This DFG funded project aims at imaging the electrical conductivity structure of the Barberton Greenstone Belt (BGB) in South Africa. The BGB is one of the few accessible parts of the Archean crust which comprises remnants of Early Earth tectonics. There is still a strong debate whether present day plate tectonic processes were active during the Early Archean or continental accretion was the result of predominantly vertical mass transport.

The Barberton Greenstone Belt (BGB) in South Africa provides a well-preserved natural laboratory to image the deep crustal structure of an Archean accretional terrane. Therefore, magnetotelluric (MT) experiments were conducted in April/May 2009 and July/August 2010 across the southern part of the BGB. This area is of particular interest since the southward continuation of the BGB and its main fault zones is unknown due to a sediment cover. The MT method in general allows resolving the electrical conductivity distribution at least down to lithospheric depths. The BGB is imaged as a highly resistive body sandwiched between more conductive geological units. Tectonic features such as faults and sutures within the BGB stand out as conductivity anomalies in 2D inversion models and are likely caused by mineralizations along shear planes. The approximately 200 MT sites give a good areal coverage and provide the data basis for extensive 2D and 3D analysis and interpretation.

Principal Investigators

• Ute Weckmann (GFZ)

Personnel

• Sissy Kütter (PhD) 2010
• Scott MacLennan (M.Sc.) 2011

Cooperations

• Maarten de Wit (NMMU Port Elizabeth, South Africa)

Methods & Equipment

              Magnetotellurics: 5-component measurements using

• Metronix induction coils MFS 05 and MFS 06
• Ag/AgCl electrodes
• SPAM Mk III
• CASTLE systems
• SPAM MK IV 

Publications/Results

• S. Kütter and U. Weckmann. 2012. Magnetotelluric measurements across the southern Barberton greenstone belt, South Africa: data improving strategies. Proceedings of the 24th Schmucker-Weidelt-Colloquium for Electromagnetic Depth Research, 146–152.

Ackowledgements

• DFG for funding the experiment (WE 2938/8-1), the Geophysical Instrument Pool Potsdam for providing the instruments, NRF and DST for their support, GFZ Potsdam for funding SK’s PhD research.

Additional Information

• Field work: 04/2009 – 05/2009 and 07/2010 – 08/2010