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Free keywords:
Inkaba yeAfrica Special Volume
DDC:
550 - Earth sciences
Abstract:
Two of the Earth´s largest geophysical anomalies, the Beattie Magnetic Anomaly (BMA) and the Southern Cape Conductive Belt (SCCB) extend across the southern African continent for more than 1000 km in an east-west direction. Based on previous electrical and magnetometer array measurements it is believed that both anomalies have a common crustal source with a width of 50 km represented by serpentinized palaeo-oceanic srust. New two-dimensional (2D) electrical conductivity models along a profile from Prince Albert to Fraserburg outline a narrow (2 km wide), southward-dipping zone of high electrical conductivity in the upper crust below the centre of the Beattie Magnetic Anomaly (BMA). Two-dimensional modeling studies of areo-magnetic data show that simple models that can explain the magnetic signature of the BMA, are not consistent with a narrow conductivity anomaly. Thus a common source for the two anomalies is unlikely. A second magnetotelluric (MT) experiment across the BMA, conducted along a 75 km profile centred on Jansenville, 350 km east of the first profile, resolves a sub-vertical and narrow condutivity anomaly below the centre of the BMA. At this location the conductor is reaching deeper to lower crustal levels and is inclined towards the north.
