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Archean gold mineralization and oxidized hydrothermal fluids

Eion M. Cameron and Keiko Hattori
Archean gold mineralization and oxidized hydrothermal fluids
Economic Geology and the Bulletin of the Society of Economic Geologists (August 1987) 82 (5): 1177-1191


Sulfate minerals, hematite, and isotopically fractionated sulfides are relatively rare in rocks of Archean age. Several Archean Au deposits, however, contain one or more of these features indicative of oxidized hydrothermal fluids. They include Hemlo, McIntyre-Hollinger, Macassa, Lake Shore, and Ross which are all in Ontario, Canada, and Kalgoorlie in Australia. Examples of lesser deposits are in Hislop Township and in the Matachewan area, Ontario, Canada. With the exception of Hemlo, these are quartz-carbonate vein deposits spatially and temporally associated with felsic plutonism. Because metamorphic fluids and Archean surface waters were mostly reducing, the most feasible general source for the fluids was felsic magmas.Parent magmas were relatively oxidized, hydrous, and CO (sub 2) rich. The oxidized character may have favored the incorporation of Au into the partial melt and its partitioning into magmatic aqueous fluids. High contents of CO (sub 2) are conducive to the separation of an aqueous fluid from magma at greater depth than otherwise. Fluid inclusion data support the formation of major Archean Au vein deposits at deeper crustal levels than more recent magmatic-hydrothermal mineralization, such as porphyry Cu deposits. CO (sub 2) -rich fluids can unmix into two phases at relatively high temperatures and pressures: a saline aqueous liquid and a low-salinity, H (sub 2) O-CO (sub 2) liquid. This can cause partitioning of Cl-complexed base metals from other metals including Au, Sb, and As. The extensive carbonatization around most deposits has consistent delta (super 13) C values in the range of juvenile-magmatic CO (sub 2) .

ISSN: 0361-0128
EISSN: 1554-0774
Serial Title: Economic Geology and the Bulletin of the Society of Economic Geologists
Serial Volume: 82
Serial Issue: 5
Title: Archean gold mineralization and oxidized hydrothermal fluids
Affiliation: Geol. Surv. Canada, Ottawa, ON, Canada
Pages: 1177-1191
Published: 198708
Text Language: English
Publisher: Economic Geology Publishing Company, Lancaster, PA, United States
References: 120
Accession Number: 1988-004258
Categories: Economic geology, geology of ore depositsIsotope geochemistry
Document Type: Serial
Bibliographic Level: Analytic
Annotation: Geol. Surv. Can.; Contrib. No. 43086
Illustration Description: illus. incl. 2 tables, geol. sketch maps
S29°30'00" - S29°30'00", E122°00'00" - E122°00'00"
Secondary Affiliation: Univ. Ottawa, CAN, Canada
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Society of Economic Geologists
Update Code: 1988
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