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At least 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

AVIRIS data characteristics and their effects on spectral discrimination of rocks exposed in the Drum Mountains, Utah: Results of a preliminary study

Airborne Visible and Infrared Imaging Spectrometer (AVIRIS) data collected over a geologically diverse field site and over a nearby calibration site were analyzed and interpreted in efforts to document radiometric and geometric characteristics of AVIRIS, quantify and correct for detrimental sensor phenomena, and evaluate the utility of AVIRIS data for discriminating rock types and identifying their constituent mineralogy. AVIRIS data acquired for these studies exhibit a variety of detrimental artifacts and have lower signal-to-noise ratios than expected in the longer wavelength bands. Artifacts are both inherent in the image data and introduced during ground processing, but most may be corrected by appropriate processing techniques. Poor signal-to-noise characteristics of this AVIRIS data set limited the usefulness of the data for lithologic discrimination and mineral identification. Various data calibration techniques, based on field-acquired spectral measurements, were applied to the AVIRIS data. Major absorption features of hydroxyl-bearing minerals were resolved in the spectra of the calibrated AVIRIS data, and the presence of hydroxyl-bearing minerals at the corresponding ground locations was confirmed by field data.

Bailey, G. B.↗
NASA NTRS1988

Post-metamorphic fluid infiltration into granulites from the Adirondack Mountains, USA

Post-metamorphic effects in the anorthosites of the Adirondacks, New York were described. Calcite-chlorite-sericite assemblages occur as veins, in disseminated form and as clots, and document retrograde fluid infiltration. These features are associated with late-state CO2-rich fluid inclusions. Stable isotope analyses of calcites indicates that the retrograde fluids interacted with meta-igneous and supracrustal lithologies, but the precise timing of the retrogression is as yet unknown.

Morrison, J.↗
NASA NTRS1988

Petrology and tectonic development of supracrustal sequence of Kerala Khondalite Belt, Southern India

The granulite terrain of southern India, of which the Kerala Khondalite belt (KKB) is a part, is unique in exposing crustal sections with arrested charnockite growth in different stages of transformation and in varied lithological association. The KKB with rocks of surficial origin and incipient charnockite development, poses several problems relating to the tectonics of burial of vast area and mechanisms involved in expelling initial H2O (causes of dryness) for granulite facies metamorphism. It is possible to infer the following sequence of events based on the field and laboratory studies: (1) derivation of protoliths of KKB from granitic uplands and deposition in fault bounded basin (cratonic rift); (2) subhorizontal deep burial of sediments; (3) intense deformation of infra and supracrustal rocks; (4) early granulite facies metamorphism predating F sub 2 - loss of primary structure in sediments and formation of charnockites from amphibole bearing gneisses and khondalites from pelites; (5) migmatisation and deformation of metasediments and gneisses; (6) second event of charnockite formation probably aided by internal CO2 build-up; and (7) isothermal uplift, entrapment of late CO2 and mixed CO2-H2O fluids, formation of second generation cordierites and cordierite symplectites.

Kumar, G. R. Ravindra↗
NASA NTRS1988

Petrology and geochemistry of the high-pressure Nilgiri Granulite Terrane, Southern India

The Nilgiri granulite terrane in Southern India is predominantly composed of late Archaean medium- to coarse-grained enderbitic to charnockitic rocks. The dominant regional foliation strikes N60 to 70E with generally steep dips. Tight minor isoclinal folds have been observed in places. Granoblastic polygonal micro-structures are common and indicate thorough post-kinematic textural and chemical equilibration at conditions of the granulite facies (2.5 Ga ago). Late compressional deformation in connection with the formation of the Moyar and Bhavani shear zones to the north and south of the Nilgiri block, resulted in wide-spread development of weakly to strongly strained fabrics and was accompanied by minor rehydration. Enderbites and charnockites range from tonalitic to granodioritic in composition. A magmatogenic origin of the protoliths is inferred from their chemical characteristics which resemble those of the andesitic to dacitic members of Cordillera-type calc-alkaline igneous suites. A significant lithological feature of the Nilgiri granulite terrane are numerous extended bodies, lenses and pods of gabbroic and pyroxenitic rocks which are aligned conformable to the foliation of the enderbite-charnockite complex and which have also been deformed and metamorphosed at granulite facies conditions.

