Description: Objective: This project seeks to improve the application of noble gas isotope studies to multiphase fluid processes in the Earth's crust by (1) identifying the important noble gas carrier phases in sediments to address the processes that have led to the observed enrichment and depletion patterns in sedimentary rocks and fluids, (2) examine the mechanisms by which such noble gas patterns are acquired, trapped and subsequently released to mobile crustal fluids, and (3) evaluate the time and length scales for the transport of noble gas components, such as radiogenic 4He, through the continental crust.. Project Description: Sedimentary rocks and oil field gases typically are enriched in heavy noble gases: Xe/Ar ratios of ~10-10,000 times the ratio in air have been observed that cannot be explained by adsorption hypotheses. Laboratory experiments designed to isolate sedimentary phases for noble gas analysis are conducted to identify the carrier phase(s). It has been observed that radiogenic 4He accumulates in confined aquifer waters at rates that exceed the rate of local production and approaching the whole crustal production rate. A literature evaluation of 4He, 3He crustal fluxes is being conducted to evaluate crustal scale mass transport in terms of the rate, mechanisms, temporal and spatial variability and the role played by tectonic processes. Results: The laboratory study has concentrated on noble gas abundances in a variety of sedimentary silica samples. We have found that, in general, samples of inorganic silica have noble gas abundances that are consistent with occlusion of air-saturated water in fluid inclusions and lack requisite enrichment/depletion factors needed to explain the noble gas inventory in oil field fluids. However, numerous replicate analyses of noble gases extracted from silica spicules from live sponges (Calyxnicaeensis) show significantly enriched Ar, Kr, and Xe concentrations ([iNg]sample/[iNg]asw > 1), but with very little if any mass dependence ...
Date: March 25, 2011
Creator: Torgerson, Thomas & Kennedy, B. M.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department