A structural and geochemical study of the Sierrita porphyry copper system, Pima County, Arizona
AuthorJensen, Paul William, 1967-
AdvisorTitley, Spencer R.
MetadataShow full item record
PublisherThe University of Arizona.
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.
AbstractDetailed mapping of the Sierrita-Esperanza orebody has led to a revised interpretation of the Paleocene intrusive units, and a structural model for the emplacement of those units. A left-lateral wrench fault, expressed through Riedel shears, arranged in a flower structure geometry, is proposed to localize the porphyry intrusions, and control mineralization trends. Miocene extensional deformation has not tilted the orebody more than 10°. The San Xavier Thrust is interpreted to be a low angle detachment, upon which the upper plate has moved to the north-northwest approximately 10 km. When the San Xavier "Thrust" ceased movement, a set of low angle normal faults, striking nearly north-south dissected the Sierrita Range. Molybdenite dating, using the Re-Os system, shows that mineralization of the orebody began at 63.5 Ma (±300 ka, 2σ), and ended sometime after 60.0 Ma (±300 ka, 2σ). An isochron of chalcopyrite and pyrite samples with an age of 59.7 Ma (±17.1 Ma, 2σ), and an initial 187Os/188Os of.152 (±0.33, 2σ) suggests that the lower crust beneath the Sierrita Range has a low 187Os/188Os ratio.
Degree ProgramGraduate College