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Highest temperatures recorded by the Oklo mineral phase assemblages and rock textures

Description: Biotite-bearing pelitic phase assemblages are observed in reactor zones 2 and 5 and up to at least 4 m outside of zone 2, indicating a minimum temperature in these regions of about 400/sup 0/C. Rock textures suggest that still higher temperatures may have been reached within the reactors.
Date: January 1, 1977
Creator: Vidale, R.
Partner: UNT Libraries Government Documents Department

Two dynamic hydrothermal systems and fluid samplers for studying rock-fluid interactions

Description: Two circulation systems have been designed, built, and tested over the last three years. These systems greatly aid in the study of rock-fluid interactions under flow conditions. A solution sampler has also been developed for fluid extraction under the pressure and temperature conditions of the experiment, eliminating fractionation on sampling.
Date: April 1, 1979
Creator: Charles, R.W.; Bayhurst, G.K. & Vidale, R.J.
Partner: UNT Libraries Government Documents Department

Water geochemistry of the Lucero Uplift, New Mexico: geothermal investigation of low-temperature mineralized fluids

Description: A detailed geochemical investigation of 27 waters of the Lucero uplift, central New Mexico, was performed to determine if the fluids originate from a high-temperature geothermal system along the Rio Grande rift. Two types of mineralized water issue from the Lucero region: a relatively saline (high-Cl, high-SO/sub 4/) type and a relatively dilute (low-Cl, high-SO/sub 4/) type. Emergence temperatures of both types range from 12 to 26/sup 0/C. Chemical data and thermodynamic and geothermometer calculations all indicate that both water types are in equilibrium with carbonate and evaporite minerals found in local Colorado Plateau rocks at surface temperatures or slightly higher. Stable isotope data do not indicate high-temperature rock-water interaction. Although evidence is seen for mixing between mineralized waters and dilute surface waters, no evidence for mixing of a deep hot fluid and surface waters is seen. Dilute mineral waters, which issue from a large area of Chinle Formation on the west side of the Lucero uplift, may be useful for low-temperature geothermal applications with appropriate design of equipment. Saline mineral waters, which leak from a zone of faulted and folded rocks along the Comanche fault zone, do not appear to have much, if any, geothermal potential due to their low-temperature, restricted distribution, and high concentration of dissolved solids. No evidence that saline mineral waters are associated with Quaternary faults of the Rio Grande rift or Quaternary basaltic volcanism within the immediate area is seen.
Date: April 1, 1983
Creator: Goff, F.; McCormick, T.; Gardner, J.N.; Trujillo, P.E.; Counce, D.; Vidale, R. et al.
Partner: UNT Libraries Government Documents Department

Geochemical considerations for Hot, Dry Rock Systems

Description: Circulating systems intended to model the P-T conditions found in the natural HDR (Hot Dry Rock) geothermal system at Los Alamos have been built. Experiments with these systems have determined the following parameters for the ''down hole'' reservoir: sample weight loss, circulating solution composition, textural changes in the rock, mineral loss from the rock and effects of chemical additives on rock erosion. The analyses of solutions generated from rock-water interactions in the experimental systems show the extremely dilute nature of the working fluid. These solutions are not brines. Silica scaling in the surface heat exchanger was found to account for the difference between loss of sample rate and analyzed silica in the solution. The weight loss data indicate that there was continuous transport of silica from the ''down hole'' rock to the heat exchanger. Experiments contrasting felsic and mafic rocks in the HDR concept indicate that a reservoir consisting of glass bearing basaltic rock would tend to produce greater scaling problems than systems emplaced in granite. Experimental results suggest that Na{sub 2}CO{sub 3} solutions may provide a means of increasing permeability and thereby increasing the effective heat transfer area of the reservoir. A brief description is given of a small test loop for simulating the flow of a geothermal solution through a heat exchanger. This loop, which is being built, will be used to study the coagulation and precipitation of silica under conditions similar to those expected in the field.
Date: January 1, 1976
Creator: Balagna, J.; Blatz, L.; Charles, R.; Feber, R.; Herrick, C.; Holley, C. et al.
Partner: UNT Libraries Government Documents Department

Search for other natural fission reactors

Description: Precambrian uranium ores have been surveyed for evidence of other natural fission reactors. The requirements for formation of a natural reactor direct investigations to uranium deposits with large, high-grade ore zones. Massive zones with volumes approximately greater than 1 m/sup 3/ and concentrations approximately greater than 20 percent uranium are likely places for a fossil reactor if they are approximately greater than 0.6 b.a. old and if they contained sufficient water but lacked neutron-absorbing impurities. While uranium deposits of northern Canada and northern Australia have received most attention, ore samples have been obtained from the following worldwide locations: the Shinkolobwe and Katanga regions of Zaire; Southwest Africa; Rio Grande do Norte, Brazil; the Jabiluka, Nabarlek, Koongarra, Ranger, and El Sharana ore bodies of the Northern Territory, Australia; the Beaverlodge, Maurice Bay, Key Lake, Cluff Lake, and Rabbit Lake ore bodies and the Great Bear Lake region, Canada. The ore samples were tested for isotopic variations in uranium, neodymium, samarium, and ruthenium which would indicate natural fission. Isotopic anomalies were not detected. Criticality was not achieved in these deposits because they did not have sufficient /sup 235/U content (a function of age and total uranium content) and/or because they had significant impurities and insufficient moderation. A uranium mill monitoring technique has been considered where the ''yellowcake'' output from appropriate mills would be monitored for isotopic alterations indicative of the exhumation and processing of a natural reactor.
Date: January 1, 1977
Creator: Apt, K.E.; Balagna, J.P.; Bryant, E.A.; Cowan, G.A.; Daniels, W.R. & Vidale, R.J.
Partner: UNT Libraries Government Documents Department