Sulfide deposits

Fig. 2. Distribution of ( ) known and (o) suspected metalliferous sulfide deposits and active hydrothermal vents in the Pacific Ocean (42).

Deposits which are forming are frequentiy characterized by venting streams of hot (300°C) mineralized fluid known as smokers. These result in the local formation of metalliferous mud, rock chimneys, or mounds rich in sulfides. In the upper fractured zone or deep in the rock mass beneath the vents, vein or massive sulfide deposits may be formed by the ckculating fluids and preserved as the cmstal plates move across the oceans. These off-axis deposits are potentially the most significant resources of hydrothermal deposits, even though none has yet been located. 

Deposits. Selenium forms natural compounds with 16 other elements. It is a main constituent of 39 mineral species and a minor component of 37 others, chiefly sulfides. The minerals are finely disseminated and do not form a selenium ore. Because there are no deposits that can be worked for selenium recovery alone, there are no mine reserves. Nevertheless, the 1995 world reserves, chiefly in nonferrous metals sulfide deposits, are ca 70,000 metric tons and total resources are ca 130,000 t (24). The principal resources of the world are in the base metal sulfide deposits that are mined primarily for copper, zinc, nickel, and silver, and to a lesser extent, lead and mercury, where selenium recovery is secondary. 

Some of the most important metal sulfides are pyrite [1309-36-0] EeS2 chalcopyrite [1308-56-1J, CuEeS2 pyrrhotite [1310-50-5] Ee sphalerite [12169-28-7] ZnS galena [12179-39-4] PbS arsenopyrite [1303-18-0] 2 pentlandite [53809-86-2] (Fe,Ni)2Sg. Sulfide deposits often occur in... 

Like selenium, tellurium minerals, although widely disseminated, do not form ore bodies. Hence, there are no deposits that can be mined for tellurium alone, and there are no formally stated reserves. Large resources however, are present in the base-metal sulfide deposits mined for copper, nickel, gold, silver, and lead, where the recovery of tellurium, like that of selenium, is incidental. 

Copper ore minerals maybe classified as primary, secondary, oxidized, and native copper. Primaryrninerals were concentrated in ore bodies by hydrothermal processes secondary minerals formed when copper sulfide deposits exposed at the surface were leached by weathering and groundwater, and the copper reprecipitated near the water table (see Metallurgy, extractive). The important copper minerals are Hsted in Table 1. Of the sulfide ores, bornite, chalcopyrite, and tetrahedrite—teimantite are primary minerals and coveUite, chalcocite, and digenite are more commonly secondary minerals. The oxide minerals, such as chrysocoUa, malachite, and azurite, were formed by oxidation of surface sulfides. Native copper is usually found in the oxidized zone. However, the principal native copper deposits in Michigan are considered primary (5). 

Most copper deposits are (/) porphyry deposits and vein replacement deposits, (2) strata-bound deposits in sedimentary rocks, (J) massive sulfide deposits in volcanic rocks, (4) magmatic segregates associated with nickel in mafic intmsives, or (5) native copper, typified by the lava-associated deposits of the Keweenaw Peninsula, Michigan. 

Figure 4.20 Sulfide deposits (dark patches) on longitudinally split brass heat exchanger tube. Note the perforation where wastsige penetrated the tube wall. Sulfide was spalled after perforation by escaping fluids.

A relatively high degree of corrosion arises from microbial reduction of sulfates in anaerobic soils [20]. Here an anodic partial reaction is stimulated and the formation of electrically conductive iron sulfide deposits also favors the cathodic partial reaction. 

Solid catalysts for the metathesis reaction are mainly transition metal oxides, carbonyls, or sulfides deposited on high surface area supports (oxides and phosphates). After activation, a wide variety of solid catalysts is effective, for the metathesis of alkenes. Table I (1, 34 38) gives a survey of the more efficient catalysts which have been reported to convert propene into ethene and linear butenes. The most active ones contain rhenium, molybdenum, or tungsten. An outstanding catalyst is rhenium oxide on alumina, which is active under very mild conditions, viz. room temperature and atmospheric pressure, yielding exclusively the primary metathesis products. 

In situ metallization has been claimed to provide a convenient method for the preparation of metal-deposited and metal sulfide deposited CdS during photocatalytic decomposition of aqueous sulfide. As-prepared MS/CdS and M/CdS bifunctional photocatalysts (MS = Pt or Ir sulfide M = Pt or Ir) were reported to be more active photocatalysts than CdS and ex-situ metallized CdS [285]. 

Rufus IB, Viswanathan B, Ramakrishnan V, Kuriacose JC (1995) Cadmium sulfide with iridium sulfide and platinum sulfide deposits as a photocatalyst for the decomposition of aqueous sulfide. J Photochem Photobiol A 91 63-66... 

DISTRIBUTION OF KUROKO-TYPE MASSIVE SULFIDE DEPOSITS IN JAPAN... 

Figure 1.10. The distribution of the Green Tuff belt of Japan and the Kuroko-type massive sulfide deposits within it. Major mining districts are labeled and ore deposit clusters outlined (Cathles, 1983a).

