Rajan Kumar^1*, Birendra Pratap², Naveen¹and Vijay Kumar Tyagi¹

¹Geophysics Division, Geological Survey of India, Central Region, Nagpur-440006(MS), India ²Department of Geophysics, Banaras Hindu University, Varanasi-221005(UP), India

(*Corresponding Author, E-mail: rajan.08.ism@gmail.com)

Abstract

The article is the highlights of the mapping of crustal structures such as inferred fault/lineament, tectonic contacts and basin boundaries using potential field method (Gravity and Magnetic methods) in parts of Raipur, Janjgiri-Champa, Mahasamund and Raigrah districts, Central Chhattisgarh, Central India. Geologically, the area of investigation is comprised by Tonidongar Bengpal, Bengpal Gneiss, Sukma, Sonakhan, Singhora, Chandarpur, and Raipur Group. Several filtering and processing techniques are applied on potential field anomalies (Bouguer gravity and Magnetic) for outlining of crustal structures, which in turn correlated well with the geological features. The general trend of gravity and magnetic contour is in NW-SE direction which is in good correlation with NW-SE alignment of geological formations. The high gravity (H1) values (-26.5 to -8.9mGal) recorded near Sonakhan and Deori villages which align in NW-SE direction is due to Meta Basalt (high density formation) in Sonakhan Formation. The gravity ‘high’ (H2) values observed near Deori and Harda is due the cumulative effect of Metabasalt, Meta Gabbro, Phyllite and, Meta Rhyolite of Sonakhan Formation. The gravity ‘low’ (L2) values (-62.4 to -50.1mGal) is observed near Katgi and Pauni in western part which may be due to Hirri Sub-basin within Chhattisgarh Basin with deeper basement. The major gravity gradient (F3-F3′) is trending in E-Wand NW-SE direction near Katgi, Pauni and Sonakhan villages is demarcated as the boundary of Hirri Sub-basin within Chhattisgarh Basin. The low intensity magnetic (T.F.) anomalies (-628.00 to 19.77nT) are reflected near Sankara, eastern part of Pithora and southern part of Nanwapara due to the presence of Quartzite and Granite gneiss. The general regional trend of regional gravity contour is in NW-SE directions. Gravity highs (H1, H2 and H3) still exist in the regional gravity map indicating that causative sources of these anomalies are from deeper level. The Regional magnetic anomaly map provides integrated view of the study area with smooth trend. The prominent shallow features near Sonakhan-Deori and Deori-Harda villages are due to presence of Meta Basalt (high density formation) and cumulative effect of formation such as Meta basalt, Phyllite and Meta Rhyolite of the Sonakhan Formation. The Vertical derivative low near Katgi and Pauni, in the central part is observed over sub-basin (Hirri Sub-basin) of Chhattisgarh Formation due to the deeper basement. The Euler depth solutions are provided less than 1.5Km, 1.5 to 3.0Km, 3.0 to 5.0Km and beyond 5.0Km of gravity data. The solution of gravity data is falling at inferred lineament and contact between two litho-units varying depth from 1.5 to 5.0Km.

Keywords: Mapping, Crustal Structure, Gravity and Magnetic Methods, Central Chhattisgarh