Sulfide isotopic composition

Greenwood JP, Riciputi LR, McSween HY (1997) Sulfide isotopic compositions in shergottites and ALH 84001, and possible implications for life on Mars. Geochim Cosmochim Acta 61 4449 453... 

Figure 1.4]. Sulfur isotopic compositions of sulfide minerals from Kuroko deposits (Shikazono, 1987b).

Figure 1.109. Sulfur isotopic compositions of Neogene Au-Ag vein-type and disseminated-type deposits. Sulfur isotopic compositions on the samples from the Yatani deposits (Sample No. YT26 from Zn-Pb vein S S = -)-3.3%o), and HS72050305-YT1, YT24 and NS-3 from Au-Ag vein (average S S = +3.3%c)) by Shikazono and Shimazaki (1985) are also plotted. Base-metal rich implies the sample containing abundant sulfide minerals but no Ag-Au minerals from base-metal rich deposits and also from Ginguro-type deposits (Shikazono, 1987b).

Sulfur isotopic compositions (S S) of sulfides and sulfate (barite) from the Se-type and Te-type are summarized in Fig. 1.122. Almost all S S values from the Se-type and Te-type fall in a range from —3%o to - -6%o (Fig. 1.122). In general, the 5 S values from the Se-type are similar to those of the Te-type. However, some S S values from the Se-type are lower than those from the Te-type. 

This mechanism as a main cause for epithermal-type Au deposition is supported by sulfur isotopic data on sulfides. Shikazono and Shimazaki (1985) determined sulfur isotopic compositions of sulfide minerals from the Zn-Pb and Au-Ag veins of the Yatani deposits which occur in the Green tuff region. The values for Zn-Pb veins and Au-Ag veins are ca. +0.5%o to -f4.5%o and ca. -l-3%o to - -6%c, respectively (Fig. 1.126). This difference in of Zn-Pb veins and Au-Ag veins is difficult to explain by the equilibrium isotopic fractionation between aqueous reduced sulfur species and oxidized sulfur species at the site of ore deposition. The non-equilibrium rapid mixing of H2S-rich fluid (deep fluid) with SO -rich acid fluid (shallow fluid) is the most likely process for the cause of this difference (Fig. 1.127). This fluids mixing can also explain the higher oxidation state of Au-Ag ore fluid and lower oxidation state of Zn-Pb ore fluid. Deposition of gold occurs by this mechanism but not by oxidation of H2S-rich fluid. 

Figure 1.151. Sulfur isotopic compositions of sulfides in the vein-type and Kuroko deposits. Solid box represents sulfur isotopic data from the ore deposits occurring in basement rocks (Shikazono and Shimizu, 1993).

Kiyosu, Y. (1977a) Sulfur isotopic compositions of epithermal vein type sulfides from the Toyoha mine, Hokkaido, Japan. J. Earth Sci. Nagoya U., 22, 23-32. 

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. 

Shikazono, N. (1987b) Isotopic composition and origin of sulfide sulfur of Neogene Au-Ag and base metal vein-type deposits in Japan. U. Tokyo Fac. Sci. J. Sec., 21, 239-255. 

A large number of sulfur isotope data on the Besshi-type deposits are available, although the variation in individual deposit has not been studied well (Yamamoto et al., 1968, 1984a,b Kajiwara and Date, 1971 Miyake and Sasaki, 1980) (Fig. 2.52). The sulfur isotopic compositions of sulfides are different in different regions. 

Fig. 2.57. Pb isotopic compositions in volcanogenic Cu sulfide deposits in Japan. Diamond shape K], K2 and K3 indicate average values of Kuroko-type deposits Ki Taro (Cretaceous) K2 Northeast Japan (Miocene) K3 southwest Japan (Miocene). Note that the Shimokawa ores (solid square, Besshi subtype) and Yanahara ores (open square, Hitachi subtype), closely associated with sediments, tend to have slightly more radiogenic values than the others (solid circles) (Sato and Kase, 1996).

It is suggested that the mode of subduction of the Pacific Plate since the middle Miocene age related to Jackson s episode, hence oscillation of direction of lateral movement of Pacific plate. Synchronized igneous and hydrothermal activities and Jackson s episode indicate that the formations and characteristics of hydrothermal ore deposits (Kuroko and epithermal vein-type deposits) are largely influenced by plate tectonics (mode of subduction, direction of plate movement, etc.). For example, sulfur isotopic composition of sulfides is not controlled by /o and pH, but by of... 

It is important to distinguish clearly in this scenario between the general solidification of the Earth s crust, which had the effect of freezing in variations in the U/Pb and Th/Pb ratios, and the specific mineralization event which created the galena (lead sulfide, PbS) deposits, which removed the lead from the uranium and thorium, and effectively therefore froze the isotopic composition of the lead in the galena at the values representative of the time of mineralization. 

