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dc.contributor.authorRunyon, Simone E.
dc.contributor.authorNickerson, Phillip A.
dc.contributor.authorSeedorff, Eric
dc.contributor.authorBarton, Mark D.
dc.contributor.authorMazdab, Frank K.
dc.contributor.authorLecumberri-Sánchez, Pilar
dc.contributor.authorSteele-MacInnis, Matthew
dc.date.accessioned2019-07-16T18:16:53Z
dc.date.available2019-07-16T18:16:53Z
dc.date.issued2019-06-01
dc.identifier.citationRunyon, S. E., Nickerson, P. A., Seedorff, E., Barton, M. D., Mazdab, F. K., Lecumberri-Sánchez, P., & Steele-MacInnis, M. (2019). Sodic-Calcic Family of Alteration in Porphyry Systems of Arizona and Adjacent New Mexico. Economic Geology, 114(4), 745-770.en_US
dc.identifier.issn0361-0128
dc.identifier.doi10.5382/econgeo.4661
dc.identifier.urihttp://hdl.handle.net/10150/633367
dc.description.abstractSodic-calcic alteration has affected numerous districts with Laramide porphyry systems across Arizona and New Mexico. Previously undocumented Na-Ca alteration has been identified at Charleston, Sycamore Canyon, Silver Bell, and the Ninetysix Hills in Arizona and the Central mining district in New Mexico. These new occurrences are compared to sodic-calcic alteration at the Sierrita-Esperanza deposit (Pima district), the Ajo mining district, the Tea Cup pluton (Kelvin-Riverside district), and the Eagle Pass dike swarm in Arizona. Spatial positions, crosscutting relationships, and mineral assemblages and compositions allow for interpretation of the geochemical conditions of formation and implications for associated hydrothermal processes. Diopside- or andradite-grossular solid solution (Ad(68)-Ad(72))-stable assemblages representative of calcic alteration typically occur in deep and/or distal positions but are less commonly exposed. The sodic-calcic and sodic alteration types, however, occur more proximally to the porphyry orebody. Sodic-calcic assemblages containing Na plagioclase (An(10)-An(33))-Ca amphibole +/- epidote are focused along granite cupolas near the base of orebodies, and these grade into shallower sodic assemblages containing albite (An(00)-An(09))-epidote-chlorite. Mineral composition and fluid inclusion data suggest that Na-Ca plagioclase-bearing assemblages form at higher temperatures (360 degrees-470 degrees C+) than later, lower-temperature albite-epidote assemblages (>250 degrees C). Calculated delta D isotope compositions of fluids in equilibrium with Na-Ca alteration minerals span a broad range (-46 to -1%) and are consistently less negative than magmatic fluids. Where members of the Na-Ca family of alteration assemblages are present in porphyry systems, many lines of evidence-including isotopic compositions of minerals and the geologic alteration zoning patterns-are consistent with an origin by incursion of saline external fluids. Where Na-Ca alteration is present, it is best developed at relatively deep levels of porphyry systems. Several Laramide systems that are well exposed at comparably deep levels lack Na-Ca alteration, probably because sources of saline fluid were absent or hydrologic conditions were unfavorable for the incursion of saline external fluids. Though similar in temperatures, isotopic compositions, mineral assemblages, and zoning patterns, Na-Ca alteration in Laramide systems is volumetrically smaller than in Jurassic systems documented in the western United States, probably because saline external fluids were much less abundant during the Laramide after a tectonically driven excursion in paleoclimate from arid to humid conditions.en_US
dc.description.sponsorshipGeological Society of America; Society of Economic Geologistsen_US
dc.language.isoenen_US
dc.publisherSociety of Economic Geologistsen_US
dc.rights© 2019 Society of Economic Geologists, Inc.en_US
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/
dc.titleSodic-Calcic Family of Alteration in Porphyry Systems of Arizona and Adjacent New Mexicoen_US
dc.typeArticleen_US
dc.identifier.eissn1554-0774
dc.contributor.departmentUniv Arizona, Dept Geoscien_US
dc.identifier.journalECONOMIC GEOLOGYen_US
dc.description.note12 month embargo; published 01 June 2019en_US
dc.description.collectioninformationThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.en_US
dc.eprint.versionFinal accepted manuscripten_US
dc.source.volume114
dc.source.issue4
dc.source.beginpage745-770


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