HR: 0800h
AN: P21A-0224    [Abstracts]
TI: Mineral Precipitation in Porous Media: Laboratory Diffusion Experiments as Analogues for Concretion Formation in Utah and on Mars
AU: * Barge, L M
EM: barge@usc.edu
AF: University of Southern California, Department of Earth Sciences, 3651 Trousdale Parkway, Los Angeles, CA 90089, United States
AU: Petruska, J
EM: petruska@usc.edu
AF: University of Southern California, Department of Biological Sciences, 1050 Childs Way, Los Angeles, CA 90089, United States
AU: Potter, S
EM: sally.potter@utah.edu
AF: University of Utah, Department of Geology and Geophysics, 135 S. 1460 E, Salt Lake City, UT 84112, United States
AU: Cho, J
EM: jeeuncho@usc.edu
AF: University of Southern California, Department of Electrical Engineering, 3650 McClintock Ave, Los Angeles, CA 90089, United States
AU: Chan, M
EM: marjorie.chan@utah.edu
AF: University of Utah, Department of Geology and Geophysics, 135 S. 1460 E, Salt Lake City, UT 84112, United States
AU: Nealson, K
EM: knealson@usc.edu
AF: University of Southern California, Department of Earth Sciences, 3651 Trousdale Parkway, Los Angeles, CA 90089, United States
AB: We present results of laboratory gel diffusion experiments designed to simulate the precipitation of iron minerals in natural systems. Liesegang bands and crystals of various iron minerals were formed in aqueous gels, "mini- concretions" of mineral precipitate were formed in both sand and a sand/agarose mixture, and the formation of hollow mineral spheres was observed in gel precipitation experiments where organics were introduced. These mineral structures are analogous to concretion forms observed in the Navajo Sandstone region of Utah, which have been suggested as terrestrial analogs for the "blueberry" hematite concretions on Mars. Iron mineral precipitates (perhaps with a gel precursor) occur in many forms in the Navajo Sandstone, including "mini- concretions" (solid concretions 1-2 mm in diameter), "rind-like" concretions (hollow spheres of hematite several cm in diameter, surrounding a region of sandstone), and Liesegang banding (banded patterns that form at reaction fronts through diffusion of ions from one reservoir to another). On Mars only small (4-5mm) and mini-concretions (~ 1mm) have been observed; Liesegang bands or large rind-like concretions have not yet been discovered. The varying conditions that give rise to each of these mineral structures in the laboratory indicate that the small, spheroidal types of iron precipitates found in the Utah and Martian environments may be diagnostic of the diffusion medium, presence of organics, and characteristics of fluid in that region.
DE: 1042 Mineral and crystal chemistry (3620)
DE: 3620 Mineral and crystal chemistry (1042)
DE: 3665 Mineral occurrences and deposits
DE: 5419 Hydrology and fluvial processes
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting