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At least 343 records · Page 19

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NASA NTRS1973

Pb-207/Pb-206 ages of individual mineral phases in Luna 20 material by ion microprobe mass analysis.

Ion microprobe analyses of returned lunar material have helped to demonstrate that U, Th, and radiogenic Pb are concentrated in small accessory mineral phases. It is possible to measure the isotopic composition of this Pb and obtain a radiometric Pb-207/Pb-206 age for the mineral. The ages so derived compare favorably with crystallization ages determined by conventional methods. A grain mount (22003,2/6) of Luna 20 material was searched for such accessory mineral phases, and two were found. One of these phases give an age of 4.12 plus or minus 0.04 b.y. and the other an age of 4.42 plus or minus 0.11 b.y. Ages of minerals dated by the ion probe in Apollo samples 14310 and 15555 are given for comparison. Data on the upper limit for Pb concentration in the outermost surface layers of free lunar soil particles are also given.

Andersen, C. A.↗

NASA NTRS1973

Bone mineral measurement, experiment M078

Measurement tests revealed few deviations from baseline bone mineral measurements after 56 days in a Skylab-type environment. No mineral change was observed in the right radius. One individual, however, showed a possible mineral loss in the left os calcis and another gained mineral in the right ulna. The cause of the gain is unclear but may be attributable to the heavy exercise routines engaged in by the crewmember in question. Equipment problems were identified during the experiment and rectified.

Rambaut, P. C.↗

NASA NTRS1974

Identification of geostructures of continental crust particularly as they relate to mineral resource evaluation

The author has identified the following significant results. New mineral deposits have recently been discovered in eastern Alaska through application of a hypothesis very similar to one developed in interpretation of Nimbus and ERTS-1 imagery in this investigation, that mineral deposits may be spatially related to a set of crustal linears. The discovery affirms the validity of this hypothesis and provides an additional exploration rationale to the mineral industry. A regional lineation in lakes near Umiat in northern Alaska, suspected to reflect structures in basement and suggesting areas of possible potential for new petroleum exploration, is found to cover a much larger area than previously suspected east of the Colville River, increasing the area of interest. Further application of this same imagery exists in that environmental scars to the tundra resulting from previous ground exploration, if of large size, can be recognized and their natural revegetation monitored by use of ERTS imagery. New geologic data obtained from ERTS-1 images of lowland areas of western northern Alaska facilitates assessing the petroleum potential of this area. Use of the images in field mapping permitted extrapolation of field observations. Mosaics of ERTS-1 images have provided additional data on regional linear sets and on other regional fault trends possibly related to mineralized areas.

Gryc, G.↗

NASA NTRS1977

Remote sensing exploration for metallic mineral resources in central Baja California

Remote sensor data (primarily LANDSAT) was analyzed by photogeologic and computer-assisted enhancement techniques to evaluate the metallic mineral potential of Baja California. Overlays were prepared at 1:1,000,000 and 1:500,000 and included known geologic relationships and mineral occurrences, lineament, drainage and structural patterns, tonal anomalies, and enhancement results. Computer-assisted enhancement and classification of the test sites was performed using the IMAGE 100 system to identify subtle tonal anomalies thought related to mineralization using known sites as analysis guides. Mineral potential maps of Baja California were generated from these analyses and the ten highest priority targets visited. Preliminary assay results (atomic absorption analysis) for the samples recovered showed moderate to high geochemical anomalies for Copper (10 of 12 samples), Zinc (3 of 12 samples) and Lead (4 of 12 samples).

