Epithermal mineralization in the Sierra Madre Occidental, and the metallogeny of northwestern Mexico.

Persistent Link:
http://hdl.handle.net/10150/187158
Title:
Epithermal mineralization in the Sierra Madre Occidental, and the metallogeny of northwestern Mexico.
Author:
Staude, John-Mark Gardner.
Issue Date:
1995
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:
Studies of the metallogeny of northwestern Mexico (Baja California to Chihuahua to Durango) at the mining district, geologic province, and regional scale, show that deposit formation and preservation is an intricate interrelationship between magmatism, tectonism, and hydrothermal activity. These are not only complicated by superimposed factors including erosion, enrichment, and cover, but in northern Mexico, tectonic translation as well. Using palinspastic reconstructions the relative positions of geologic units are restored to their pre-extensional configuration. Metallic "belts" are heterogeneous with numerous metal associations and deposit types superimposed in the same area. The reconstructions show that magmatism and mineralization were coeval and coincident. Superimposed environments and processes cover, erode, enrich, and preserve mineralization thus substantially affecting perceived metal distribution. Cover sequences including mid-Tertiary ignimbrites and late Tertiary clastic sediments preserve and commonly conceal mineralization. Mid-Tertiary and older extensional events preserve near surface deposit types (e.g, supergene blankets, Jurassic rift-related deposits). At the Sierra Madre Occidental (SMO) province scale, ore deposit types exhibit enormous variation from adularia sericite-dominated to advanced argillic to closely pluton related. The advanced argillic alteration with gold+/-copper+/-silver deposit types appears related to magmatic centers occurring in both the older (pre-Oligocene) and younger (Oligocene) volcanic sections and is a major focus of this dissertation. Acidic alteration-related deposits make up some of the largest Au occurrences including the Mulatos >2 million ounce gold district. Extensive kaolinitic alteration halos (>8 km²) zoned around a core of vuggy silica and quartz+/-pyrophyllite host enargite-pyrite ores. Sulfide isotopes are near zero δ³⁴S(pyrite) = -5 to -3%; δ³⁴S(enargite) = -6 to -4%) with corresponding barite (δ³⁴S = +18-22%). Phase equilibria and isotopes indicate early pyrophyllite-pyrite ores formed at ∼ 300°C with later barite-pyrite-dickite ores deposited at T = ∼ 260°C. Oxygen and hydrogen isotopes show possible mixing between magmatic and meteoric waters with a late (shallow) meteoric (heavier D, lighter δ¹⁸O) overprint. District tilting (∼ 25°NE) exposes >1.5 km altered section containing two separate centers. Alunite occurs late, rarely and is above pyrophyllite, suggesting a vertical transition in acid sulfate systems.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Minerals -- Sierra Madre Occidental (Mexico); Metallogeny -- Mexico.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Geosciences; Graduate College
Degree Grantor:
University of Arizona
Committee Chair:
Barton, Mark D.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleEpithermal mineralization in the Sierra Madre Occidental, and the metallogeny of northwestern Mexico.en_US
dc.creatorStaude, John-Mark Gardner.en_US
dc.contributor.authorStaude, John-Mark Gardner.en_US
dc.date.issued1995en_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.abstractStudies of the metallogeny of northwestern Mexico (Baja California to Chihuahua to Durango) at the mining district, geologic province, and regional scale, show that deposit formation and preservation is an intricate interrelationship between magmatism, tectonism, and hydrothermal activity. These are not only complicated by superimposed factors including erosion, enrichment, and cover, but in northern Mexico, tectonic translation as well. Using palinspastic reconstructions the relative positions of geologic units are restored to their pre-extensional configuration. Metallic "belts" are heterogeneous with numerous metal associations and deposit types superimposed in the same area. The reconstructions show that magmatism and mineralization were coeval and coincident. Superimposed environments and processes cover, erode, enrich, and preserve mineralization thus substantially affecting perceived metal distribution. Cover sequences including mid-Tertiary ignimbrites and late Tertiary clastic sediments preserve and commonly conceal mineralization. Mid-Tertiary and older extensional events preserve near surface deposit types (e.g, supergene blankets, Jurassic rift-related deposits). At the Sierra Madre Occidental (SMO) province scale, ore deposit types exhibit enormous variation from adularia sericite-dominated to advanced argillic to closely pluton related. The advanced argillic alteration with gold+/-copper+/-silver deposit types appears related to magmatic centers occurring in both the older (pre-Oligocene) and younger (Oligocene) volcanic sections and is a major focus of this dissertation. Acidic alteration-related deposits make up some of the largest Au occurrences including the Mulatos >2 million ounce gold district. Extensive kaolinitic alteration halos (>8 km²) zoned around a core of vuggy silica and quartz+/-pyrophyllite host enargite-pyrite ores. Sulfide isotopes are near zero δ³⁴S(pyrite) = -5 to -3%; δ³⁴S(enargite) = -6 to -4%) with corresponding barite (δ³⁴S = +18-22%). Phase equilibria and isotopes indicate early pyrophyllite-pyrite ores formed at ∼ 300°C with later barite-pyrite-dickite ores deposited at T = ∼ 260°C. Oxygen and hydrogen isotopes show possible mixing between magmatic and meteoric waters with a late (shallow) meteoric (heavier D, lighter δ¹⁸O) overprint. District tilting (∼ 25°NE) exposes >1.5 km altered section containing two separate centers. Alunite occurs late, rarely and is above pyrophyllite, suggesting a vertical transition in acid sulfate systems.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectMinerals -- Sierra Madre Occidental (Mexico)en_US
dc.subjectMetallogeny -- Mexico.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGeosciencesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.chairBarton, Mark D.en_US
dc.contributor.committeememberTitley, Spenceren_US
dc.contributor.committeememberRuiz, Joaquinen_US
dc.contributor.committeememberHarris, DeVerleen_US
dc.contributor.committeememberBaldwin, Suzanneen_US
dc.identifier.proquest9534666en_US
dc.identifier.oclc706131541en_US
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