Imaging the Kheis Terrane Crustal Structures: an integrated magnetotelluric - seismic - magnetic - geological study

Abstract

The Kheis Province and Kaaien Terrane in the Northern Cape have challenges in understanding their substructure due to the complex subsurface and limited geophysical imaging. Recent studies advocate for revising their classification and merging them into the Kheis Terrane, yet detailed geological mapping has been insufficient to reach a consensus. Addressing this, my study employs 3D magnetotelluric (MT) inversion modelling and seismic-MT cross-sections to attempt to enhance understanding the Kheis Terrane. The MT data analysis reveals electrical anisotropy and structural complexity in the subsurface, supported by apparent resistivity plots and phase diagrams. Penetration depth analysis indicates variations in subsurface resistivity up to 200 km below the surface, with phase tensor maps showing predominantly NW-SE oriented 2-D structures. 3D inversion modelling provides insights into resistive and conductive zones, validated by integration with seismic and magnetic data. The proposed geological model confirms the Kheis Terrane's boundaries and supports the 'Kheis Event' theory, suggesting a tectonic collision between the Namaqua-Natal Metamorphic Province and the Kaapvaal Craton. This study suggests that the Kheis Terrane is interlocked with the craton and extends approximately 20 km deep. This comprehensive approach enhances our understanding of the region's geological evolution and provides valuable insights for further research.