Dynamics, EPMA Th‐U‐Total Pb Monazite Geochronology and Tectonic Implications of Deformational Fabric in the Lower‐Middle Crustal Rocks: A Case Study of Ambaji Granulite, NW India

Abstract

Strain fabric and monazite microstructure were studied and dated by Electron Probe Microanalyser (EPMA) in situ Th‐U‐total Pb monazite geochronology in the Ambaji granulite, South Delhi terrane, NW India. The Ambaji granulite comprises pelitic, calcareous, and mafic granulites with several phases of granite intrusions, G0‐3. The granulites were deformed by three phases of folding, F1–3, during South De lhi orogeny and marked by a subhorizontal pervasive fabric, S1, axial planar to isoclinal‐recumbent F1 folds that developed during granulite facies metamorphism. S1 is overprinted by discrete sets of subvertical shear zones associated with a mylonitic fabric, S2, that were developed axial planar to NE‐SW striking upright F2 folds and facilitated exhumation of granulite facies rocks to the upper crust. The shear zones show early history of high‐temperature thrust sense shear and late stage low‐temperature sinistral shear. The NW‐SE striking F3 folds also affected the granulite facies rocks resulting in interference patterns and variations in regional structural trends. Brittle strike slip, and normal fault (Sf fabric) that developed post F3, led the final exhumation of the granulite facies rocks to the surface. The S1 monazites are Y‐depleted and recrystallized through dislocation creep, and the S2‐Sf monazites are Y‐enriched and recrystallized through dissolution‐precipitation creep. Different monazite population yielded distinct ages of circa 875‐857, 834‐778, and 764‐650 Ma for S1, S2, and Sf strain, respectively, indicating that the South Delhi orogeny spanned 875‐650 Ma overlapping with the early phase of the Pan‐African orogeny or representing a transition between Grenvillian and Pan‐African orogeny.

Mid‐Neoproterozoic Tectonics of Northwestern India: Evidence of Stitching Pluton along 810 Ma Phulad Shear Zone

“…The position and participation of the Greater India landmass within the Rodinia supercontinent has been widely questioned (Bhattacharya et al, ; Dalziel, ; Gregory et al, ; Hoffman, ; Kröner & Cordani, ; Li et al, , ; Malone et al, ; Mezger & Cosca, ; Moores, ; Pisarevsky et al, ; Powell & Pisarevsky, ; Radhakrishna & Mathew, ; Torsvik et al, ; Torsvik, Ashwal, et al, ; Torsvik, Carter, et al, ; Weil et al, ). In this connection the tectonics of northwestern India has been extensively discussed and debated (Buick et al, ; Bhowmik et al, ; Chatterjee et al, ; Deb et al, ; Pandit et al, ; Singh et al, ; Tiwari & Biswal, ). Palaeomagnetic studies in the ~750 Ma Malani Igneous Suite (MIS) (Eby & Kochhar, ; Pandit et al, ; Pareek, ; Torsvik, Carter, et al, ) in the Marwar craton suggest that MIS‐Seychelles‐North Madagascar was a coherent terrane separated from the remaining parts of the present‐day Peninsular India at ~750 Ma (Torsvik, Ashwal, et al, ; Torsvik, Carter, et al, ; Tucker et al, ).…”

Petrological implications of element redistribution during metamorphism: insights from meta-granite of the South Delhi Fold Belt, Rajasthan, India

“…The tectonics of northwestern India (Deb et al 2001;Torsvik et al 2001a,b;Pandit et al 2003;Buick et al 2010;Bhowmik et al 2010;Singh et al 2010;Chatterjee et al 2017;Tiwari & Biswal, 2019) plays an important role in the reconstruction of the Rodinia supercontinent (Dalziel, 1991;Hoffman, 1991;Moores, 1991;Li et al 1996Li et al , 2008Radhakrishna & Mathew, 1996;Torsvik et al 1996;Weil et al 1998;Mezger & Cosca, 1999;Torsvik et al 2001a,b;Powell & Pisarevsky, 2002;Kröner & Cordani, 2003;Pisarevsky et al 2003;Malone et al 2008;Gregory et al 2009). Studies from Aravalli Mobile Belt suggest a Grenvillian-age collisional orogen between the North Indian Block to the east and Marwar craton to the west (Deb et al 2001;Pandit et al 2003;Bhowmik et al 2010).…”

Aravalli Craton and its Mobile Belts: An Update

“…The age of massive sulfide ores in bimodal volcanics of Deri area dated at 1100 Ma falls in the same age bracket • The Rb-Sr age of 955 Ma to 740 Ma for the post-Delhi Pali-Sendra-Erinpura Magmatic Cycle is now well constrained with more precise zircon geochronology that also reflects the similar age bracket of 968±1.2 Ma to 800±2 Ma. Tiwari and Biswal (2019)…”