A new method to estimate the crustal and lithosphere thickness using elevation, geoid anomaly and heat flow

Abstract

We present a novel approach for joint inversion of heat flow, elevation and geoid anomalies which allows simultaneous determination of the deep thermal field as well as crustal and lithospheric structures. The technique is based on computationally stable iteration schemes and provide simultaneous checks for compatibility of the inversion results with the observational data on surface heat flow, radiogenic heat production, elevation and geoid anomalies. The results are found to be far more robust and realistic than those obtained in conventional thermal models. Unlike the previous attempts, the new approach incorporates surface heat flow variation as an independent constraining parameter and at the same time allow for the non-linear effects of thermal conductivity variation with temperature and in the crustal layers. The method was used in determining deep thermal structures of crustal blocks composing the São Francisco craton. The results obtained point to substantial variations in the crustal thickness; with mean values falling in the interval of 32 to 47 km. Such variations in crustal thickness are accompanied also by substantial intra-cratonic variations in the lithospheric thickness; with mean values extending over the the range of 90 – 210 km. These results are in reasonable agreement with values obtained in studies of seismic tomography.