Other
Scientific paper
Dec 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007agufm.p31c0544k&link_type=abstract
American Geophysical Union, Fall Meeting 2007, abstract #P31C-0544
Other
1051 Sedimentary Geochemistry, 1830 Groundwater/Surface Water Interaction, 5220 Hydrothermal Systems And Weathering On Other Planets, 5419 Hydrology And Fluvial Processes, 5460 Physical Properties Of Materials
Scientific paper
Thick deposits of evaporitic hydrates can markedly influence heat flow due to the anomalous low thermal conductivity of hydrated salts and the high conductivity of anhydrous salts. The regulation or oscillation of hydration states and generation or freezing of saturated brines can be effected by interactive feedbacks between hydration states, volumes, thermal conductivities, and conductive regimes of hydrated materials. Tens of meters of hydrates can be important on Earth, and hundreds of meters can be crucial on Mars. Brines can exist and saline seeps may occur where none otherwise would. High temperatures beneath hydrate deposits may be attained at comparatively shallow depths even today in cold regions of Mars. Thus, modern and ancient aqueous processes can be linked. On Earth, hydrocarbon maturation and, on Mars and Earth, low-grade metamorphism in the zeolite and prehnite-pumpellyite facies is likely in the upper crust beneath hydrate deposits; zeolites, epidote, chlorite, serpentine, and other minerals are apt to form. Lateral discontinuities or thickenings/thinnings of thick hydrate deposits can cause lateral heat flow and produce surface-propagating zones of increased heat flux, even if the heat flux coming into the base of the deposits is constant. Such "heat leaks" can localize saline springs, gas emissions, and mud volcanism or diapirism, which potentially may be active even today on Mars. Thermal conductivity control of brine migration may transport minor soluble species to specific zones of high near-surface thermal gradient and heat flux. The movement of solutes and water in predictable sites relative to buried evaporitic sequences might result in unique effluorescences and high or low hydration states, depending on circumstances. These may have observable consequences in multispectral and thermal remote sensing and for surface morphologies, such as mud lumps/domes, desiccation cracks, patterns of effluorescence and wetting, and intensities/shapes of near infrared absorption bands due to bound water. Rare evaporite and pegmatite mineralization (e.g., economic borates in the Mojave Desert) that traditionally are attributed to volcanic interactions within evaporitic settings or magmatic/hydrothermal processes (e.g., low-temperature fluorite- bearing veins) might potentially be related to hydrate-associated insulation/heating and zone refining processes in thermally heterogeneous evaporite-hosted groundwater systems. Large bromide fractions in evaporitic halide solid solutions might be generated by fractionations in such systems. With bromine abundances believed to be much higher in the Martian crust than in Earth's, bromides may be an important marker of such fractionations on Mars. The modern viability of Martian habitats may be linked, in places, to this mechanism.
Baldridge Alice
Crowley J.
Furfaro Roberto
Hook S.
Kargel Jeff S.
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