HR: 0800h
AN: P41A-0918    [Abstracts]
TI: A LASER RIMS Instrument to Date Igneous Rocks using Rb-Sr and Measure Elemental Chemistry
AU: * Osterloo, M M
P41A-0918 AF: University of Hawaii, 2525 Correa Road, Honolulu, HI 96789 United States
AU: Anderson, F S
EM: Anderson@higp.hawaii.edu
AF: University of Hawaii, 2525 Correa Road, Honolulu, HI 96789 United States
AU: Whitaker, T
P41A-0918 AF: Atom Sciences Inc., 114 Ridgeway Center, Oak Ridge, TN 37830 United States
AU: Miller, G
P41A-0918 AF: Southwest Research Institute, 6220 Culebra Rd., San Antonio, TX 78238 United States
AU: Young, D
P41A-0918 AF: Southwest Research Institute, 6220 Culebra Rd., San Antonio, TX 78238 United States
AU: Mahoney, J
P41A-0918 AF: University of Hawaii, 2525 Correa Road, Honolulu, HI 96789 United States
AU: Norman, M
P41A-0918 AF: Australian National University, Research School of Earth Sciences, Canberra, ACT 0200 Australia
AB: Deriving global estimates of planetary geochronology from cratering statistics remains difficult because estimates of the cratering rate for planets other than the Earth and the Moon are poorly constrained. Obtaining an in-situ radiometric date for the surface of a planet provides an important constraint on the rate of crater production. The result of such a measurement is twofold: first an exact date for a local region can be determined, and secondly, global geochronology from cratering statistics becomes significantly more robust. We are building an instrument to obtain a Rubidium-Strontium (Rb-Sr) date using a laser ablation (LA) resonance ionization (RI) technique. The instrument is attractive because it has virtually no moving parts, requires minimal sample preparation, and could work with existing coring and surface grinding technologies. An additional benefit of this technique is that it can obtain elemental abundances with an accuracy of 1% or better, which is sufficient for understanding normative mineralogy, weathering and exposure to water, and sample petrogenesis. Generating a Rb-Sr date using an isochron approach requires measuring 87Sr/86Sr with a precision of better than 0.1% (preferably 0.02%), and measuring 87Rb/86Sr with a precision of better than 1%. We present data that demonstrate that off-the-shelf instruments without any calibration or optimization can measure 87Sr/86Sr using RI to a precision of 0.14%, and 87Rb/86Sr using LA to 0.6%, suggesting that an optimized LA/RI technique could be used to successfully obtain an in-situ radiometric date.
DE: 1040 Radiogenic isotope geochemistry
DE: 5410 Composition (1060, 3672)
DE: 5470 Surface materials and properties
DE: 5480 Volcanism (6063, 8148, 8450)
DE: 5494 Instruments and techniques
SC: Planetary Sciences [P]
MN: Fall Meeting 2005