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At least 1,117 records · Page 62
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

A brief description of geological and geophysical exploration of the Marysville geothermal area

Extensive geological and geophysical surveys were carried out at the Marysville geothermal area during 1973 and 1974. The area has high heat flow (up to microcalories per square centimeter-second, a negative gravity anomaly, high electrical resistivity, low seismic ground noise, and nearby microseismic activity. Significant magnetic and infrared anomalies are not associated with the geothermal area. The geothermal anomaly occupies the axial portion of a dome in Precambrian sedimentary rocks intruded by Cretaceous and Cenozoic granitic rocks. The results from a 2.4-km-deep test well indicate that the cause of the geothermal anomaly is hydrothermal convection in a Cenozoic intrusive. A maximum temperature of 95 C was measured at a depth of 500 m in the test well.

Blackwell, D. D.↗
NASA NTRS1974

Geothermal reservoir engineering research

The Stanford University research program on the study of stimulation and reservoir engineering of geothermal resources commenced as an interdisciplinary program in September, 1972. The broad objectives of this program have been: (1) the development of experimental and computational data to evaluate the optimum performance of fracture-stimulated geothermal reservoirs; (2) the development of a geothermal reservoir model to evaluate important thermophysical, hydrodynamic, and chemical parameters based on fluid-energy-volume balances as part of standard reservoir engineering practice; and (3) the construction of a laboratory model of an explosion-produced chimney to obtain experimental data on the processes of in-place boiling, moving flash fronts, and two-phase flow in porous and fractured hydrothermal reservoirs.

Ramey, H. J., Jr.↗
NASA NTRS1974

Ion-absorption band analysis for the discrimination of iron-rich zones

The author has identified the following significant results. A technique which combines digital computer processing and color composition was devised for detecting hydrothermally altered areas and for discriminating among many rock types in an area in south-central Nevada. Subtle spectral reflectance differences among the rock types are enhanced by ratioing and contrast-stretching MSS radiance values for form ratio images which subsequently are displayed in color-ratio composites. Landform analysis of Nevada shows that linear features compiled without respect to length results in approximately 25 percent coincidence with mapped faults. About 80 percent of the major lineaments coincides with mapped faults, and substantial extension of locally mapped faults is commonly indicated. Seven major lineament systems appear to be old zones of crustal weakness which have provided preferred conduits for rising magma through periodic reactivation.

Rowan, L. C.↗
NASA NTRS1974

Geochemical affinities of cobalt and germanium toward metal, silicate, and sulfide phases at high temperature

Hydrothermal studies indicate that Co and Ge are strongly siderophile when metallic iron is in equilibrium with olivine at 900 C and 500 bars. If the metal is replaced by troilite (FeS), Ge is strongly lithophile whereas Co tends to concentrate in the sulfide phase. If iron meteorites were formed in a core derived from the sulfide phase, they would be depleted in Ge but retain Co.

Wai, C. M.↗
NASA NTRS1974

Skylab S-192 ratio codes of soil, mineral, and rock spectra for ratio image selection and interpretation

A limited theoretical systems study is made of the Skylab S-192 12-channel multispectral scanner's capabilities for geological remote sensing. Laboratory spectra of rocks, minerals, soils, and some vegetation were used to rank the twelve channels and the best twelve of the 66 possible nonreciprocal spectral ratios according to their ability to discriminate among 17 classes of geological targets. Environmental and instrumental noise sources were ignored. The S-192 should be most useful for discriminating minerals deposited by hydrothermal alteration, weathering, and evaporation. Discrimination of igneous rocks will be difficult. Ratio images are recommended over automatic discrimination methods for those geological targets that can be enhanced by ratio imaging. Ratio codes were found for the twelve highest ranked ratios, for use in selecting the ratio images which will best enhance a target of interest. They can also be searched for false alarm candidates for a given target.

Vincent, R. K.↗
NASA NTRS1976

Detection and mapping of mineralized areas in the Cortez-Uinta Belt, Utah-Nevada, using computer-enhanced ERTS imagery

The author has identified the following significant results. Preliminary analysis indicates that mineralogical differences between altered rocks and most unaltered rocks in south-central Nevada cause visible and near infrared spectral reflectance differences, which can be used to discriminate these broad categories of rocks in multispectral images. The most important mineralogical differences are the increased abundance of goethite, hematite, and jarosite, and the presence of alunite, montmorillonite, and kaolinite in the altered rock. The technique to enhance subtle spectral differences combines ratioing of the MSS bands and contrast stretching. The stretched ratio values are used to produce black and white images that depict materials according to spectral reflectance; rationing minimizes the influence of topography and overall albedo on the grouping of spectrally similar materials. Field evaluation of color-ratio composite shows that, excluding alluvial areas, approximately 80 percent of the green and brown color patterns are related to hydrothermal alternation. The remaining 20 percent consists mainly of pink hematitic crystallized tuff, a result of vapor phase crystallization, and of tan and red ferruginous shale and siltstone.

