Large variation of Curie depth and lithospheric thickness beneath the Indian subcontinent and a case for magnetothermometry

Abstract

A first order estimate of Curie depth and lithospheric thickness variation beneath the Indian region has been obtained using the available geothermic data. The Curie depth is found to vary from 18 to 68 km and the lithospheric thickness from 38 to 186 km. These estimates conform well with the MAGSAT and seismological findings. Both the parameters exhibit covariancy and suggest the possibility of approximating heat flow values and lithospheric thickness in geothermally uncharted areas using Curie point geotherm depths derived from airlsatellite-borne magnetic anomalies. Interestingly, the areas with shallow Curie depth and lithospheric thickness are found to be associated with a thin crust, higher heat flow, higher geothermal gradients and positive gravity anomalies, and vice versa. Large thickness estimate of magnetic crustal layer, extending below the Moho, demands a new conceptual understanding. The study has brought out a good case for wider use of magneto-thermometry and provides understanding of the geodynamic evolution of the Indian subcontinent.

Simulated Annealing 2-D Nonlinear Inversion of Geomagnetic Deep Sounding Data Near Ujjain-Guna, India

“…8) passing over the conductor have been investigated. In the absence of crustal radioactivity information near the Ujjain-Guna region, lithospheric thickness and depth to the Curie-point isotherm have been estimated, based on the relationship given by NEGI et al (1987). The calculation suggests that this region has a relatively thick lithosphere of approximately 140 km and depth to the Curie-point isotherm at about 50 km.…”

Predicting heat flow in the 2001 Bhuj earthquake (<i>M</i><sub>w</sub>=7.7) region of Kachchh (Western India), using an inverse recurrence method

“…Further, observed surface heat flow has often been correlated with the thickness of the lithosphere Crough and Thompson, 1976;Negi et. al, 1987).…”

“…Based on mantle derived paleo-geotherms on these xenoliths, a minimum heat flow between 60 and 70 mW m −2 has been projected for this region by Mukherjee and Biswas (1988), following the method of calculation from Pollack and Chapman (1977). Similarly, empirical relationships given by Negi et al (1987) and Chapman and Pollack (1977) would also result in a surface heat flow of about 60 to 75 mW m −2 against a lithospheric thickness of 70 km, which is quite accurately known (Fig. 4).…”

“…In the past, it has been done using indirect methods like empirical relationship between heat flow and (i) lithospheric thickness (Negi et al, 1987;Chapman and Pollack, 1977), (ii) Pn velocity and seismic models of the crust and upper most mantle (Kubick,1988, Shapiro andRitzwoller, 2004), and (iii) regional geology (Chapman and Pollack, 1975;Sclater et al, 1980;Pollack et al, 1993;Davies and Davies, 2010). In the present paper, we first develop a methodology in the form of an inverse recurrence method to predict a first order surface heat flow for any particular region.…”

Geothermal Structure in a Seismoactive Region of Central India

“…It is observed that the Curie depth is non-uniform and may range from 6 to 40 km (SHUEY et al, 1977;LACHENBRUCH and SASS, 1977;MAYHEW, 1982). NEGI et al (1987), based upon the data from MAYHEW (1982) and Indian data, suggested that the heat flow decreases exponentially with an increase in Curie depth. However, the relationship between heat flow (Q) and Curie depth (H) can be better represented by the function with a correlation factor of 0.99 (Fig.…”