Factors controlling the precipitation of copper and cobalt minerals in sediment-hosted ore deposits: Advances and restrictions
详细信息 查看全文
- 作者：Ph. Mucheza ; philippe.muchez@ees.kuleuven.be ; M. Corbellab ; merce.corbella@uab.es
- 关键词：Central African Copperbelt ; Cobalt sulphides ; Copper sulphides ; Reactive transport modelling ; Sediment-hosted stratiform deposits
- 刊名：Journal of Geochemical Exploration
- 出版年：2012
- 出版时间：July, 2012
- 年：2012
- 卷：118
- 期：Complete
- 页码：38-46
- 全文大小：910 K
文摘
An assessment is presented of existing data on the most important copper and cobalt complexes and sulphides applied to reactive transport modelling. The most important complexes in ore-forming hydrothermal solutions at 150 ¡ãC are CoCl(H2O)5+, CoCl4?#xA0;2 and CoCl2(H2O)2(aq) for cobalt, and CuCl2?/sup> and CuCl3?#xA0;2 for copper. Reactive transport modelling was carried out to simulate the transport and precipitation of copper and cobalt sulphides in sediment-hosted stratiform ore deposits, such as the Central African Copperbelt. A limitation is the lack of thermodynamic data for carrollite (CuCo2S4). Initially chalcopyrite (CuFeS2) and cattierite (CoS2) precipitate in a reducing host rock. Pyrite dissolves in the horizon where both minerals form and it precipitates in adjacent rocks. The continuous supply of copper and cobalt causes formation of the metal-rich sulphides bornite (Cu5FeS4) and linnaeite (Co3S4). Chalcopyrite and cattierite precipitate further in the flow direction. In this model, the dissociation reaction of chalcopyrite and bornite are:
CuFeS2(s) + 2 H+ = Cu2+ + Fe2+ + 2HS?/sup> Cu5FeS4(s) + 2 H+ = 4Cu+ + Cu2+ + Fe2+ + 4HS?/sup> However, if the dissociation reactions only include Cu+ and Fe3+, simulations show the precipitation of only chalcocite (Cu2S), which is explained by the low concentration of trivalent iron in solution. The dissociation reactions are: CuFeS2(s) + 2 H+ = Cu+ + Fe3+ + 2HS?/sup> Cu5FeS4(s) + 2 H+ = 5Cu+ + Fe3+ + 4HS?/sup>