Srikantappa, C.↗
NASA NTRS1988

Petrology and provenance of Apollo 15 drive tube 15007/8

The petrology of submillimeter fractions of soils from 13 levels of Apollo 15 drive tube 15007/8 have been studied through grain size analysis, modal analysis of the 90-150 micron sieve fraction, and electron probe microanalysis of monomineralic fragments of olivine, pyroxene, and plagioclase from the soils. It is shown that core 15007/8 does not contain distinct lithologic units and probably contains soils of mixed maturity in which mixing has greatly dominated in situ reworking. No petrologic layering is found in the core. Abundances of KREEP basalts correlate with mare basalts and not with anorthosite, norite, and troctolite components from the Apennine Front. Some olivine and pyroxene fragments with mare basalt affinity are found to be optically and chemically unzoned, suggesting that they may have been derived from unusual source rocks.

Basu, Abhijit↗
NASA NTRS1989

Ferroan anorthosite from lunar breccia 64435 - Implications for the origin and history of lunar ferroan anorthosites

A composite clast of ferroan-anorthosite-suite rocks from lunar breccia 64435 is shown to contain three lithologies. The results suggest that the structures of the 64435 composite clast were produced in an early deformation that consisted of extensive granulation followed by pervasive recrystallization, and that some granulitic breccias are nearly monomict. The REE concentrations in the coarse-grained troctolitic anorthosite are explained in terms of mass balance among the equilibrated phases.

James, O. B.↗
NASA NTRS1989

Spectral characterization of igneous rocks in the 8- to 12-micron region

This paper investigates the crystal-chemistry basis for the variation in spectral behavior of ingneous rocks, with the purpose of developing relationships useful for applications in the lithologic characterization of terrestrial and extraterrestrial surfaces. A new parameter is proposed for characterizing general rock and mineral type. The parameter, SCFM, defined as the ratio SiO2/(SiO2 + CaO + FeO + MgO), reflects the degree of depolymerization of the silica tetrahedra in both fine-grained and coarse-grained igneous rocks, and is a good descriptor of the composition of these rocks. Using spectra obtained in the laboratory on coarse-particulate mineral and solid-rock samples, the SCFM parameter was used to assess the effects of variations in the rock composition on the location, number, and width of spectral bands. A regression analysis of bands varying in width from 0.2 micron to 1.4 microns versus the SCFM value resulted in correlation coefficients ranging from 0.88 to 0.97.

Walter, Louis S.↗
NASA NTRS1989

Evidence for Phanerozoic reactivation of the Najd Fault System in AVHRR, TM, and SPOT images of central Arabia

SPOT stereoscopic and TM multispectral images support evidence in AVHRR thermal-IR images of a major unmapped shear zone in Phanerozoic cover rocks southeast of the ancient Najd Fault System in the Arabian Shield. This shear zone and faults of the Najd share a common alignment, orientation, and sinistral sense of movement. These similarities suggest a 200-km extension of the Najd Fault System and reactivation since it formed in the late Precambrian. Topographic and lithologic features in the TM and SPOT data along one of three faults inferred from the AVHRR data indicate sinistral offsets up to 2.5 km, en echelon folds and secondary faults like those predicted by models of left-lateral strike-slip faulting. The age of the affected outcrops indicates reactivation of Najd faults in the Cretaceous, judging from TM and SPOT data or in the Tertiary, based on AVHRR data. The total length of the system visible at the surface measures 1300 km. If the Najd Fault System is extrapolated beneath sands of the Empty Quarter to faults of a similar trend in South Yemen, the shear zone would span the Arabian Plate. Furthermore, if extensions into the Arabian Sea bed and into Egypt proposed by others are considered, it would exceed 3000 km.

