Gravity and magnetic surveys were carried out in southwestern part of Cuddapah basin (CB) covering an area of ~3660 km2. Southwestern part of CB gained lot of attention after discovery of second most important uranium province in India. Some non-metallic industrial minerals and base metal occurrence are also reported in the study area. Present study with high spatial resolution gravity-magnetic survey aims to decipher detail basin geometry, nature of sediments, along with possible mineral deposits in SW part of CB. The gravity survey comprising short and long wavelength anomalies brought out sedimentary characteristics and basement architecture underneath the sediments. The long wavelength features of the gravity map shows gneissic basement, which is characterized by both basic and acid magmatic intrusive. Residual gravity anomaly map shows good correspondence with the exposed high density basaltic rock units and also brought out occurrence of concealed high density litho-units, which have significance for mineral prospecting. The magnetic map shows that both sediments and underneath basement are non-magnetic in nature except SW part of the study area, where study suggests occurrence of concealed mafic lensoid body. Euler solutions and combined gravity-magnetic modelling further facilitated for understanding of structural feature and basement geometry. Based on the integrated gravity and magnetic study mineral prospecting zones have been delineated for further detailed study.
The Palghat Cauvery Shear Zone (PCSZ), which dissects the Southern Granulite Terrane (SGT), evoked much attention for last two-three decades as it offers an enticing opportunity to understand Precambrian tectonics. Many studies suggest that it is a suture zone or a terrane boundary, but tectonic evolution is mainly derived from structural and geochronological evidences. The present gravity-magnetic study provides insight into both shallow and deeper crustal architecture and addresses the issues related to validation/modification of the existing tectonic realm. A total of 3,650 gravity and magnetic measurements were made covering 8,640 km 2 area, represented by high-grade metamorphic rocks and acid intrusives of Archean to Neoproterozoic age. Representative rock samples were also collected for determination of petrophysical properties (density and susceptibility) which have augmented the understanding of gravity-magnetic signature. The gravity anomaly map and subsequent modelling suggest an occurrence of a high-density batholith at mid-crustal level at the central part of the area. The magnetic anomaly map reveals that ENE-WSW trending linear magnetic low zone is coincident with a residual gravity high, which probably indicates the fossil of an oceanic crust. The horizontal gradient of gravity-magnetic data reveals the shallow crust, which is bounded by Palghat Cauvery Shear Zone (PCSZ) and Dharapuram Shear Zone (DSZ), and separates two terranes in terms of density and susceptibilities. The study suggests N-S verging compressional tectonics had led to closure of an ocean, imprints of which is well manifested in gravity and magnetic maps.
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