HR: 0800h
AN: V51A-0514    [Abstracts]
TI: LA-MC-ICPMS Determination of Copper Isotope Ratios in Turquoise from the Southwestern United States.
AU: * Evans, M J
EM: evansmj@ornl.gov
AF: Oak Ridge National Lab, P.O. Box 2008, Oak Ridge, TN 37831-6375 United States
AU: Fayek, M
AF: Earth and Planetary Sciences, University of Tennessee, 306 Geology Building, Knoxville, TN 37996 United States
AU: Riciputi, L
AF: Oak Ridge National Lab, P.O. Box 2008, Oak Ridge, TN 37831-6375 United States
AU: Anovitz, L
AF: Earth and Planetary Sciences, University of Tennessee, 306 Geology Building, Knoxville, TN 37996 United States
AU: Hull, S
AF: Earth and Planetary Sciences, University of Tennessee, 306 Geology Building, Knoxville, TN 37996 United States
AU: Mathien, F J
AF: Anthropology Program National Park Service, P.O. Box 728, Santa Fe, NM 87504-0728 United States
AU: Milford, H
AF: Anthropology Program National Park Service, P.O. Box 728, Santa Fe, NM 87504-0728 United States
AB: Hydrothermal circulation driven by igneous intrusion led to the deposition of turquoise throughout the southwestern United States and Mesoamerica. The genesis of these copper-ore deposits is unclear; conflicting hypotheses call on ascent of magmatic waters (hypogene) or descent and recirculation of meteroric waters (supergene). Copper isotope analyses were performed by laser-ablation multi-collector ICPMS to survey turquoise deposits from AZ, NV, CA, NM, and CO. The turquoise have [Cu] from 0.1 to 10 wt% and are all found in near-surface alteration zones. Analyses of individual turquoise grains are reproducible to better than 0.4\permil \delta$^{65}$Cu (1\sigma) (relative to NBS-976). \delta$^{65}$Cu values show significant variation (ca. 10\permil) between the deposits, equal to the total range reported for continental ores and both hypogene and supergene deposits. The variability between deposits may reflect differences in source Cu isotopic composition or more likely, hydrothermal processes during leaching and deposition. The mining and trade of turquoise played an important role in early social and economic development between Mesoamerica and N. America. Copper isotopes will improve differentiation between turquoise source areas, aiding archaeological and cultural studies of trade between and within Mesoamerica and the SW USA. Research sponsored by NSF-BCS (Archaeology) grant #0312088 to Fayek and the Office of Basic Energy Sciences, U.S. Department of Energy, under contract with Oak Ridge National Laboratory, managed by UT-Battelle, LLC. The submitted manuscript has been authored by a contractor of the U.S. Government under contract No. DE-AC05-00OR22725. Accordingly, the U.S. Government retains a nonexclusive, royalty-free license to publish or reproduce the published form of this contribution, or allow others to do so, for U.S. Government purposes.
DE: 8424 Hydrothermal systems (8135)
DE: 3665 Mineral occurrences and deposits
DE: 1040 Isotopic composition/chemistry
DE: 1094 Instruments and techniques
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting