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Book Chapter

Organic Maturation Modeling Applied to Ore Genesis and Exploration

By
Andrew P. Giże
Andrew P. Giże
1
Department of Earth Sciences, University of Manchester
;
Oxford Road, Manchester M13 9PL United Kingdom
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C. A. Kuehn
C. A. Kuehn
2
IMDEX Inc.
,
P.O. Box 65538, Tucson, Arizona 85728
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K. P. Furlong
K. P. Furlong
3
Department of Geosciences, The Pennsylvania State University
,
University Park, Pennsylvania 16802
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J. M. Gaunt
J. M. Gaunt
4
Gold Fields Mining and Development
, P.O. Box
248, Warmbaths 0480, Republic of South Africa
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Published:
January 01, 1997

Abstract

One aspect of ore deposit studies is their potential application in prospecting for new deposits. That application has been considered in this volume (e.g., Leventhal and Giordano, 2000; Wood, 2000) and elsewhere. Heroux et al. (1996), for example, integrated organic reflectance and clay mineralogy to delineate alteration zones associated with mineralization. Both ore and petroleum deposits are a result of fluid migration, and from this viewpoint it can be expected that organic and inorganic fluids may use similar lithological pathways (Giże and Barnes, 1994). This chapter will briefly introduce organic maturation modeling as an approach to predicting both the age and relative timing of ore and petroleum fluids.

The thermal maturation of sedimentary organic matter is primarily a function of time and temperature. Simplistically, if two of the parameters (organic maturity, temperature, and time) are known, then the third can be derived. If organic maturity can be determined (using optical properties such as vitrinite or bitumen reflectance, or using geochemical parameters such as isomer ratios or elemental ratios), as well as temperature (fluid inclusions), then time (e.g., duration of heating event) can be estimated. A close association between organic matter and some ore deposits has been noted throughout this and other volumes. The association may reflect genetic links (e.g., reduction or complexing), or maysimply reflect genetically unrelated aqueous and hydrocarbon fluids using the same aquifer. Petroleum, or petroleum-derived bitumens, have been reported as inclusions in ore minerals from many ore deposits (Roedder, 1984). If the time-temperature dependence of organic matter can be used to estimate when the petroleum stage of organic maturation occurred, then a potential dating method for the age of the ore deposit is also established.

The use of organic modeling of the petroleum stage of organic maturation is shown for the Carlin (Nevada) disseminated gold deposit and the Bowland basin, United Kingdom, an historical district of renewed interest following the discovery of the Irish base metal deposits. The Carlin deposit provides an example of the use of organic modeling as a means of ascertaining whether or not organic matter was mobile at the time of mineralization, thus providing evidence to support or refute specific genetic concepts. The Bowland basin example will show that the integration of modeling, fluid inclusion data, and field observations can provide constraints on the probable age of mineralization.

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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

GeoRef

References

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