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• The northward extension of Godavari graben towards NSL revealed from both gravity and inverted Moho maps. • Heat flow map obtained from Curie depths shows higher heat flow below NSL and Godavari graben. • A complex high-density crust below NSL reveals imprint of multiple reworking along mobile belt/ fold belt. • The shallower DBMS compared DSS Moho depths below NSL reveals it as a thermal boundary. Narmada-Son Lineament (NSL) is a prominent geo-tectonic feature located in central India, characterised by complex geological structures and evolutionary history. In this study, we present a detailed joint interpretation of the aeromagnetic and gravity anomaly maps to delineate the crustal structure in order to address the thermo-tectonic activity below the NSL region. The ENE-WSW linear trend observed in the aeromagnetic anomaly map correlates well with the major tectonic elements of the NSL and the Vindhyan basin. The low-pass filtered regional gravity anomaly map and corresponding residual anomaly map revealed several crustal-scale structural features in the study area. The Curie depth map of the region prepared from the magnetic anomaly map shows the variation in depth between 24 and 48 km. The corresponding heat flow map correlates well with the trends in surface heat flow data. The gravity-derived Moho depth map reveals that the values vary between 30 and 59 km in the NSL region with deeper Moho below the Vindhyan basin. Further, the crustal models obtained from the constrained potential field modelling for two long transects across the NSL in the present study area revealed i) the absence of crustal underplating in the eastern part of NSL below Hirapur-Mandla region, ii) the presence of mid-crustal horst like structure below NSL, iii) undulating Moho with higher density crustal rocks within the NSL compared to the surrounding areas. The modelled crustal structure and the analysis of Curie depth as well as heat flow maps of the study area, reveal that the NSL region was affected by repeated tectonic activities since the Proterozoic times, and the present-day tectonics of this belt is greatly influenced by the reactivation of pre-existing faults along the NSL. [ABSTRACT FROM AUTHOR]

Abstract: The depth to the bottom of the magnetic sources (DBMS) has been estimated from the aeromagnetic data of Central India. The conventional centroid method of DBMS estimation assumes random uniform uncorrelated distribution of sources and to overcome this limitation a modified centroid method based on scaling distribution has been proposed. Shallower values of the DBMS are found for the south western region. The DBMS values are found as low as 22km in the south west Deccan trap covered regions and as deep as 43km in the Chhattisgarh Basin. In most of the places DBMS are much shallower than the Moho depth, earlier found from the seismic study and may be representing the thermal/compositional/petrological boundaries. The large variation in the DBMS indicates the complex nature of the Indian crust. [Copyright &y& Elsevier]

We estimated the Curie depth using magnetic anomalies in the tectonically complex central Indian shield. The modified centroid method for the scaling distribution of sources is applied to aeromagnetic data and satellite magnetic data (EMAG2) to estimate the Curie depths. We selected 80% overlapping with a window length of 300 × 300 km2 for Curie depth estimation. The estimated Curie depths are 22–46 km being shallower in the Bastar craton, northern end of the Aravalli-Delhi fold belt, and eastern part of Central Indian tectonic zone in the Deccan Volcanic Province. Deeper Curie depths are found in the eastern parts of the Aravalli-Delhi fold belt, Deccan Volcanic Province to the south of Tapti basin, parts of the Ganga and Vindhyan basins. The heat flow values estimated from the Curie depths vary from 30 to 90 mW/m2 being higher are in the northern part covering the Aravalli-Delhi fold belt and the Ganga basin and low heat flow values in the remaining study region. The computed thermal lithospheric thickness ranges 62–120 km, being 62 km thin in the Vindhyan basin, 68 km in the Aravalli-Delhi fold belt, and 73 km in the Bastar craton. We noticed a relatively thick thermal lithospheric thickness of 99 km beneath the foreland Ganga basin and 100 km in the Bundelkhand craton. The thermal lithosphere beneath the Deccan Volcanic Province is found to have a thickness ~ 120 km , which is interpreted as due to the rapid cooling of the lithosphere after Reúnion plume activity. Probably, the plume activities in the past could have modified the thermal lithospheric structure beneath central India. The upper mantle in the Deccan Volcanic Province to the south of the Tapti basin and the Aravalli-Delhi fold belt show magnetic character. • Curie depth (22–46 km), heat flow (30–90 mW/m2) are estimated using EMAG2 data. • Deep Curie depth in the DVP is an imprint of intense cooling after plume activity. • Heat flow is high in parts of the Bastar, Aravalli-Delhi fold belt, Vindhyan basin. • Upper mantle is magnetic in parts of Aravalli-Delhi fold belt, Vindhyan basin, DVP. • Thermal lithospheric thickness varies from 62 to 120 km beneath central India. [ABSTRACT FROM AUTHOR]

Abstract: This work deals with 2D thermal modeling in order to delineate the crustal thermal structure of central India along two Deep Seismic Sounding (DSS) profiles, namely Khajuriakalan–Pulgaon and Ujjan–Mahan, traversing the Narmada-Son-Lineament (NSL) in an almost north–south direction. Knowledge of the crustal structure and P-wave velocity distribution up to the Moho, obtained from DSS studies, has been used for the development of the thermal model. Numerical results reveal that the Moho temperature in this region of central India varies between 500 and 580°C. The estimated heat flow density value is found to vary between 46 and 49mW/m2. The Curie depth varies between 40 and 42km and is in close agreement with the Curie depth (40±4km) estimated from the analysis of MAGSAT data. Based on the present work and previous work, it is suggested that the major part of peninsular India consisting of the Wardha–Pranhita Godavari graben/basin, Bastar craton and the adjoining region of the Narmada Son Lineament between profiles I and III towards the north and northwest of the Bastar craton are characterized with a similar mantle heat flow density value equal to ∼23mW/m2. Variation in surface heat flow density values in these regions are caused by variation in the radioactive heat production and fluid circulation in the upper crustal layer. [Copyright &y& Elsevier]