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- Some aspects of the stratiform ore deposits of the Zambian Copperbelt and their genetic significance
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Some aspects of the stratiform ore deposits of the Zambian Copperbelt and their genetic significance
Abstract
In recent years the concept of synsedimentary precipitation of copper-iron-(cobalt) sulphides for the stratiform deposits of the Zambian Copperbelt has become widely accepted by many Zambian based mine Geologists and others who have studied these deposits. However, recent work by the author has led him to hold very grave doubts on the ability of this theory to satisfactorily explain the facts.
Though the presence of anhydrite in the potentially mineralized horizons of the Lower Roan Group has long been recognized, and has been used as an environmental indicator, its significance as far as ore genesis is concerned has apparently been missed. Whether the ore bearing host rock be arenite, argillite or siltstone, an antipathetic relationship can be demonstrated between copper and/or iron sulphides on the one hand, and anhydrite on the other. Evidence is presented which indicates that some, if not all, of the sulphides formed at the expense of anhydrite, whether this mineral was originally in nodular form or occurred as an interstitial cement.
A geologic model is proposed to explain the genesis and localization of the Copperbelt mineralization. This model, which bears close similarities with those proposed for Mississippi Valley type deposits, is based on the diagenetic evolution of depositional basins containing both carbonaceous and sabkha facies.
Other factors, such as the distribution of cobalt, and the tectonic evolution of the present structural basins, are examined and their genetic implications discussed.
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About: A.E. Annels
Department of Mineral Exploitation, University College, Newport Road, Cardiff CF 2, ITA, U.K.