Pyrite biogenic

Other sources of river sulfate Include natural biogenic emissions to atmosphere delivered to land in rain (3%), votanism (8%) and pyrite weathering (11 %). 

The5 " S vaiues for arsenopyrite and pyrite in Type ii veins might be iinked to the strataform VMS deposits of the BSC. in particuiar, the S S vaiues are simiiar to those for the Caribou Mine (iocated in the Caiifornia Lake Group [Spruce Lake Formation] above a feisic intrusion). The negative S S vaiue returned from one pyrite probabiy reflects biogenic S or reduced seawater suifate from the iapetus back-arc basin (Lentz etal. 1996). 

The microstructure in situ is often externally encrusted and internally filled with carbonates, pyrite or other mineral matter of apparently biogenic origin. 

Starting Materials. Pyrite isolated from the two kerogens constitutes approximately 2 wt % and has S S vaiues Qf +8.7 per mil. These values are enriched by 20-30 per mil compared to pyrite formed from near-surface biogenically reduced sulfate in porewaters of "normal" near-surface marine sediments (5). Bitumens extracted from the two samples contain 8.0 and 8.7 wt % organic sulfur with 5 4 vaiues 0f + 17.3 and +18.5 per mil respectively. Both pyrite free kerogens contained 10.3 wt % organic sulfur with isotope values of +15.9 per mil and +17.0 per mil respectively. 

Ohmoto H., Kakegawa T., and Lowe D. R. (1993) 3.4-billion-year-old biogenic pyrites from Barberton, South Africa sulfur isotope evidence. Science 262, 555—557. 

Carbonate and opaline-silica-rich sediments are exceptions to these generalizations. They are very low in detrital iron, because calcareous and siliceous skeletal debris is much lower in iron than terrigenous material. In these dominantly biogenic sediments, iron may become limiting the degree of pyritization is very high (>80%) and... 

Kohn M. J., Riciputi L. R., Stakes D., and Orange D. L. (1998) Sulfur isotope variability in biogenic pyrite reflections of heterogeneous bacterial colonization Am. Mineral 83(11-12 (Part 2)), 1454-1468. 

The Maastrichtian (latest Cretaceous) Israeli oil shales consist of four main groups of components organic matter biogenic calcite and apatite detrital clay minerals and quartz, with a little amount of authigenic pyrite and feldspar. The main chemical characteristics of the oil shales are reviewed,with an emphasis on those which may affect future utilization techniques. 

Studies of modern peat-forming environments have emphasized the importance of detrital influx (, syngenetic formation of pyrite (8) and biogenic silica (7,9), and in-situ mixing with underlying sediments (7,10) to account for mineral constituents in peat. Within... 

Many investigators have searched the mineral world for possible catalysts of biogenic reactions. Suggestive results have been obtained with metal ions, zinc for example (Lohrmann et al., 1980), clays (Cairns-Smith, 1982 Ferris, 1998), double-layer metal hydroxide minerals (Pitsch et al., 1995), pyrite (Wachtershauser, 1998), and iron-sulfur complexes (Cammack, 1983 Wachtershauser, 1998). To what extent such materials may have been crucial to the origin of life on earth is, however, not known. In addition, doubts have often been expressed that mineral catalysts could, alone, have sufficed to launch life. 

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