Baker, R. N.↗

NASA NTRS1978

Implications of liquid-liquid distribution coefficients to mineral-liquid partitioning

In order to evaluate the influence of a silicate liquid structure on mineral-liquid partitioning, element partitioning data is obtained for coexisting anhydrous immiscible granitic and ferrobasaltic magmas. It is found that: (1) mineral-liquid distribution coefficients indicate the competition of crystal and liquid for cation incorporation, (2) increased polymerization of the residual liquid during crystal-liquid fractionation increases the mineral-liquid distribution coefficients for high-charge-density cations, (3) incompatible element ratios of low- and high-charge-density cations may vary during crystal-liquid fractionation because of changes in the melt composition and structure, (4) relative solubilities of REE's in melts do not vary with melt polymerization, (5) the changes of Sm/Eu ratios during crystal-liquid fractionation depend on the melt composition, and (6) minor components and volatiles can significantly influence the silicate melt structure and the mineral-liquid distribution coefficients.

Ryerson, F. J.↗

NASA NTRS1979

Release adiabat measurements on minerals: The effect of viscosity

The current inversion of pressure-particle velocity data for release from a high pressure shock state to a pressure-density path is analyzed. It is assumed that the release process is isentropic. It was shown that for geological materials below stresses of 150 GPa, the effective viscosity must be 1000 kg/m/s in order that the viscous (irreversible) work carried out on the material in the shock state remains small compared to the mechanical work recovered upon adiabatic rarefaction. The available data pertaining to the offset of the Rayleigh line from the Hugoniot for minerals, the magnitude of the shear stress in the high pressure shock state for minerals, and the direct measurements of the viscosities of several engineering materials shocked to pressures below 150 GPa yield effective viscosities of 1000 kg/m/s or less. An inferance that this indicates that the conditions for isentropic release of minerals from shock states are achieved, and a conclusion that the application of the Riemann integral to obtain pressure-density states along the release adiabats of minerals in shock experiments is valid are made.

Jeanloz, R.↗

NASA NTRS1982

Portable Radiometer Identifies Minerals in the Field

Hand-held optical instrument aids in identifying minerals in field. Can be used in exploration for minerals on foot or by aircraft. The radiometer is especially suitable for identifying clay and carbonate minerals. Radiometer measures reflectances of mineral at two wavelengths, computes ratio of reflectances, and displays ratio to user.

Goetz, A. F. H.↗

NASA NTRS1981

Ion-exchange chromatography separation applied to mineral recycle in closed systems

As part of the controlled ecological life support system (CELSS) program, a study is being made of mineral separation on ion-exchange columns. The purpose of the mineral separation step is to allow minerals to be recycled from the oxidized waste products of plants, man, and animals for hydroponic food production. In the CELSS application, relatively large quantities of minerals in a broad concentration range must be recovered by the desired system, rather than the trace quantities and very low concentrations treated in analytical applications of ion-exchange chromatography. Experiments have been carried out to assess the parameters pertinent to the scale-up of ion-exchange chromatography and to determine feasibility. Preliminary conclusions are that the column scale-up is in a reasonable size range for the CELSS application. The recycling of a suitable eluent, however, remains a major challenge to the suitability of using ion exchange chromatography in closed systems.

Ballou, E.↗

NASA NTRS1980

Predictions of mineral assemblages in planetary interiors

It is shown that mineral compatibilities in the model system CaO-MgO-Al2O3-SiO2 can be applied to deduce the mineral assemblages expected in planetary interiors and their variation with depth. In general, the available estimates of bulk composition of the terrestrial planets suggest that the terrestrial planets can be divided into two groups based on their predicted mineral assemblages. The terrestrial, Venusian, and lunar bulk compositions are expected to display the following sequence of mineral assemblages with increasing pressure: plagioclase lherzolite, spinel lherzolite, and garnet lherzolite. The sequences expected in Martian and Mercurian are different: spinel-plagioclase wehrlite, spinel lherzolite, and spinel-garnet wehrlite. These assemblages have a major influence on the compositions of liquids produced by melting of these planetary interiors, on the solidus temperatures, and thus on the nature of planetary differentiation and the types of magmas extruded at planetary surfaces.

