curviplanar belt along its strike. Also recent research demonstrates major differences that exist between the different crustal domains, e.g. the CGC, the SMB and the ADFB, within the GIPFOB. Most notable is the expansive Mid Mesoproterozoic (1.4‒1.5 Ga) ferroan A-type peraluminous felsic magmatism, and the Early Neoproterozoic accretion related nucleation of extensive shallow-dipping foliation and recumbent folding in the CGC. These features are lacking or yet to be identified in the other two crustal domains. Apparently, the tectonism within the GIPFOB may have been non-uniform.

Finally, an enigmatic issue of the GIPFOB is the origin of its pronounced curvature in west-central India. This issue and its relevance to the tectonic evolution of the GIPFOB have never been addressed. Did the curvature in the otherwise coherently evolved GIPFOB occur as a result of a pre-existing indentation? Did the curvature occur as a consequence of rotation of the NNE-striking ADFB against the E-striking CGC-SMB composite continuing westward, but presently obscured by the Deccan volcanics? If not, do the two strands, e.g. the ADFB and the CGC-SMB composite constitute a splay in a transpressional deformation regime? Accordingly, we propose several plausible tectonic models, within the framework of the available data base that needs to be critically examined.