Andre, Constance G.↗
NASA NTRS1990

Use of Landsat Thematic Mapper images in regional correlation of syntectonic strata, Colorado river extensional corridor, California and Arizona

Enhanced Landsat TM images were used in conjunction with field work to investigate the regional correlation of Miocene rocks in the Colorado River extensional corridor of California and Arizona. Based on field investigations, four sequences of sedimentary and volcanic strata could be recognized in the Mohave Mountains (Arizona) and the eastern Whipple Mountains (California), which display significantly different relative volumes and organization of lithologies. The four sequences were also found to have distinctive appearances on the TM image. The recognition criteria derived from field mapping and image interpretation in the Mohave Mountains and Whipple Mountains were applied to an adjacent area in which stratigraphic affinities were less well known. The results of subsequent field work confirmed the stratigraphic and structural relations suggested by the Tm image analysis.

Beratan, K. K.↗
NASA NTRS1990

Faults in the Mojave Desert, California, as revealed on enhanced Landsat images

Landsat TM images, subjected to four-component processing through which lithologies can be discriminated by their contrasting absorption and reflection at IR wavelengths, have revealed previously unsuspected strike-slip and normal faults in the central and eastern Mojave Desert. These discriminations, which extend to ferric and ferrous iron and to hydroxyl content without compromise of landform depiction, represent a novel type of geophysical display for geologic mapping in regions of well-exposed bedrock; the faults thus discovered form part of an extensive regional network of right shear which connects Death Valley region faults with those in the San Andreas system.

Ford, J. P.↗
NASA NTRS1990

Cartographic modeling of snow avalanche path location within Glacier National Park, Montana

Geographic information system (GIS) techniques were applied to the study of snow-avalanche path location within Glacier National Park, Montana. Aerial photointerpretation and field surveys confirmed the location of 121 avalanche paths within the selected study area. Spatial and nonspatial information on each path were integrated using the ARC/INFO GIS. Lithologic, structural, hydrographic, topographic, and land-cover impacts on path location were analyzed. All path frequencies within variable classes were normalized by the area of class occurrence relative to the total area of the study area and were added to the morphometric information contained within INFO tables. The normalized values for each GIS coverage were used to cartographically model, by means of composite factor weightings, avalanche path locations.

Walsh, Stephen J.↗
NASA NTRS1991

Report of the panel on plate motion and deformation, section 2

Given here is a panel report on the goals and objectives, requirements and recommendations for the investigation of plate motion and deformation. The goals are to refine our knowledge of plate motions, study regional and local deformation, and contribute to the solution of important societal problems. The requirements include basic space-positioning measurements, the use of global and regional data sets obtained with space-based techniques, topographic and geoid data to help characterize the internal processes that shape the planet, gravity data to study the density structure at depth and help determine the driving mechanisms for plate tectonics, and satellite images to map lithology, structure and morphology. The most important recommendation of the panel is for the implementation of a world-wide space-geodetic fiducial network to provide a systematic and uniform measure of global strain.

Bock, Yehuda↗
NASA NTRS1990

Chondrule-like objects and brown glasses in howardites

Chondrulelike objects and brown glasses were analyzed in the howardites, Bununu, Malvern, Monticello, Pavlovka, and Yamato 7308. The objects are very similar to chondrules in ordinary and carbonaceous chondrites. Like the brown glasses, the chondrulelike objects could have been produced by impact melting that left some crystalline nuclei, followed by a slower cooling rate than for the glasses. Alternatively, these objects are chondrules implanted from chondrite impactors. They are, however, without rims or any adhering matrix. The brown glasses appear to represent melting of average regolithic surface material, except for Monticello and Y7308, both of which have some siliceous glasses. The siliceous glasses could not have been produced by vapor fractionation but by melting of differentiated lithologies such as fayalitic granites. Impact mechanics indicates that howardites with abundant brown glasses came from an asteroid larger than Vesta (greater than 400 km radius), upon which impacts occurred at relative velocities of up to 5 km/s. Howardites with little or no brown glasses came from a smaller parent body. It is concluded that at least two parent bodies are likely sources for the basaltic achondrites.