Stolper, E.↗

NASA NTRS1983

Cavitation pitting and erosion of aluminum 6061-T6 in mineral oil water

Cavitation erosion studies of aluminum 6061-T6 in mineral oil and in ordinary tap water are presented. The maximum erosion rate (MDPR, or mean depth of penetration rate) in mineral oil was about four times that in water. The MDPR in mineral oil decreased continuously with time, but the MDPR in water remained approximately constant. The cavitation pits in mineral oil were of smaller diameter and depth than the pits in water. Treating the pits as spherical segments, we computed the radius r of the sphere. The logarithm of h/a, where h is the pit depth and 2a is the top width of the pit, was linear when plotted against the logarithm of 2r/h - 1.

Rao, B. C. S.↗

NASA NTRS1984

A compilation of mineral occurrences and the relationship of occurrences to structural elements of the Kentucky and Tennessee region

A very prominent magnetic anomaly measured by MAGSAT over the eastern mid-continent of the United States was inferred to have a source region beneath Kentucky and Tennessee. Prominent aeromagnetic and gravity anomalies are also associated with the inferred source region. A crustal model constructed to fit these anomalies interpreted the complex as a large mafic plutonic intrusion of Precambrian age. The complex was named the Kentucky body. It was noticed that the Jessamine Dome, which is a locus of intense faulting and mineralization, occurs near the northern end of the Kentucky body, and that more generally there seemed to be a spatial relationship between mineral occurrence and the body. The relationship between mineral deposits in Kentucky and Tennessee and the Kentucky body was investigated. A compilation of mineral occurrences in the region, classified according to type and age, is presented.

Mayhew, M. A.↗

NASA NTRS1983

Relationships between mineralization and silicic volcanism in the central Andes

Existing models for the genesis of porphyry copper deposits indicate that they formed in granodioritic stocks located in the infrastructure of andesitic stratovolcanoes. It is noted that sites of porphyry-type subvolcanic tin mineralization in the Eastern Cordillera of Bolivia are distinguished by the absence of such andesitic structures. The surface expression of a typical subvolcanic porphyry tin deposit is thought to be an extrusive dome of quartz latite porphyry, sometimes related to a larger caldera structure. Evidence from the El Salvador porphyry copper deposit in the Eocene magmatic belt in Chile indicates that it too may be more closely related to a silicic volcanic structure than to an andesitic stratovolcano. The dome of La Soufriere, Guadeloupe is offered as a modern analog for the surface expression of subvolcanic mineralization processes, with the phreatic eruptions there indicating the formation of hydrothermal breccia bodies in depths. It is pointed out that the occurrence of mineralized porphyries, millions of years after caldera formation, does not necessarily indicate that tin intrusions and mineralization are not genetically related to the subcaldera pluton, but may be a consequence of the long thermal histories (1-10 million years) of the lowermost parts of large plutons.

Francis, P. W.↗

NASA NTRS1984

Spectral reflectance of carbonate minerals and rocks in the visible and near infrared (0.35 - 2.55 microns) and its applications in carbonate petrology

Reflection spectroscopy in the visible and near infrared (0.35 to 2.55 micron) offers a rapid, inexpensive, nondestructive tool for determining the mineralogy and investigating the minor element chemistry of the hard-to-discriminate carbonate minerals, and can, in one step, provide information previously obtainable only by the combined application of two or more analytical techniques. When light interacts with a mineral certain wavelengths are preferentially absorbed. The number, positions, widths and relative intensities of these absorptions are diagnostic of the mineralogy and chemical composition of the sample. At least seven bands due to vibrations of the carbonate radical occur between 1.60 and 2.55 micron. Positions of these bands vary from one carbonae mineral to another and can be used for mineral identification. Cation mass is the primary factor controlling band position; cation radius plays a secondary role.