Positive Eu anomaly is observed for hydrothermal solution issuing from the hydrothermal vent on the seawater at East Pacific Rise (Bence, 1983 Michard et al., 1983 Michard and AlbarMe, 1986). Guichard et al. (1979) have shown that the continental hydrothermal barites have a positive Eu anomaly, indicating a relatively reduced environment. Graf (1977) has shown that massive sulfide deposits and associated rocks from the Bathurst-Newcastle district. New Brunswick have positive Eu anomalies. These data are compatible with positive Eu anomaly of altered basaltic rocks, ferruginous chert and Kuroko ores in Kuroko mine area having positive Eu anomaly and strongly support that Eu is present as divalent state in hydrothermal solution responsible for the hydrothermal alteration and Kuroko mineralization. 

The above mechanism (boiling, loss of CO2 and increase in pH) could also lead to the deposition of other sulfides. The reactions causing sulfide depositions by this mechanism are written as. 

The plot of K2O versus Si02 for volcanic rocks thought to be genetically related to Au mineralization indicates that high sulfidation deposits (hot spring-type deposits appear... 

Cathles, L.M. (1983a) Kuroko-type massive sulfide deposits of Japan Products of an aborted Island-arc rift. Econ. GeoL Mon., 5, 96-114. 

Converse, D.R., Holland, H.D. and Edmond, J.M. (1984) Flow rates in the axis hot springs on the East Pacific Rise (21°N) Implications for the heat budget and the formation of massive sulfide deposits. Earth Planet. Sci. Lett., 69, 159-175. 

Graf, J.L. Jr. (1977) Rare earth element as hydrothermal tracers during the formation of massive sulfide deposits in volcanic rocks. Econ. Geoi, 72, 527-548. 

Halbach, P., Nakamura, K., Wahsner, M., Lange, J., Sakai, H., Kaselitz, L., Hansen, R.-D., Yamano, M., Post, J., Prause, B., Seifent, R., Michaelis, W., Teichmann, R, Kinoshita, M., Marten, A., Ishibashi, J., Czerwinski, S. and Blum, N. (1989) Probable modern analogue of Kuroko type massive sulfide deposits in the Okinawa Trough back-arc basin. Nature, 333, 496-499. 

Janecky, D.R. and Seyfried, W.E. Jr. (1984) Formation of massive sulfide deposits on oceanic ridge crests incremental reaction models for mixing between hydrothermal solutions and seawater. Geochint. Cosmochim. Acta, 48, 2723-2738. 

Kajiwara, Y. and Date, J. (1971) Sulfur isotope study of Kuroko type and Kieslager type stratabound massive sulfide deposits in Japan. Geochem. J., 5, 133-150. 

Kiyosu, Y. (1977b) Sulfur isotope ratios of ores and chemical environment of ore deposition in the Taishu Pb-Zn sulfide deposits, Japan. Geochem. J., 11, 91-99. 

Nysten, P. (1986) Gold in the volcanogenic mercury-rich sulfide deposit LSngsele, Skellefte ore district, northern Sweden. Mineralium Deposita, 21, 116-120. 

Ohmoto, H. and Skinner, B.J. (eds.) (1983) The Kuroko and Related Volcanogenic Massive Sulfide Deposits. Econ. Geol Mon., 5, 604 pp. 

Pisutha-Amond, V. and Ohmoto, H. (1983) Thermal history and chemical and isotopic compositions of the ore-forming fluids responsible for the Kuroko massive sulfide deposits in the Hokuroku district of Japan. Econ. Geol. Mon., 5, 523-558. 

Urabe, T., Scott, S.D. and Hattori, K. (1983) A comparison of footwall-rock alteration and geothermal systems beneath some Japanese and Canadian volcanogenic massive sulfide deposits. Econ. Geol. Mon., 5, 345-364. 

Whitford, D.J., Korsch, M.J., Orritt, PM. and Craven, S.J. (1988) Rare-earth element mobility around the volcanogenic polymetallic massive sulfide deposit at Que River, Tasmania, Australia. Chem. Geol, 8, 105-112,... 

Average content (in parts per million or wt%) of selected metals in samples from the Sunrise deposit compared with other modem seafloor deposits and an average Kuroko massive sulfide deposit (lizasa et ah, 1999)... 

Average bulk compositions of samples from seafloor sulfide deposits at seamounts and back-arcs (Scott, 1997)... 

Chemical composition of selected mineral assemblages from midocean ridge sulfide deposits (Hannington et al.. 1995). N number of analyses... 

Midoceanic ridge deposits are divided into volcanic-type and sedimentary-type (Gamo, 1995) or sediment-starved type or sediment-covered type (Scott, 1997). Metals concentrated to two types are distinct. In the sulfide deposits at Escanaba Trough,... 

Paleozoic-Mesozoic volcanogenic stratiform Cu deposits in Japan which are generally metamorphosed have been called Besshi-type deposits (Kato, 1937) or bedded cupriferous iron sulfide deposits (Kanehira and Tatsumi, 1970). 

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