Three-Dimensional Evolution of Magmatic Hydrothermal Systems, Schultze Granite and Ruby Star Granodiorite, Arizona

Persistent Link:
http://hdl.handle.net/10150/194841
Title:
Three-Dimensional Evolution of Magmatic Hydrothermal Systems, Schultze Granite and Ruby Star Granodiorite, Arizona
Author:
Stavast, William James Andrew
Issue Date:
2006
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:
The biotite bearing Schultze Granite (Globe-Miami district) and the biotite-hornblende bearing Ruby Star Granodiorite (Pima district) compose two intrusive centers that produced multiple porphyry copper deposits during the Laramide orogeny. Both magmatic-hydrothermal systems were dismembered and tilted by Tertiary extension, as indicated by tilted Tertiary sedimentary rocks, paleomagnetic data, and geobarometry, thereby producing extraordinary exposures of these magmatic-hydrothermal systems: ~ 1 to ~10 km (Globe-Miami district) and <1 to>12 km (Pima district). Ages of emplacement range from 68 to 61 Ma for the Schultze Granite and 64 to 58 Ma for the Ruby Star Granodiorite. The plutons were formed by rapid accumulation of magma within short periods of time (~1 m.y.). The Schultze Granite is a high-silica granite and did not evolve chemically with time, except during formation of late porphyry and aplite dikes. Phases of the Ruby Star pluton range from granodiorite to granite, but appear to be distinct intrusive events separated in time by several million years. Each pluton is chemically homogenous with depth, probably due to convection. The low iron contents of biotites suggest that magmas related to porphyry copper deposits have higher oxidation states than typical granitic bodies. Hydrothermal alteration was associated with most phases of each pluton, with multiple alteration types overlapping to create complex centers. Veins persist to >10 km beneath porphyry copper deposits. Deep styles of alteration differ in the two plutons. The Schultze Granite contains biotite veins and greisen veins (coarse-grained muscovite) (~10 km). The Ruby Star Granodiorite contains sodic-calcic alteration (4-8 km) and greisen veins (4-12 km). The sodic-calcic alteration is asymmetrically distributed on the eastern side of the Sierrita deposit and is interpreted to have been created by influx of external sedimentary brines from Paleozoic sedimentary rocks that only are present on the eastern side of the pluton. Greisen alteration occurs late in the hydrothermal history and may be the last fluids that were exsolved from the magma as the magma chamber completely crystallized. These deep alteration styles can be used to predict where porphyry copper deposition may have occurred, which can lead to discoveries in extended terranes.
Type:
text; Electronic Dissertation
Keywords:
porphyry copper; Pima; Globe-Miami; granite
Degree Name:
PhD
Degree Level:
doctoral
Degree Program:
Geosciences; Graduate College
Degree Grantor:
University of Arizona
Advisor:
Seedorff, Eric; Barton, Mark D.
Committee Chair:
Seedorff, Eric

Full metadata record

DC FieldValue Language
dc.language.isoENen_US
dc.titleThree-Dimensional Evolution of Magmatic Hydrothermal Systems, Schultze Granite and Ruby Star Granodiorite, Arizonaen_US
dc.creatorStavast, William James Andrewen_US
dc.contributor.authorStavast, William James Andrewen_US
dc.date.issued2006en_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.abstractThe biotite bearing Schultze Granite (Globe-Miami district) and the biotite-hornblende bearing Ruby Star Granodiorite (Pima district) compose two intrusive centers that produced multiple porphyry copper deposits during the Laramide orogeny. Both magmatic-hydrothermal systems were dismembered and tilted by Tertiary extension, as indicated by tilted Tertiary sedimentary rocks, paleomagnetic data, and geobarometry, thereby producing extraordinary exposures of these magmatic-hydrothermal systems: ~ 1 to ~10 km (Globe-Miami district) and <1 to>12 km (Pima district). Ages of emplacement range from 68 to 61 Ma for the Schultze Granite and 64 to 58 Ma for the Ruby Star Granodiorite. The plutons were formed by rapid accumulation of magma within short periods of time (~1 m.y.). The Schultze Granite is a high-silica granite and did not evolve chemically with time, except during formation of late porphyry and aplite dikes. Phases of the Ruby Star pluton range from granodiorite to granite, but appear to be distinct intrusive events separated in time by several million years. Each pluton is chemically homogenous with depth, probably due to convection. The low iron contents of biotites suggest that magmas related to porphyry copper deposits have higher oxidation states than typical granitic bodies. Hydrothermal alteration was associated with most phases of each pluton, with multiple alteration types overlapping to create complex centers. Veins persist to >10 km beneath porphyry copper deposits. Deep styles of alteration differ in the two plutons. The Schultze Granite contains biotite veins and greisen veins (coarse-grained muscovite) (~10 km). The Ruby Star Granodiorite contains sodic-calcic alteration (4-8 km) and greisen veins (4-12 km). The sodic-calcic alteration is asymmetrically distributed on the eastern side of the Sierrita deposit and is interpreted to have been created by influx of external sedimentary brines from Paleozoic sedimentary rocks that only are present on the eastern side of the pluton. Greisen alteration occurs late in the hydrothermal history and may be the last fluids that were exsolved from the magma as the magma chamber completely crystallized. These deep alteration styles can be used to predict where porphyry copper deposition may have occurred, which can lead to discoveries in extended terranes.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectporphyry copperen_US
dc.subjectPimaen_US
dc.subjectGlobe-Miamien_US
dc.subjectgraniteen_US
thesis.degree.namePhDen_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGeosciencesen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorSeedorff, Ericen_US
dc.contributor.advisorBarton, Mark D.en_US
dc.contributor.chairSeedorff, Ericen_US
dc.contributor.committeememberBarton, Mark D.en_US
dc.contributor.committeememberGehrels, Georgeen_US
dc.contributor.committeememberPatchett, Jonathanen_US
dc.contributor.committeememberDucea, Mihaien_US
dc.identifier.proquest1525en_US
dc.identifier.oclc137356361en_US
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