Gaffey, S. J.↗

NASA NTRS1985

Erosion of aluminum 6061-T6 under cavitation attack in mineral oil and water

Studies of the erosion of aluminum 6061-T6 under cavitation attack in distilled water, ordinary tap water and a viscous mineral oil are presented. The mean depth of penetration for the mineral oil was about 40 percent of that for water at the end of a 40 min test. The mean depth of penetration and its rate did not differ significantly for distilled and tap water. The mean depth of penetration rate for both distilled and tap water increased to a maximum and then decreased with test duration, while that for mineral oil had a maximum during the initial period. The ratio h/2a of the pit depth h to the pit diameter 2a varied from 0.04 to 0.13 in water and from 0.06 to 0.20 in mineral oil. Scanning electron microscopy indicates that the pits are initially formed over the grain boundaries and precipitates while the surface grains are deformed under cavitation attack.

Rao, B. C. S.↗

NASA NTRS1989

Bone mineral measurement using dual energy x ray densitometry

Bone mineral measurements before and after space missions have shown that weightlessness greatly accelerates bone demineralization. Bone mineral losses as high as 1 to 3 percent per month were reported. Highly precise instrumentation is required to monitor this loss and thereby test the efficacy of treatment. During the last year, a significant improvement was made in Dual-Photon Absorptiometry by replacing the radioactive source with an x ray tube. Advantages of this system include: better precision, lower patient dose, better spacial resolution, and shorter scan times. The high precision and low radiation dose of this technique will allow detection of bone mineral changes of less than 1 percent with measurements conducted directly at the sites of interest. This will allow the required bone mineral studies to be completed in a shorter time with greater confidence.

Smith, Steven W.↗

NASA NTRS1990

Mineral mapping at Cuprite, Nevada with a 63-channel imaging spectrometer

Geophysical and Environmental Research Imaging Spectrometer (GERIS) 63-channel scanner data covering the spectral region 0.4 to 2.5 microns were analyzed for the Cuprite mining district, Esmeralda and Nye Counties, Nevada. Individual and spatially averaged spectra extracted from the GERIS data were used to identify the minerals alunite, kaolinite, buddingtonite, and hematite by their spectral characteristics. The images were classified in the spectral domain to produce color-coded image maps of mineral distribution that clearly show the zoned nature of the hydrothermal system. Comparison of the thematic mineral maps with existing geologic and alteration maps demonstrates the utility of imaging spectrometers for producing detailed maps for mineral exploration.

Kruse, F. A.↗

NASA NTRS1989

Availability of a library of infrared (2.1-25.0 microns) mineral spectra

All previously published libraries of infrared mineral spectra are in the form of transmitance. Reflectance spectra are, however, more useful for remote sensing and some potential laboratory applications, such as the use of an infrared microscope for mineral identification on polished sections. This note points out that construction of a new library of infrared (2.1-25.0 microns) mineral spectra is in progress. Both transmittance and reflectance measurements of a selection of 63 different, well-characterized minerals have been published to date. These data are available in both hard copy and digital form.

Salisbury, John W.↗

NASA NTRS1991

Sources of mineral fragments in impact melts 15445 and 15455 - Toward the origin of low-K Fra Mauro basalt

The compositions of major and minor elements in mineral clasts in low-K Fra Mauro (LKFM) are studied in order to gain a deeper understanding of the genesis of LKFM and its primogenitors. The fragments are picked up as the impact melt moves outward from the center of the target. It is suggested that most of the mineral debris found in the melts is derived from troctolites of the Mg-suite. The chemical end member that dominates the LKFM melt matrics is not present as either mineral or lithic clastic debris in these melt rocks. It is proposed that the missing chemical component of LKFM could have been a magma, existing within the crust 3.9 Ga ago, and was either ejected intact to form LKFM melt rocks or was mixed with other shock-melted crusted and mantle rocks to produce the LKFM compositions. Assimilation of lithic and mineral clasts into the melt after breccian assembly is not a significant process and cannot be adduced to explain the LKFM melt/clast dichotomy.

Spudis, P. D.↗