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Structural and geophysical transect across an archean suture
zone, Barberton Greenstone Belt
Scott MacLennan 1 , Ute Weckmann 2 , Oliver Ritter 3 Maarten De Wit 4
1. AEON, UCT, GFZ, South Africa, scottangusmac@gmail.com
2. GFZ, Germany, uweck@gfz-potsdam.de
3. GFZ, Germany, Oliver.Ritter@gfz-potsdam.de
4. AEON, UCT, South Africa, Maarten.dewit@uct.ac.za
ABSTRACT
In 2009 a magnetotelluric field campaign was carried out in the southern part of Barberton Greenstone Belt. The
profile was positioned at right angles to the NE-SW structural grain of the Greenstone Belt. While initial results
showed that there are vertical zones of high conductivity that correspond to major Archean shear zones, the data
quality was poor. A second field campaign August 2010 was conducted to collect more robust data.
Previously the southern extent of the Moodies- Inyoka fault system was investigated using structural techniques,
with a particular focus on the Stolzberg layered ultra mafic complex, which lies directly adjacent to the Moodies
fault. This serpentinised ultramafic complex has a complicated history and the less resistant serpentinite units have
many different generations of deformation. The serpentinites are now composed of many separate blocks, which
are separated by fault surfaces. These surfaces show a multitude of slickenfibres of different orientations. A series
of abandoned Asbestos mines within these serpentinites serves as an ideal location to study this deformation in
detail, owing to the excellent exposure. This analysis revealed that the deformation in this ultramafic unit was not
uniform, where the south western extent of the complex showed more strike slip motion, while in the north east
low to high angle reverse faults dominate. This change happens on the km scale. The data are not well constrained
though, showing low precision. This is attributed to the ease in which these serpentinites are deformed, creating
complex structural patterns.
Samples of major lithologies and rocks associated with shear zones from within the greenstone belt were collected
to test their electrical conductivity. This data will be used to constrain some of the modeling results from the
magnetotelluric survey and attempt to determine which material is responsible for the high conductivities observed
within these Archean suture zones.
KEYWORDS: archean, tectonics, magnetotellurics, serpentinites
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