Early to Mid‐Neoproterozoic Tectonics of Northwestern India and it’s implications for Rodinia reconstruction

The Phulad Shear Zone, a NE–SW trending ductile transpressional shear zone with a southeasterly dip, developed between ca. 820–810 Ma and marks the tectonic boundary between the Marwar Crustal Block and the South Delhi Fold Belt to the east. The evolution of the Marwar Crustal Block, particularly before its accretion to Greater India, is poorly understood but involves three phases of ductile deformation: D1, D2, and D3. The D1 deformation is restricted to enclave gneisses, while the Megacrystic granite was emplaced syn-tectonically during D2 deformation, forming NNW–SSE magmatic foliation oblique to the PSZ. D3 deformation coincides with the PSZ and includes the emplacement of the porphyritic Phulad granite (~820 Ma) along and across the shear zone. Field evidence indicates that the Phulad granite crystallized during the regional deformation associated with Phulad Shear Zone. Magmatic foliation in this Phulad granite is characterized by parallel alignment of feldspar phenocrysts and microgranitoid enclaves, transitioning to solid-state foliation due to ongoing deformation. Structural analyses reveal that releasing bends of N–S orientation within the Phulad Shear Zone provided the space for the granite’s emplacement under a transpressional regime. Geochronological data further constrain the tectonic history. U-Pb zircon ages in the Marwar Crustal Block document magmatic events at ~890 Ma and ~860 Ma, with monazite ages peaking at ~820 Ma, marking significant tectono-thermal activity. EPMA U-Pb-Th monazite and U-Pb LA-ICP-MS zircon ages from the Phulad granite confirm its magmatic age at ~819 Ma, supporting its role as a stitching pluton during the accretion of the Marwar Crustal Block with the Indian landmass Integrating structural, geochronological, and field data suggests that the accretion of the Marwar Crustal Block postdated ~860 Ma and culminated during ~820–810 Ma along the Phulad Shear Zone. This event marked the assembly of the Greater India landmass, with the Phulad Shear Zone acting as a significant suture zone. These findings highlight the distinct geological evolution of the Marwar Crustal Block and its role in the tectonic assembly of northwest India within the broader framework of Rodinia’s fragmentation and reassembly.