Rowan, L. C.↗
NASA NTRS1975

A search for sulfide-bearing areas using LANDSAT-1 data and digital image-processing techniques

Two experiments were conducted using LANDSAT-1 multispectral scanner data to identify ground features that are indicators of sulfide-bearing rock. A nearby known sulfide deposit was used as a control. In the first experiment, false-color composites were examined visually to locate possible favorable areas; in the second, favorable areas were classified by digital-computer processing. The results of the experiment show that outcrops of hydrothermally altered and mineralized rock can be identified from LANDSAT-1 data under favorable conditions. The empirical method of digital-computer classification of the multispectral scanner data was relatively unrefined and rapid. The five mineralized prospecting sites identified are in locations that the geologist would not have selected as favorable on the basis of geologic knowledge or photogeologic interpretation at the time of the investigation.

Schmidt, R. G.↗
NASA NTRS1976

Detection and mapping of mineralized areas in the Cortez-Uinta Belt, Utah-Nevada using computer-enhanced ERTS imagery

The author has identified the following significant results. The reflectance spectra of most hydrothermally altered rocks were characterized by broad ferric iron absorption bands short of 1.1 microns and a sharper hydroxyl band near 2.2 microns; maximum reflectance occurred near 1.6 microns. Their features became more prominent as albedo increased. The MSS color ratio composite images were the most effective and practical means for detecting and mapping limonitic rocks in areas having less than about 50 percent desert brush cover and less than 25-35 percent coniferous tree cover. Limonitic altered and unaltered rocks could not be distinguished in MSS color ratio composite images.

Rowan, L. C.↗
NASA NTRS1976

Geothermal flux through palagonitized tephra, Surtsey, Iceland - The Surtsey temperature-data-relay experiment via Landsat-1

The net geothermal flux through palagonitized basaltic tephra rims of the Surtur I and Surtur II craters at Surtsey, Iceland, in 1972, is estimated at 780 plus or minus 325 microcal/sq cm/s, indicating a decline since 1969 when a flux of 1500 microcal/sq cm/s was estimated. Heat flux in this range characterizes the postvolcanic environment on Surtsey in which the subaerial polagonitization of basaltic tephra is associated with mass transfer of hydrothermal vapor, either of meteoric or sea-water origin, only a few years after cessation of eruptive activity. The flux estimation is the result of the Surtsey data-relay experiment via Landsat-1 which was carried out in several phases. Temperature data were transmitted for a 38-day period in November and December 1972. A near-surface vertical gradient of 69.4 C/m was obtained, suggesting a mixed mechanism of heat transfer, partitioned between conduction and convection.

Friedman, J. D.↗
NASA NTRS1979

Solar-powered hot-water system

Hot-water system requires no external power except solar energy. System is completely self-controlling. It includes solar-powered pump, solar-thermally and hydrothermally operated valves, and storage tank filled with open-celled foam, to maintain thermal stratification in stored water.

Collins, E. R.↗
NASA NTRS1977

An Integrated Theory for Predicting the Hydrothermomechanical Response of Advanced Composite Structural Components

An integrated theory is developed for predicting the hydrothermomechanical (HDTM) response of fiber composite components. The integrated theory is based on a combined theoretical and experimental investigation. In addition to predicting the HDTM response of components, the theory is structured to assess the combined hydrothermal effects on the mechanical properties of unidirectional composites loaded along the material axis and off-axis, and those of angleplied laminates. The theory developed predicts values which are in good agreement with measured data at the micromechanics, macromechanics, laminate analysis and structural analysis levels.

Chamis, C. C.↗
NASA NTRS1977

Digital color analysis of color-ratio composite LANDSAT scenes

A method is presented that can be used to calculate approximate Munsell coordinates of the colors produced by making a color composite from three registered images. Applied to the LANDSAT MSS data of the Goldfield, Nevada, area, this method permits precise and quantitative definition of the limonitic areas originally observed in a LANDSAT color ratio composite. In addition, areas of transported limonite can be discriminated from the limonite in the hydrothermally altered areas of the Goldfield mining district. From the analysis, the numerical distinction between limonitic and nonlimonitic ground is generally less than 3% using the LANDSAT bands and as much as 8% in ratios of LANDSAT MSS bands.

