G. Ramadass, K. Satish Kumar and G. Sri Ramulu
The present studies emphasize the significance of gravity anomalies in particular, the change in gradients of contours for understanding of geology and structural details. Regional Bouguer gravity anomaly map of Nalgonda district, Telangana State exhibits a range of 30 m Gal from a low of -75 m Gal to a maximum of -45 mGal, in the Eastern Dharwa craton to evaluate the structural configuration of the region, from qualitative analysis of, residual gravity, horizontal and analytical signal map brought out, eight conspicuous gravity lows (L1-L8), Nine gravity highs (H1-H9) and seven (F1 to F7) deep seated faults were identified. While the highs are attributed to basement undulations and/or the presence of basic rocks, dykes, the lows are attributed to variations in the peninsular gneissic complex. In addition, seventeen linear gravity trends, seven running NW-SE (L5, L6, L8, H3, H5, H7 & H8), three N-S (L3, L7 & H4 ), four trending in the NE-SW (L1, L2 ,H1, H6 & H7) and two E-W (L3 & H9) were delineated from qualitative analysis of Bouguer gravity data. Quantitative analysis from GM-SYS modeling inversion of eight profiles in the region brought out the subsurface layers configurations. The average depth of Peninsular gneissic layer varies from 8.25 to 11.66 Km, upper crustal layer ranging between 18.4 to 24.55 Km and bottom of the deeper crustal layer (Moho) is 34.35 to 37.45 Km The association of reported lamproites in the Vattikod, Ramadugu and Somavarigudem field with the subsurface topographic configuration of each of the layers taken separately as well as together was used to develop a plausible structural subsurface topographic criterion for their emplacement. The criterion for emplacement consist of margins of upwarps in the mantle combined with shallow occurrence of the peninsular gneissic basement in the region, and the zones of intersection of structural trends, resulting in circular to oval shaped structural features, which could have acted as potential sites for lamproites emplacement, four potential zones A-C are identified, as D zone merit for further detailed investigations
