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Book Chapter

The Nature and Roles of Organic Matter Associated with Ores and Ore-Forming Systems: An Introduction

By
Joel S. Leventhal
Joel S. Leventhal
U.S. Geological Survey
,
Box 25046, MS 973, Federal Center, Denver, Colorado 80225
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Thomas H. Giordano
Thomas H. Giordano
Department of Geological Sciences, New Mexico State University
,
MSC 3AB, P.O. Box 30001, Las Cruces, New Mexico 88003
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Published:
January 01, 1997

Abstract

The association of organic matter with ore minerals, gangue, and host rock in many low-temperature (<120°C) to moderate-temperature (120°-350°C) ore deposits is a well-known phenomenon (Saxby, 1976; Leventhal, 1986; Parnell et al., 1993; Giordano, 1996; Giże, 1999) and was recognized early in the twentieth century (Siebenthal, 1915; Harder, 1919; Schneiderholm, 1923; Bastin, 1926; Fowler, 1933). The study of organic constituents in ores, particularly if coupled with studies of other ore components and conditions, can provide much information on both active and passive roles of organic matter before, during, and after ore genesis, and in some cases can lead to the development of valuable exploration techniques.

By the 1950s, it was recognized that biological sequestering of metals, sulfide production by sulfate-reducing bacteria, biological precipitation of metals, sorption of metals by organic colloidal particles, modification of geochemical environments by organic processes, and the mobilization of metals by metal-organic complexes were all potentially important roles played by organic matter in the concentration of metals to form metalliferous shales and certain types of ore deposits (Berger, 1950; Krauskopf, 1955). By the 1960s, it was recognized that dead organic matter (organic matter not in living organisms) may be a powerful reducing agent for sulfate and thus may provide a source of sulfide for ore-forming systems (Barton, 1967; Skinner, 1967). Roedder (1967) reported the presence of hydrocarbons and sulfate in fluid inclusions from ore deposits. This observation was cited by Barton (1967) as strong evidence that organic matter was present at the time of ore formation and that thermodynamic equilibrium (which predicts hydrogen sulfide and carbon dioxide) was not attained in the ore fluid because of sluggish kinetics at the low temperature of ore formation. Hoering (1967) summarized his pioneering work on organic matter associated with gold and uranium in the Carbon Leader Formation of the Witwatersrand district, South Africa. Because it was relatively immature Precambrian organic matter (rather than graphite), it was suitable for analysis of simple and complex chemical compounds and led the way for future studies of organic matter in ore deposits and Precambrian rocks (Leventhal et al., 1975).

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Contents

Reviews in Economic Geology

Ore Genesis and Exploration: The Roles of Organic Matter

Society of Economic Geologists
Volume
9
ISBN electronic:
9781629490168
Publication date:
January 01, 1997

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