Electrical lithosphere beneath the Kaapvaal craton, southern Africa

Citations Over TimeTop 10% of 2011 papers

Abstract

[1] A regional-scale magnetotelluric (MT) experiment across the southern African Kaapvaal craton and surrounding terranes, called the Southern African Magnetotelluric Experiment (SAMTEX), has revealed complex structure in the lithospheric mantle. Large variations in maximum resistivity at depths to 200–250 km relate directly to age and tectonic provenance of surface structures. Within the central portions of the Kaapvaal craton are regions of resistive lithosphere about 230 km thick, in agreement with estimates from xenolith thermobarometry and seismic surface wave tomography, but thinner than inferred from seismic body wave tomography. The MT data are unable to discriminate between a completely dry or slightly “damp” (a few hundred parts per million of water) structure within the transitional region at the base of the lithosphere. However, the structure of the uppermost ∼150 km of lithosphere is consistent with enhanced, but still low, conductivities reported for hydrous olivine and orthopyroxene at levels of water reported for Kaapvaal xenoliths. The electrical lithosphere around the Kimberley and Premier diamond mines is thinner than the maximum craton thickness found between Kimberley and Johannesburg/Pretoria. The mantle beneath the Bushveld Complex is highly conducting at depths around 60 km. Possible explanations for these high conductivities include graphite or sulphide and/or iron metals associated with the Bushveld magmatic event. We suggest that one of these conductive phases (most likely melt-related sulphides) could electrically connect iron-rich garnets in a garnet-rich eclogitic composition associated with a relict subduction slab.

Related Papers

• → The Nico Pérez Terrane (Uruguay): From Archean crustal growth and connections with the Congo Craton to late Neoproterozoic accretion to the Río de la Plata Craton(2016)89 cited
• → Neoproterozoic tectonic structure of the Yenisei Ridge and formation of the western margin of the Siberian craton based on new geological, paleomagnetic, and geochronological data(2016)38 cited
• → Evolution of cratons through the ages: A time-dependent study(2019)21 cited
• → The Grenvillian Namaqua-Natal fold belt adjacent to the Kaapvaal Craton: 1. Distribution of Mesoproterozoic collisional terranes deduced from results of regional surveys and selected profiles in the western and southern parts of the fold belt(2014)16 cited
• → Imaging the electrical lithosphere of South Australia - 2D profiles and preliminary results of AusLAMP SA(2015)