Early Neoproterozoic Tectonics in the Godhra–Chhota Udepur Sector: Evidence for Two-Stage Accretion in the Great Indian Proterozoic Fold Belt

Abstract

The Great Indian Proterozoic Fold Belt (GIPFOB) is a curviplanar highly-tectonized zone of Precambrian crystalline rocks. In the GIPFOB, the N/NNE-striking western arm (the Aravalli Delhi Fold Belt, ADFB) and the E-striking southern arm consisting of the Chottanagpur Gneiss Complex (CGC) and the central/southern domains of the Satpura Mobile Belt (SMB) converge at the Godhra-Chhota Udepur sector. To investigate the tectonics of the sector, we combine the results of analyses of mesoscale and regional structures, U-Pb (zircon) geochronology, and monazite chemical dating to constrain the convergence. The sector is dominated by an ensemble of shallow-dipping granitoid mylonites (D2 deformation) and recumbently folded anatectic granulite-facies basement gneisses interleaved with allochthonous greenschist/epidote-amphibolite facies supracrustal rocks thrust top-to-the-south. The shallow-dipping carapace is traversed by a network of E-striking steep-dipping shear zones with sinistral and N-down kinematics (D3 deformation). The D3 shear zone hosted granitoids exhibit E-striking suprasolidus deformation fabrics and chessboard microstructures. In the shallow-dipping carapace, the partly overlapping stretching lineations associated with D2-D3 deformations share low-angle obliquities with the W/WNW plunging hinges of D2 recumbent folds and the upright/moderately-inclined D3 folds in the basement gneisses and the supracrustal rocks. The transition from thrust-dominated (D2) to wrench-dominated (D3) deformation involved flipping of Y and Z strain axes for similar orientations of orogen-parallel stretching caused by N-S shortening. U-Pb LA-ICP-MS (zircon) and monazite chemical dates suggest the D2-D3 deformation and felsic plutonism occurred at 0.95–0.90 Ga, the pre-D2 high-grade metamorphism in the anatectic gneisses at 1.7–1.6 Ga. The 0.95–0.90 Ga structures in the Godhra-Chhota Udepur are identical to those in CGC-SMB in the southern arm and terminate the N/NNE-striking structures in the ADFB. We suggest the GIPFOB comprises two Early Neoproterozoic accretion zones, e.g., the western arm (ADFB) and the younger (GC-SMB-CGC) southern arm.

Dynamics of Early Neoproterozoic accretion, west-central India: I. Geochronology and Geochemistry

“…But the common occurrences of chess-board microstructures in quartz suggest the post-D2 granitoids were hot (T> 650 ºC; Kruhl, 1996) J o u r n a l P r e -p r o o f during D3 deformation. Chess-board microstructures in quartz in the post-D2 granitoids are highlighted by several authors (Mamtani and Greiling, 2005;Banerjee et al, 2022a); by contrast the pre-D2 granitoids lack this deformation microstructure. If we therefore combine the mesoscale field relations with the deformation microstructures, the emplacement of the post-D2 granitoids appears to be broadly synchronous with the D3 deformation induced by the N-S convergence, but this deformation outlasted the solidification of the post-D2 granitoids.…”

“…The LA-ICP-MS U-Pb zircon dates obtained in the nine samples, combined with two zircondated samples in Banerjee et al (2022a), may be grouped into four age populations, e.g. 2.5-2.4 Ga, 1.7-1.6 Ga, 1.03-1.02 Ga and 0.95-0.93 Ga (Fig.…”

“…Instead the broad -bend‖ in the The granitoids in the area are dominantly post-D2 to syn-D3; the granitoids occur as lens-shaped bodies, exemplified by the Sanada granitoid pluton (Fig. 2a; Banerjee et al, 2022a). The pre-D2 granitoids cover a smaller area.…”

“…The E-striking southern arm of the GIPFOB, also termed as the Central Indian Tectonic Zone (CITZ) (Sharma, 2009) is sandwiched between the NIB and the South India Block (SIB) consisting of the Archean Cratons of Singhbhum and Bastar. This arm consists of the coherently evolved Late Paleoproterozoic to Early Neoproterozoic crustal domains of the Chottanagpur Gneiss Complex (CGC) and the southern and central domains of the Satpura Mobile Belt (SMB), extending west up to the Godhra-Chhota Udepur sector (Banerjee et al, 2021(Banerjee et al, , 2022a. On the other hand, the N/NNEstriking western arm of the GIPFOB comprises the Neoarchean to Early Neoproterozoic Aravalli Delhi Fold Belt (ADFB) juxtaposed between the Marwar Craton (MC) in the west, and the NIB in the east (Fig.…”

“…1). Banerjee et al (2021Banerjee et al ( , 2022a demonstrate that the curvilinear geometry of the GIPFOB is not due to the bending of a single accretion zone around an -indentor‖ (cf. Weil and Sussman, 2004) such as the Bundelkhand Craton.…”