Virag A, Zinner E, Lewis RS, Tang M (1989) Isotopic compositions of H, C, and N in C8 diamonds from the Allende and Murray carbonaceous chondrites. Lunar Planet Sci XX 1158-1159 Volkening J, Papanastassiou DA (1989) Iron isotope anomalies. Astrophys J 347 L43-L46 Volkening J, Papanastassiou DA (1990) Zinc isotope anomalies. Astrophys J 358 L29-L32 Wadhwa M, Zinner EK, Crozaz G (1997) Manganese-chromium systematics in sulfides of unequilibrated enstatite chondrites. Meteorit Planet Sci 32 281-292... 

Vapor and brine from the Brandon vent of the East Pacific Rise have identical Fe isotope compositions, implying that phase separation does not produce an isotopic fractionation (Beard et al. 2003a). The role that sulfide precipitation plays in controlling the Fe isotope composition of the fluid remains unknown. The precision of the two sulfide analyses reported by Sharma et al. (2001) was not sufficient to resolve if sulfide precipitation would produce Fe isotope fractionation in the vent fluid. In a detailed study of sulfldes from the Lucky Strike hydrothermal field from the mid Atlantic Ridge, however, Rouxel et al. (2004) found that sulfldes span a range in 5 Fe values from -2.0 to +0.2%o, and that pyrite/marcasite has lower 5 Fe values ( l%o) as compared to chalcopyrite. The variations in mineralogy and isotope composition are inferred to represent open-system equilibrium fractionation of Fe whereby... 

Very few Zn isotope compositions have been produced on ores. Marechal (1998) (see also Marechal and Albarede 2000) analyzed a variety of Zn carbonates (smithsonite) and sulfides (sphalerite) from different localities in Europe. The maximum range of 8 Zn values is from -0.06 to +0.69%o with little apparent sulfide/carbonate fractionation (smithsonite may be up to 0.3%o heavier than associated sphalerite). Unpublished data (Table 1) from the Lyon group on sphalerite from the Cevennes, Southeastern France fall within this range and show that the 8 Zn values from a single mine such as Les Malines cluster within =4).2%o of each other. 

Figure 11.28 shows the rhenium and osmium isotopic compositions of black shales and sulfide ores from the Yukon Territory (Horan et al., 1994). The black shale and sulfide layers are approximately isochronous. The superimposed reference isochrons bracket the depositional age of the enclosing shales. One reference line represents the minimum age (367 Ma) with an initial ( Os/ Os)q ratio of one, consistent with the mantle isotopic composition at that age (see later). The other reference isochron is drawn for a maximum age of 380 Ma, with ( 870s/ 860s)o = 12 (the maximum value measured in terrigenous sediments). Further examples of application of Re-Os dating of sediments can be found in Ravizza and Turekian (1989). 

Another factor that is of great importance for the observed sulfur isotope variations of natural sulfides is whether sulfate reduction takes place in an open or closed system. An open system has an infinite reservoir of sulfate in which continuous removal from the source produces no detectable loss of material. Typical examples are the Black Sea and local oceanic deeps. In such cases, H2S is extremely depleted in " S while consumption and change in " S remain negligible for the sulfate. In a closed system, the preferential loss of the lighter isotope from the reservoir has a feedback on the isotopic composition of the unreacted source material. The changes in the " S-content of residual sulfate and of the H2S are modeled in Fig. 2.21, which shows that 5 S-values of the residual sulfate steadily increase with sulfate consumption (a linear relationship on the log-normal plot). The curve for the derivative H2S is parallel to the sulfate curve at a distance which depends on the magnitude of... 

The isotopic composition of present day ocean water is more or less constant with 5-values close to 0%c. The isotopic composition of ancient ocean water is less well constrained, but stiU should not be removed from 0 by more than 1 or 2%c. Many volcanogenic massive sulfide deposits are formed in submarine environments from heated oceanic waters. This concept gains support from the recently observed hydrothermal systems at ocean ridges, where measured isotopic compositions of fluids are only slightly modified relative to 0%c. 8 0 and 5D-values of vent fluids are best understood in terms of sea water interaction with the ocean crust (Shanks 2001). 

The isotopic composition of a hydrothermal sulfide is determined by a number of factors such as (1) isotopic composition of the hydrothermal fluid from which the mineral is deposited, (2) temperature of deposition, (3) chemical composition of the dissolved element species including pH and f02 at the time of mineralization, and (4) relative amount of the mineral deposited from the fluid. The first parameter is characteristic of the source of sulfur, the three others relate to the conditions of deposition. 

Fig. 3.34 S-isotope composition of (a) natural and (b) anthropogenic sulfur sources in the atmosphere, DMS Dimethyl-sulfide...

Palmer MR, Slack JF (1989) Boron isotopic composition of tourmaline from massive sulfide deposits and tourmalinites, Contr Miner Petrol 103 434 51 Palmer MR, Swihart GH (1996) Boron isotope geochemistry an overview. Rev Miner 33 709-744 Palmer MR, Spivack AJ, Edmond JM (1987) Temperature and pH controls over isotopic fractionation during the absorption of boron on marine clays, Geochim Cosmochim Acta 51 2319-2323 Palmer MR, London D, Morgan GB, Babb HA (1992) Experimental determination of fractionation of B/ °B between tourmaline and aqueous vapor a temperature- and pressure-dependent isotopic system, Chem Geol 101 123-129... 

---