MINERALS/Sulphides 585 Table The major types of sulphide ore deposit Type Major minerals Metals extracted Examples po, pn, py, cpy, v po, pn, cpy Ni, Cu, Co, PGM Ni, Cu, PGM Sudbury, Ontario Merensky Reef, South Africa Tin and tungsten skarns Zinc lead skarns Copper skarns Porphyry copper/molybdenum py, py, py, py, Sn, W Zn, Pb Cu, Au Cu, Mo, Au Polymetallic veins py, cpy, gn, sph, ttd Cu, Pb, Zn, Ag Pine Creek, California, USA Ban Ban, Australia Carr Fork, Utah, USA Bingham Canyon, Utah, USA Climax, Colorado, USA Carnsell River, NWT py, cpy py, cpy, sph, gn Cu Cu, Pb, Zn Cyprus Japan Cu, Pb, Zn, Ag, Au Hg Creede, Colorado, USA Almaden, Spain py, cpy, gn, sph, ttd, asp, Cu, Pb, Zn, Ag, Au Japan py, uran, Au py, sph, gn py, sph, gn, cpy, asp ttd, po Au, U Zn, Pb, Cd Cu, Pb, Zn, Au, Ag Witwatersrand, South Africa Laisvall, Sweden Sullivan, British Columbia, Canada Tynagh, Ireland py, gn, sph Zn, Pb, Cd, Ga, Ge South eastern Missouri Ores related to mafic and ultramafic intrusions Sudbury nickel copper Merensky reef platinum Ores related to felsic intrusive rocks cass, sph, cpy, wolf sph, gn cpy cpy, bn, mbd Ores related to marine mafic extrusive rocks Cyprus type massive sulphides Besshi type massive sulphides Ores related to subaerial felsic to mafic extrusive rocks Creede type epithermal veins Almaden mercury type py, sph, gn, cpy, ttd, asp py, cinn Ores related to marine felsic to mafic extrusive rocks Kuroko type Ores in clastic sedimentary rocks Quartz pebble conglomerate gold uranium Sandstone hosted lead zinc Sedimentary exhalative lead zinc (Sedex) Ores in carbonate rocks Mississippi Valley type Abbreviation: po, pyrrhotite; pn, pentlandite; py, pyrite; cpy, chalcopyrite; v, violarite; cass, cassiterite; sph, sphalerite; wolf, wolframite; gn, galena; bn, bornite; mbd, molybdenite; ttd, tetrahedrite; asp, arsenopyrite; cinn, cinnabar; uran, uraninite; PGM, platinum group metals quartz monzonite Large masses of pyrite, sphalerite, galena, or chalcopyrite are also found in ore deposits formed by contact metamorphism (skarn deposits) Pyrite occurs, often as a major phase, in the majority of hydrothermal vein deposits and dominates the ore mineralogy of those deposits that might broadly be described as ‘volcanogenic’ These include the ores that occur in thick volcanic sequences, such as the Kuroko deposits of Japan In the so-called ‘black ore’ of Kuroko-type deposits, irregular masses of galena are intergrown on a fine scale with sphalerite, pyrite, and chalcopyrite In the Besshi-type deposits of Japan, the sulphides occur in dominantly sedimentary sequences and are again dominated by pyrite, chalcopyrite, sphalerite, and galena In sulphide ores in volcanosedimentary sequences that are associated with ophiolite complexes, as in the Troodos Complex deposits (Cyprus), pyrite and chalcopyrite dominate An understanding of the genesis of these deposits has rapidly developed in recent years through the observation of present-day volcanic and hydrothermal activity on the seafloor The disseminated to massive stratiform sulphide ores that occur, often conformably, within sedimentary sequences grade into the volcanogenic deposits discussed above Again, pyrite is the dominant ore mineral in these deposits, which include the Kupferschiefer-Marl Slate of northern Europe and the Copperbelt of Zambia and Zaire The latter contains not only a range of copper and copper–iron sulphides (chalcopyrite, bornite, chalcocite, covellite) but also significant amounts of cobalt in pyrite and the sulphospinel mineral carrollite In the context of sedimentary rocks, sulphides (galena and sphalerite with some pyrite) are major phases in many of the lead–zinc–barite–fluorite ores, which occur chiefly in limestones, and pyrite, along with the copper sulphides, occurs in the uranium– vanadium–copper ores that are associated with sandstones in areas such as the Colorado Plateau, USA In the gold–uranium ores that occur in conglomerates in the Witwatersrand, South Africa, and Elliot Lake, Ontario, Canada, pyrite is the major opaque phase As well as occurring as common accessory minerals in black shales, sulphides, especially pyrite and marcasite, are the major opaque mineral in coals The formation of sulphides in all of these environments is probably linked to the reaction of metals, particularly iron, released by the dissolution of detrital oxides and silicates, with sulphur produced by the bacterial reduction of sulphate present in interstitial waters This is observed in Holocene sediments, with pyrite (preceded by mackinawite and possibly greigite) forming through a diagenetic process occurring in the reduced