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Oxygen, hydrogen, sulfur, and carbon isotopes in the Pea Ridge magnetite-apatite deposit, southeast Missouri, and sulfur isotope comparisons to other iron deposits in the region

Craig A. Johnson, Warren C. Day and Robert O. Rye
Oxygen, hydrogen, sulfur, and carbon isotopes in the Pea Ridge magnetite-apatite deposit, southeast Missouri, and sulfur isotope comparisons to other iron deposits in the region (in A special issue devoted to Proterozoic iron oxide-apatite (+ or -REE) and iron oxide copper-gold and affiliated deposits of southeast Missouri, USA, and the Great Bear magmatic zone, Northwest Territories, Canada, John F. Slack (prefacer), Louise Corriveau (prefacer) and Murray W. Hitzman (prefacer))
Economic Geology and the Bulletin of the Society of Economic Geologists (December 2016) 111 (8): 2017-2032

Abstract

Oxygen, hydrogen, sulfur, and carbon isotopes have been analyzed in the Pea Ridge magnetite-apatite deposit, the largest historic producer among the known iron deposits in the southeast Missouri portion of the 1.5 to 1.3 Ga eastern granite-rhyolite province. The data were collected to investigate the sources of ore fluids, conditions of ore formation, and provenance of sulfur, and to improve the general understanding of the copper, gold, and rare earth element potential of iron deposits regionally. The delta (super 18) O values of Pea Ridge magnetite are 1.9 to 4.0 ppm, consistent with a model in which some magnetite crystallized from a melt and other magnetite-perhaps the majority-precipitated from an aqueous fluid of magmatic origin. The delta (super 18) O values of quartz, apatite, actinolite, K-feldspar, sulfates, and calcite are significantly higher, enough so as to indicate growth or equilibration under cooler conditions than magnetite and/or in the presence of a fluid that was not entirely magmatic. A variety of observations, including stable isotope observations, implicate a second fluid that may ultimately have been meteoric in origin and may have been modified by isotopic exchange with rocks or by evaporation during storage in lakes.Sulfur isotope analyses of sulfides from Pea Ridge and seven other mineral deposits in the region reveal two distinct populations that average 3 and 13 ppm. Two sulfur sources are implied. One was probably igneous melts or rocks belonging to the mafic- to intermediate-composition volcanic suite that is present at or near most of the iron deposits; the other was either melts or volcanic rocks that had degassed very extensively, or else volcanic lakes that had trapped rising magmatic gases. The higher delta (super 34) S values correspond to deposits or prospects where copper is noteworthy-the Central Dome portion of the Boss deposit, the Bourbon deposit, and the Vilander prospective area. The correspondence suggests that (1) sulfur either limited the deposition of copper or was cotransported with copper, and (2) sulfur isotope analysis may be useful in evaluating southeast Missouri iron deposits for copper and possibly for gold.


ISSN: 0361-0128
EISSN: 1554-0774
Coden: ECGLAL
Serial Title: Economic Geology and the Bulletin of the Society of Economic Geologists
Serial Volume: 111
Serial Issue: 8
Title: Oxygen, hydrogen, sulfur, and carbon isotopes in the Pea Ridge magnetite-apatite deposit, southeast Missouri, and sulfur isotope comparisons to other iron deposits in the region
Title: A special issue devoted to Proterozoic iron oxide-apatite (+ or -REE) and iron oxide copper-gold and affiliated deposits of southeast Missouri, USA, and the Great Bear magmatic zone, Northwest Territories, Canada
Author(s): Johnson, Craig A.Day, Warren C.Rye, Robert O.
Author(s): Slack, John F.prefacer
Author(s): Corriveau, Louiseprefacer
Author(s): Hitzman, Murray W.prefacer
Affiliation: U. S. Geological Survey, Denver, CO, United States
Affiliation: U. S. Geological Survey, Reston, VA, United States
Pages: 2017-2032
Published: 201612
Text Language: English
Publisher: Economic Geology Publishing Company, Lancaster, PA, United States
References: 109
Accession Number: 2017-004915
Categories: Economic geology, geology of ore depositsIsotope geochemistry
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables, sketch maps
N37°00'00" - N38°15'00", W92°00'00" - W89°00'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Abstract, Copyright, Society of Economic Geologists. Reference includes data from GeoScienceWorld, Alexandria, VA, United States
Update Code: 201704
Program Name: USGSOPNon-USGS publications with USGS authors
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