3 July, 2009 (16:00 GMT), 5 Merrion Square, Dublin 2.

Speaker: David Khoza (DIAS).
Title: Magneto-telluric imaging across a Neoproterozoic collision zone: Damara belt and surrounding cratonic blocks.

Abstract:

The Southern African Magnetotelluric Experiment (SAMTEX) is the largest ever land-based magnetotelluric (MT) project. The main objective of the project is to define the geo-electric structure across the region in order to gain a better understanding of Archean and Proterozoic tectonic processes. The Damara belt in northern Namibia forms part of a highly complex orogenic system that records the closure of an in-land sea and the late Neoproterozoic collisional event between the Congo and Kalahari cratons. This collision event was followed by protracted Pan African (circa 650-550 Ma) tectono-thermal events that included episodic granite emplacements, metamorphism and structural deformation. MT profiles crossing the Rehoboth Terrane, the Neoproterozoic Ghanzi-Chobe/Damara belts (collectively termed the DMB) and the southern Angola craton are the focus of this study. This study is aimed specifically to increase our understanding of the juxtaposition of these tectonic blocks (i.e. Rehoboth Terrane, Angola craton and the DMB) and to infer the nature and geometry of these boundaries at depth. An analysis of structural directions and dimensionality indicates significant depth and lateral variations in geo-electric strike direction and dimensionality on all transects crossing these three tectonic units . Preliminary 2D inversion models indicate lateral variations in the crustal resistivity structure. The approximate boundary of the Damara belt in relation to both the Angola and Rehoboth terranes is evident as a steeply dipping, highly conductive structure and can be correlated with the regional magnetic results.