Geochemistry of Lower Paleozoic host rocks for sediment-hosted gold deposits, western United States

Persistent Link:
http://hdl.handle.net/10150/284127
Title:
Geochemistry of Lower Paleozoic host rocks for sediment-hosted gold deposits, western United States
Author:
Young-Mitchell, Michaela Nicole
Issue Date:
1999
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Lower Paleozoic, passive margin strata host more gold deposits than other Paleozoic strata. Geochemical analysis of unaltered, unmineralized lower Paleozoic sedimentary rocks from Nevada, Arizona, and Australia suggests that the abundance of gold mineralization in lower Paleozoic strata is related to geochemical conditions during sedimentation. Siliciclastic strata show primary gold enrichments of 21 parts per billion (ppb) and 7 ppb (mean values) in Ordovician Valmy and Vinini strata, respectively. Gold contents of lower Paleozoic carbonate platform, shelf, and transitional facies are comparable to the average crustal abundance of ∼2 ppb. Gold concentrations of the siliciclastic rocks correlate stratigraphically with high total organic carbon, total metal contents, vanadium ratio [V/(V+Ni)], and authigenic uranium, and with low δ¹³C(org) and cerium anomaly. These geochemical parameters are indicative of a low-O₂ paleo-environment, interpreted to result from high organic productivity in upwelling zones. The origin of the gold enrichments in lower Paleozoic, siliciclastic strata is related to global conditions in the marine environment during the early Paleozoic. Hydrothermal and detrital inputs of gold to the oceans were higher than at other times. Organic activity in upwelling zones contributed to the accumulation and preservation of gold in marginal marine sediments. Lower Paleozoic strata are favorable hosts for gold mineralization because they are associated with gold-enriched, carbonaceous siliciclastic strata that may act as a source and/or trap for gold-bearing hydrothermal fluids.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Geology.; Geochemistry.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Geosciences
Degree Grantor:
University of Arizona
Advisor:
Titley, Spencer R.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titleGeochemistry of Lower Paleozoic host rocks for sediment-hosted gold deposits, western United Statesen_US
dc.creatorYoung-Mitchell, Michaela Nicoleen_US
dc.contributor.authorYoung-Mitchell, Michaela Nicoleen_US
dc.date.issued1999en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractLower Paleozoic, passive margin strata host more gold deposits than other Paleozoic strata. Geochemical analysis of unaltered, unmineralized lower Paleozoic sedimentary rocks from Nevada, Arizona, and Australia suggests that the abundance of gold mineralization in lower Paleozoic strata is related to geochemical conditions during sedimentation. Siliciclastic strata show primary gold enrichments of 21 parts per billion (ppb) and 7 ppb (mean values) in Ordovician Valmy and Vinini strata, respectively. Gold contents of lower Paleozoic carbonate platform, shelf, and transitional facies are comparable to the average crustal abundance of ∼2 ppb. Gold concentrations of the siliciclastic rocks correlate stratigraphically with high total organic carbon, total metal contents, vanadium ratio [V/(V+Ni)], and authigenic uranium, and with low δ¹³C(org) and cerium anomaly. These geochemical parameters are indicative of a low-O₂ paleo-environment, interpreted to result from high organic productivity in upwelling zones. The origin of the gold enrichments in lower Paleozoic, siliciclastic strata is related to global conditions in the marine environment during the early Paleozoic. Hydrothermal and detrital inputs of gold to the oceans were higher than at other times. Organic activity in upwelling zones contributed to the accumulation and preservation of gold in marginal marine sediments. Lower Paleozoic strata are favorable hosts for gold mineralization because they are associated with gold-enriched, carbonaceous siliciclastic strata that may act as a source and/or trap for gold-bearing hydrothermal fluids.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectGeology.en_US
dc.subjectGeochemistry.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineGeosciencesen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorTitley, Spencer R.en_US
dc.identifier.proquest9927489en_US
dc.identifier.bibrecord.b3956664xen_US
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