MAGNETIC FABRIC IN THE UMVIMEELA DYKE, SATELLITE OF THE GREAT-DYKE, ZIMBABWE

Anisotropy of magnetic susceptibility (AMS) has been determined for 22 locations from the 500-km-long gabbroic Umvimeela Dyke of Zimbabwe. AMS is controlled by the presence of multi-domain magnetite grains which appear to have preserved a variety of magnetic fabrics related to magma movement at the time of dike emplacement. Three locations along the Umvimeela Dyke have been identified as feeder points at which magma flowed into the dike from below. Lateral flow away from these points supplied the rest of the dike system. The presence of several foci of igneous activity along the Umvimeela Dyke parallels the development of the neighbouring contemporaneous Great Dyke layered complex, which consists of a line of contiguous subchambers. Individual feeder points to the Umvimeela Dyke may be directly related to activity in adjacent subchambers.