f Magnetotelluric Experiments Across The Southern Barberton Greenstone Belt, South Africa

The first formation of the crust is a controversially discussed topic amongst geoscientists. Tectonics on the Early Earth might have been similar to the plate movement and their driving forces that we observe today. However, regarding that some fundamental conditions like the thermal setting were considerably different at this time other processes like vertical mass transport might have played the governing role in tectonics. Unfortunately, there are only few remnants, e.g. the Barberton Greenstone Belt (BGB) in South Africa, where Early Earth’s tectonics can be studied. In the framework of the research initiative Inkaba yeAfrica two high resolution magnetotelluric (MT) field experiments were carried out in 2009 and 2010 across the southern part of the BGB. Unlike the surface structure which is well known from a number of geological studies, there is only little information on its deeper architecture. Imaging the complex subsurface is therefore the major aim of this project. The MT method allows resolving the electrical conductivity distribution at least down to lithospheric depths. Against the surrounding more conductive geological units the BGB is outlined as a highly resistive body. Mapping tectonic features within the BGB like faults and sutures which can be electrically conductive due to mineralizations along shear planes could be the first step to better understand the evolution of the BGB. However, various electromagnetic noise sources, e.g. power lines and electric fences, hinder the analysis of the MT data. Applying advanced filtering methods is therefore mandatory to improve the data quality as much as possible. Based on the good areal coverage of the ~ 200 MT sites (Figure 1), 2D interpretations along the six profiles with lengths between 80 and 110 km and a 3D analysis of the whole data set are conducted. In 2D models, the faults appear as zones of high conductivity down to a depth of 5 to 10 km; however, it seems difficult to follow these structures across neighbouring profiles. Therefore 3D inversion is more appropriate to correctly image this part of the Barberton Greenstone Belt.