Raines, G. L.↗
NASA NTRS1978

Selection of a seventh spectral band for the LANDSAT-D thematic mapper

The author has identified the following significant results. Each of the candidate bands were examined in terms of the feasibility of gathering high quality imagery from space while taking into account solar illumination, atmospheric attenuation, and the signal/noise ratio achievable within the TM sensor constraints. For the 2.2 micron region and the thermal IR region, inband signal values were calculated from representative spectral reflectance/emittance curves and a linear discriminant analysis was employed to predict classification accuracies. Based upon the substantial improvement (from 78 t0 92%) in discriminating zones of hydrothermally altered rocks from unaltered zones, over a broad range of observation conditions, a 2.08-2.35 micron spectral band having a ground resolution of 30 meters was recommended.

Holmes, Q. A.↗
NASA NTRS1977

An integrated theory for predicting the hydrothermomechanical response of advanced composite structural components

A theory is developed for predicting the hydrothermomechanical response of advanced composite structural components. The combined hydrothermal effects on the mechanical properties of unidirectional composites loaded along the material axis and off-axis, and of angleplied laminates are also evaluated. The materials investigated consist of neat PR-288 epoxy matrix resin and an AS-type graphite fiber/PR-288 resin unidirectional composite.

Chamis, C. C.↗
NASA NTRS1978

Martian intrusions - Possible sites and implications

Both the Moon and Mars exhibit volcanic modification of impact craters characterized by subfloor intrusions that either lift the old crater floor or result in extrusions of lava. Endogenic modification of martian craters, however, probably has involved interactions between such intrusive bodies and permafrost, as suggested by differences between lunar and martian floor-fractured craters. Such interactions raise the interesting possibility for hydrothermally concentrating ores in a manner analogous to the Sudbury structure on the Earth that may be consistent with interpretations of Viking lander results.

Schultz, P. H.↗
NASA NTRS1979

Altered rock spectra in the visible and near infrared

The author has identified the following significant results. Visible and near-infrared (0.35 to 2.5 micron m) bidirectional reflection spectra recorded for a suite of well-characterized hydrothermally altered rock samples typically display well defined bands caused by both electronic and vibrational processes in the individual mineral constituents. Electronic transitions in the iron-bearing constituent minerals produce diagnostic minima near 0.43, 0.65, 0.85, and 0.93 micron m. Vibrational transitions in clay and water-bearing mineral constituents produce characteristic single or multiple features over limited spectral ranges near 1.4, 1.75, 1.9, 2.2, and 2.35 micron m. The most abundant feature-producing minerals present in these rocks are hematite, goethite, and alunite. Others frequently present are jarosite, kaolinite, potassium micas, pyrophyllite, montmorillonite, diaspore, and gypsum. The spectral region near 2.2 micron m is particularly important for detecting altered rocks by remote sensing.

Hunt, G. R.↗
NASA NTRS1978

Application of remote sensing to reconnaissance geologic mapping and mineral exploration

A method of mapping geology at a reconnaissance scale and locating zones of possible hydrothermal alteration has been developed. This method is based on principal component analysis of Landsat digital data and is applied to the desert area of the Chagai Hills, Baluchistan, Pakistan. A method for airborne spectrometric detection of geobotanical anomalies associated with prophyry Cu-Mo mineralization at Heddleston, Montana has also been developed. This method is based on discriminants in the 0.67 micron and 0.79 micron region of the spectrum.

Birnie, R. W.↗
NASA NTRS1980

Equilibrium geochemical modeling of a seasonal thermal energy storage aquifer field test

A geochemical mathematical modeling study designed to investigate the well plugging problems encountered at the Auburn University experimental field tests is summarized. The results, primarily of qualitative interest, include: (1) loss of injectivity was probably due to a combination of native particulate plugging and clay swelling and dispersion; (2) fluid-fluid incompatibilities, hydrothermal reactions, and oxidation reactions were of insignificant magnitude or too slow to have contributed markedly to the plugging; and (3) the potential for and contributions from temperature-induced dissolved gas solubility reductions, capillary boundary layer viscosity increases, and microstructural deformation cannot be deconvolved from the available data.

Stottlemyre, J. S.↗