Supergene enrichment

Lichtner, PC. and Biino, G.G. (1992) A first principles approach to supergene enrichment of a porphyry copper protoore. 1 Cu-Fe-S subsystem. Geochim. Cosmochim. Acta, 3987-4013. 

Supergene enrichment piayed a criticai roie in making northern Chiie the worid s prime copper-producing province. For copper porphyry deposits in the centrai... 

Reich, M., Palacios, C., Vargas, G., Luo, S., Cameron, E.M., Leybourne, M.I., Parada, M.A., Zuniga, A. 2009. Supergene enrichment of copper deposits since the onset of modern hyperaridity in the Atacama Desert, Chile. Mineralium Deposita, (in press). 

Hartley, A.J. Rice, C.M. 2005. Controls on supergene enrichment of porphyry copper deposits in the Central Andes A review and discussion. Mineralium Deposita, 40, 515-525. 

It is well known that the overwhelming majority of U deposits form as the result of two key processes - first endogenic (hypogene hydrothermal) and later supergene enrichment ones. We ll only view the processes of the former group. 

In contrast to the spatial restriction of marcasite to replacement of pyrrhotite, most covellite in mine wastes results from redeposition of solubilized copper that is typically derived from primary chalcopyrite. Sorption of copper on iron oxyhydr-oxides is common, but redeposition as a sulfide occurs where reductive conditions are present. Such conditions seem to be available locally on a micro scale in proximity to altering pyrrhotite, but on a broader scale the formation of covellite is predominant at the interface between the oxidized and reduced zones of a waste body, thus emulating the supergene enrichment process that takes place in sulfide deposits, especially those of porphyry copper. In mine wastes, other copper sulfides that resemble covellite in reflected light may also be present, but small grain size has impeded specific identification. 

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