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Derivation of S and Pb in Phanerozoic intrusion-related metal deposits from Neoproterozoic sedimentary pyrite, Great Basin, United States

Peter G. Vikre, Simon R. Poulson and Alan E. Koenig
Derivation of S and Pb in Phanerozoic intrusion-related metal deposits from Neoproterozoic sedimentary pyrite, Great Basin, United States
Economic Geology and the Bulletin of the Society of Economic Geologists (August 2011) 106 (5): 883-912

Abstract

The thick (< or =8 km), regionally extensive section of Neoproterozoic siliciclastic strata (terrigenous detrital succession, TDS) in the central and eastern Great Basin contains sedimentary pyrite characterized by mostly high delta (super 34) S values (-11.6 to 40.8 per mil, >70% exceed 10 per mil; 51 analyses) derived from reduction of seawater sulfate, and by markedly radiogenic Pb isotopes ( (super 207) Pb/ (super 204) Pb >19.2; 15 analyses) acquired from clastic detritus eroded from Precambrian cratonal rocks to the east-southeast. In the overlying Paleozoic section, Pb-Zn-Cu-Ag-Au deposits associated with Jurassic, Cretaceous, and Tertiary granitic intrusions (intrusion-related metal deposits) contain galena and other sulfide minerals with S and Pb isotope compositions similar to those of TDS sedimentary pyrite, consistent with derivation of deposit S and Pb from TDS pyrite. Minor element abundances in TDS pyrite (e.g., Pb, Zn, Cu, Ag, and Au) compared to sedimentary and hydrothermal pyrite elsewhere are not noticeably elevated, implying that enrichment in source minerals is not a precondition for intrusion-related metal deposits. Three mechanisms for transferring components of TDS sedimentary pyrite to intrusion-related metal deposits are qualitatively evaluated. One mechanism involves (1) decomposition of TDS pyrite in thermal aureoles of intruding magmas, and (2) aqueous transport and precipitation in thermal or fluid mixing gradients of isotopically heavy S, radiogenic Pb, and possibly other sedimentary pyrite and detrital mineral components, as sulfide minerals in intrusion-related metal deposits. A second mechanism invokes mixing and S isotope exchange in thermal aureoles of Pb and S exsolved from magma and derived from decomposition of sedimentary pyrite. A third mechanism entails melting of TDS strata or assimilation of TDS strata by crustal or mantle magmas. TDS-derived or assimilated magmas ascend, decompress, and exsolve a mixture of TDS volatiles, including isotopically heavy S and radiogenic Pb from sedimentary pyrite, and volatiles acquired from deeper crustal or mantle sources. In the central and eastern Great Basin, the wide distribution and high density of small to mid-sized vein, replacement, and skarn intrusion-related metal deposits in lower Paleozoic rocks that contain TDS sedimentary pyrite S and Pb reflect (1) prolific Jurassic, Cretaceous, and Tertiary magmatism, (2) a regional, substrate reservoir of S and Pb in permeable and homogeneous siliciclastic strata, and (3) relatively small scale concentration of substrate and magmatic components. Large intrusion-related metal deposits in the central and eastern Great Basin acquired S and most Pb from thicker lithospheric sections.


ISSN: 0361-0128
EISSN: 1554-0774
Coden: ECGLAL
Serial Title: Economic Geology and the Bulletin of the Society of Economic Geologists
Serial Volume: 106
Serial Issue: 5
Title: Derivation of S and Pb in Phanerozoic intrusion-related metal deposits from Neoproterozoic sedimentary pyrite, Great Basin, United States
Affiliation: U. S. Geological Survey, Reno, NV, United States
Pages: 883-912
Published: 201108
Text Language: English
Publisher: Economic Geology Publishing Company, Lancaster, PA, United States
References: 164
Accession Number: 2011-087805
Categories: Isotope geochemistryEconomic geology, geology of ore deposits
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. sects., 4 tables, sketch maps
N35°00'00" - N43°00'00", W120°00'00" - W111°00'00"
Secondary Affiliation: University of Nevada, Reno, Mackay School of Earth Sciences and Engineering, Department of Geological Sciences and Engineering, USA, United States
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: 201146
Program Name: USGSOPNon-USGS publications with USGS authors
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