oa South African Journal of Geology - Connectivity between the western and eastern limbs of the Bushveld Complex

Volume 101 Number 4
  • ISSN : 1012-0750
  • E-ISSN: 1996-8590



The mafic layered rocks of the Bushveld Complex are 6 - 8 km thick and outcrop over an area of 65 000 km2. The mafic sequences in the western and eastern limbs are remarkably similar, which suggests that they formed within a single magma chamber. Yet previous interpretations of the Bouguer gravity anomalies negate the possibility that they could be connected at depth. These gravity models are inadequate as they do not consider the isostatic response of this huge mass of mafic rock on the crust. Isostatic readjustment caused the base of the crust to be depressed by up to 6 km. In terms of this model it becomes possible to construct a gravity profile, consistent with observed data, which includes a 6 - 8 km-thick sequence of mafic rocks a mere 11 km deep in the crust, connecting the western and eastern limbs of the Bushveld Complex, where there is no central positive gravity anomaly.

Die mafies gelaagde gesteentes van die Bosveldkompleks is 6 - 8 km dik en dagsoom oor 'n gebied van 65 000 km2 . Die mafiese opeenvolging in die westelike en oostelike flanke is opmerklik eenders, wat moontlik aandui dat hulle binne 'n enkele magma kamer gevorm het. Tog weerspreek vorige interpretasies van die Bouguer gravitasie-anomaliƫ die moontlikheid dat hulle in diepte verbind is. Hierdie gravitasie modelle is ontoereikend omdat hulle nie die isostatiese respons van hierdie groot massa mafiese gesteentes op die kors in ag neem nie. Isostatiese aanpassing het veroorsaak dat die basis van die kors tot 6 km afgedruk is. In terme van hierdie model word dit moontlik om in oorstemming met die waargenome data 'n gravitasieprofiel te konstrueer, wat 'n 6 - 8-km-dik opeenvolging van mafiese gesteentes insluit, skaars 11 km diep in die kors, wat die westelike en oostelike flanke van die Bosveldkompleks verbind, waar daar geen sentrale positiewe gravitasieanomalie is nie.

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