Gravity and structural evidence for the deep structure of the limpopo belt, southern africa

Abstract

Gravity data have been used together with surface structural geology to examine the configuration of major shear zones and the position of high-grade gneisses beneath the Early Proterozoic Limpopo mobile belt of southern Africa. The structural and geophysical data demonstrate the asymmetry of the Limpopo belt with a suggested model of overthrusting of the Archaean Kaapvaal craton in South Africa over the Rhodesian craton, along a broad ductile shear zone which outcrops along the northern edge of the belt. The granulites at the northern edge of the belt have been uplifted by thrusting along this shear zone. Granulites at the southern margin of the belt may have been uplifted by shearing and faulting along the line of the Soutpansberg fault or they may have been upwarped due to the change in dip of the underlying shear zone. Amphibolites in the central part of the belt rest on a gently dipping shear zone which moved the southern part of the Limpopo belt to the west relative to the northern part. This movement is possibly much later than that which uplifted the granulites.