Comprehensive Gravity, Magnetic and Radiometric Analysis of the Eastern Ghat Mobile Belt–Cuddapah Basin Collision Zone: New Insights on Concealed Structures, Felsic Magmatism and Tectonic Dynamics

ABSTRACT The study aims to delineate the small intrusive bodies, intrusive zones, shear related sympathetic structures and add inputs in tectonic history at the contact zone of tectonically contrasting geological terranes, i.e., the Nallamallai group of Cuddapah Basin (CB), Nellore Schist Belt (NSB) and Eastern Ghats Mobile Belt (EGMB), which are not evident in earlier regional scale studies. Detailed gravity, total field magnetic and radiometric surveys at station spacing of 500 m were collected over 700 km 2 area with 1486 stations. The Bouguer gravity anomaly and total‐field magnetic anomaly map intuitively delimits the contacts between these three geological terranes. Bouguer gravity anomaly reveal NE–SW trending weak zones that host low‐density granitic intrusions and denser gabbroic–dolomitic bodies, while total field magnetic data clearly delineate the CB–NSB–EGMB boundaries, major shear zones and localized high‐susceptibility BIF and mafic intrusive bodies in the studied area. Residual Bouguer gravity anomaly, radiometric total‐count and ternary data delineate younger granites, nepheline syenites, their subsurface extensions and uranium‐rich zones in the Vellikonda Shear Zone (VSZ). The results reveal that the VSZ and sympathetic structures in the EGMB extend from 0.5 to 3 km with eastward‐dipping geometries, consistent with oblique thrust and transpressional tectonics. Granitic intrusions occur at depths of 2 to 5 km, while relict NSB patches are observed at 1 to 3 km. Shallow intrusive roots along the VSZ range from 0.5 to 1 km, with maximum crustal involvement reaching approximately 5.13 km, highlighting emplacement along pre‐existing structural weaknesses and progressive shearing and faulting. Joint 2D gravity‐magnetic modelling and 3D density inversion are employed to delineate the subsurface geometry of intrusive bodies and the depth‐dependent dip variations of major shear zones across the EGMB. The conceptual geological model provides a detailed tectonic perspective, emphasizing the imprint of younger tectono‐thermal events on the pre‐existing crustal architecture. The findings suggest that low‐density intrusions are emplaced along shear‐related sympathetic structures, serving as pathways for both younger felsic plutons and mineral‐enriched hydrothermal fluids within a complex tectonic architecture of continental collision and accretion.