Olsen, Edward J.↗
NASA NTRS1989

Spectral mineralogy of terrestrial planets - Scanning their surfaces remotely

Information on the surface mineralogy, chemical composition, and lithology of terrestrial planets, as well as on their atmospheres, that can be obtained by earth-based from visible and NIR spectra of light reflected from planetary surfaces is discussed. Such reflectance spectra may have absorption bands in the 1- and 2-micron wavelength regions which originate from crystal field transitions within Fe(2+) ions. Since pyroxenes with Fe(2+) in M2 positions usually dominate the spectra, the resulting 1-micron vs 2-micron spectral determinative curves can be used to identify compositions and structural types of pyroxenes on the surface of a planet or an asteroid. Future spececraft missions to solar system objects will concentrate on remote-sensing experiments using visible and NIR reflectance spectra. These include the Galileo mission to Jupiter; the Mars Orbiter mission to Phoebus; the Comet Rendezvous Asteroid Flyby mission; the Cassini mission to Saturn; the Lunar Geoscience Observer; and the Mars Rover/Sample Return mission.

Burns, Roger G.↗
NASA NTRS1990

Volatile compounds in shergottite and nakhlite meteorites

Shergottites ALHA77005, EETA79001, and Shergotty, and the nakhlite Nakhla are all found to contain oxidized sulfur (sulfate) of preterrestrial origin, In EETA79001, which is composed of three different lithologies, the degree of sulfur oxidation increased from A to C. Significant bulk carbonate was confirmed in Nakhla and trace carbonate was confirmed for EETA79001, all of which seems to be preterrestrial in origin. Chlorine in shergottites and Nakhla is found to covary with oxidized sulfur, whereas carbonate and sulfate are related inversely. Sulfate and carbonate in shergottites and Nakhla were probably formed by aqueous geochemistry in a highly oxidizing environment sometime near the late-stage histories of the rocks that are now represented as meteorites.

Gooding, James L.↗
NASA NTRS1991

Altered spherules of impact melt and associated relic glass from the K/T boundary sediments in Haiti

Partially to wholly altered glass spherules produced by impact-induced shock melting have been found in the K/T boundary sediments of Haiti which also contain grains of shocked quartz. The relic glass has an approximately dacitic composition, and although grossly similar in composition to most previously described tektite glasses, it is slightly enriched in Ca and slightly depleted in Si, suggesting the Haitian glass was produced either from a target with a greater fraction of carbonate and anhydrite lithologies and fewer silicate units than the targets from which most other tektites were produced, and/or from one with a significant mafic component. The composition of the glass can best be reconciled with a continental margin terrane, consistent with studies of shocked mineral phases reported elsewhere. The thickness of the deposit in which the impact spherules occur indicates the source of the ejecta was in the proto-Caribbean region.

Kring, David A.↗
NASA NTRS1991

The subsurface character of Meteor Crater, Arizona, as determined by ground-probing radar

The first results are presented from a ground-probing-radar survey of the subsurface structure of the Meteor Crater (Arizona) and the surrounding ejecta blanket. Five ground-probing radar transects were conducted, including three complete north-south transects of the interior floor of the crater and a partial east-west transect, connecting the three north-south surveys; the fifth transect was exterior to the crater. A number of subsurface dielectric reflectors were identified in both the interior and exterior transects of the Meteor Crater. The depths of most of these reflectors in the interior transects corresponds to lithological boundaries known from previous data from drilling and shaft excavations. However, some of the reflectors, e.g., the horizontal reflectors within the allochthonous breccia lens, were not known from previous work.

Pilon, J. A.↗
NASA NTRS1991

Geologic mapping of northern Lunae Planun, Mars

Lunae Planum is an elevated region east of the Tharsis rise, and ridged plains containing numerous Sacra Dorsa wrinkle ridges, cross-cutting Sacra Fossae grabens, and lobate scarps compose this Martian Plateau. Geologic mapping of the northern Lunae Planum region was undertaken to better understand to emplacement history of the ridge plains, the structural history of deformation, and the periods of fluvial processes that have modified the region. These investigations are important for several reasons: (1) the history of plains emplacement yields information valuable for understanding the evolution of Tharsis volcanism; (2) interpretation of structural deformation has implications on the lithology of the Martian crust; and (3) determining the history and fate of Martian volatiles is dependent upon knowing the periods of outflow activity. A discussion of the findings is presented.

Craddock, Robert A.↗