Geological characteristics of epithermal precious and base metal deposits

Simmons, Stuart F., White, Noel C. and John, David A. (2005). Geological characteristics of epithermal precious and base metal deposits. In Jeffrey W. Hedenquist, John F. H. Thompson, Richard J. Goldfarb and Jeremy P. Richards (Ed.), Economic Geology One Hundredth Anniversary Volume: 1905-2005 (pp. 485-522) Littleton, CO, U.S.A.: Society of Economic Geologists.

Author Simmons, Stuart F.
White, Noel C.
John, David A.
Title of chapter Geological characteristics of epithermal precious and base metal deposits
Title of book Economic Geology One Hundredth Anniversary Volume: 1905-2005
Place of Publication Littleton, CO, U.S.A.
Publisher Society of Economic Geologists
Publication Year 2005
Sub-type Critical review of research, literature review, critical commentary
ISBN 9781887483018
1887483012
Editor Jeffrey W. Hedenquist
John F. H. Thompson
Richard J. Goldfarb
Jeremy P. Richards
Chapter number 15
Start page 485
End page 522
Total pages 38
Total chapters 56
Language eng
Subjects 040307 Ore Deposit Petrology
Formatted Abstract/Summary
Epithermal deposits are important sources of gold and silver that form at <1.5-km depth and <300°C in high-temperature, mainly subaerial hydrothermal systems. Such hydrothermal systems commonly develop in association with calc-alkaline to alkaline magmatism, in volcanic arcs at convergent plate margins, as well as in intra-arc, back-arc, and postcollisional rift settings. Many important deposits are Tertiary and younger in age and are concentrated around the Pacific Rim and in the Mediterranean and Carpathian regions of Europe. Older deposits occur in the Tethyan arc from Europe to Asia and others are scattered in volcanic arcs of all ages with rare examples as old as Archean. Precious metal mineralization develops in zones of high paleopermeability, hosted within sequences of coeval volcanic and underlying basement rocks. Veins with steep dips are common and these tend to host highest grade ores. Precious metal mineralization also occurs in breccias, coarse clastic rocks, and intensely leached rocks; such disseminated ore is much lower in grade but greater in total tonnage and may be amenable to bulk mining methods. Deposits and districts, comprising one or more orebodies, cover areas from <10 to ~200 km2. Epithermal deposits have been classified on the basis of alteration and gangue mineral assemblages, metal contents, sulfide contents, and sulfide mineral assemblages, and each classification scheme has its merits. Because ores are oxidized by weathering, we prefer a classification that utilizes gangue mineral assemblages. We describe two types of mineralization associated with quartz ± calcite ± adularia ± illite and quartz + alunite ± pyrophyllite ± dickite ± kaolinite assemblages, which reflect the pH of hydrothermal solutions.
Q-Index Code BX
Q-Index Status Provisional Code
Institutional Status Unknown
Additional Notes This book is the "100th Anniversary Volume" of "Economic Geology and the Bulletin of the Society of Economic Geologists", (ISSN: 0361-0128; 1554-0774), but is not included in the Journal numeration. Published under "Ore Deposit Types" as Paper 100 ODT100.

 
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Created: Fri, 13 Feb 2009, 09:05:50 EST by Maryanne Watson on behalf of School of Earth Sciences