Mapping the thermal structure of Southern Africa from wavelet transform and Bayesian inversion of magnetic data

Abstract:

Surface heat flow provides essential information on the thermal state and thickness of the lithosphere. Southern Africa comprises a mosaic of the best-preserved and exposed crustal blocks, which were assembled in early late Archean and subsequently modified by several major Precambrian and Phanerozoic tectono-thermal events.

Understanding the thermal and compositional structure of the southern African lithosphere provides crucial information for the actual causes, processes of lithospheric stability, and modification.

Temperature plays a major role in the distribution of the long-wavelength crustal magnetic anomalies. Curie depth offers a valuable constraint on the thermal structure of the lithosphere, based on its interpretation as the depth to 580°C.

Due to the sparse distribution of the surface heat flow, we examine the degree to which the thermal structure of the crust can be constrained from the Curie depth in Southern Africa. To understand the thermal evolution, we obtained the Curie depth from magnetic anomaly using wavelet analysis based on fractal magnetization in Southern Africa and then built a thermal model to estimate the heat flux distribution.

We quantify the uncertainty of Curie depth estimation within a Bayesian framework, where parameters relating to the thickness of magnetic sources are expressed in probabilistic terms.