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At least 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Rock 14318 - A polymict lunar breccia with chondritic texture

Rock 14318 is a complex microbreccia consisting of lithic fragments, chondrules, glass spherules, and glass and mineral fragments that are embedded into a fine-grained, partly glassy matrix. Compositions of lithic fragments, glasses and chondrules, in terms of compositional rock and rock suite equivalents, represent members of the ANT (anorthositic-noritic-troctolite) suite; the alkalic high-alumina basalt (KREEP) group; high-alkali quartz basalt; basalt; and dunite. The polymict nature of many lithic fragments suggests that rock 14318 requires at least two, and probably more, impact episodes for its formation. Final agglomeration took place while part of the material was hot, as is indicated by the welded texture, suggesting that the final impact event was a large one, producing a fiery cloud similar to a nuee ardente. The close similarity in texture of lunar rock 14318 to certain polymict-brecciated meteorites such as Siena suggests that meteorites of this type were also formed by complex and successive impact events on the surface of the meteorite parent body, rather than during agglomeration of the parent body.

Kurat, G.↗
NASA NTRS1974

Progress of the LASL dry hot rock geothermal energy project

The possibilities and problems of extracting energy from geothermal reservoirs which do not spontaneously yield useful amounts of steam or hot water are discussed. The system for accomplishing this which is being developed first is a pressurized-water circulation loop intended for use in relatively impermeable hot rock. It will consist of two holes connected through the hot rock by a very large hydraulic fracture and connected at the surface through the primary heat exchanger of an energy utilization system. Preliminary experiments in a hole 2576 ft (0.7852 km) deep, extending about 470 ft (143 m) into the Precambrian basement rock underlying the Jemez Plateau of north-central New Mexico, revealed no unexpected difficulties in drilling or hydraulically fracturing such rock at a temperature of approximately 100 C, and demonstrated a permeability low enough so that it appeared probable that pressurized water could be contained by the basement rock. Similar experiments are in progress in a second hole, now 6701 ft (2.043 km) deep, about 1.5 miles (2.4 km) south of the first one.

Smith, M. C.↗
NASA NTRS1976

Rock failure analysis by combined thermal weakening and water jet impact

The influence of preheating on the initiation of fracture in rocks subjected to the impingement of a continuous water jet is studied. Preheating the rock is assumed to degrade its mechanical properties and strength in accordance with existing experimental data. The water jet is assumed to place a quasi-static loading on the surface of the rock. The loading is approximated by elementary functions which permit analytic computation of the induced stresses in a rock half-space. The resulting stresses are subsequently coupled with the Griffith criteria for tensile failure to estimate the change, due to heating, in the critical stagnation pressure and velocity of the water jet required to cause failure in the rock.

Nayfeh, A. H.↗
NASA NTRS1977

A survey of lunar rock types and comparison of the crusts of earth and moon

The principal known types of lunar rocks are briefly reviewed, and their chemical relationships discussed. In the suite of low-KREEP highland rocks, Fe/(Fe + Mg) in the normative mafic minerals increases and the albite content of normative plagio-clase decreases as the total amount of normative plagioclase increases, the opposite of the trend predicted by the Bowen reaction principle. The distribution of compositions of rocks from terrestrial layered mafic intrusives is substantially different: here the analyses fall in several discrete clusters (anorthositic rocks, norites, granophyres and ferrogabbros, ultramafics), and the chemical trends noted above are not reproduced. It is suggested that the observed trends in lunar highland rocks could be produced by crystal fractionation in a deep global surface magma system if (1) plagiociase tended to float, upon crystallization, and (2) the magma was kept agitated and well mixed (probably by thermal convection) until crystallization was far advanced and relatively little residual liquid was left. After the crustal system solidified, but before extensive cooling had developed a thick, strong lithosphere, mantle convection was able to draw portions of the lunar anorthositic crust down into the mantle.

Wood, J. A.↗
NASA NTRS1978

The lunar highland melt-rock suite

Size can be used as a criterion to select 18 large (larger than 1 cm) samples from among 148 melt-rock fragments of all sizes. This selection provides a suite of large samples which represent the important chemical variants among highland melt rocks; each large sample has enough material for a number of sample-destructive studies, as well as for future reference. Cluster analysis of the total data base of 148 highland melt rocks shows six distinct groups: anorthosite, gabbroic anorthosite, anorthositic gabbro ('highland basalt'), low K Fra Mauro, intermediate-K Fra Mauro, and high-K. Large samples are available for four of the melt-rock groups (gabbroic anorthosite, anorthositic gabbro, low-K Fra Mauro, and intermediate-K Fra Mauro). This sample selection reveals two subgroups of anorthositic gabbro (one anorthite-poor with negative Eu anomaly and one anorthite-rich without Eu anomaly). There is a sharp distinction between those Apollo 16 melt rocks and glasses which have both been classified as 'gabbroic anorthosite'.

Vaniman, D. T.↗
NASA NTRS1979

Pitted and fluted rocks in the Western Desert of Egypt - Viking comparisons

The Western Desert of Egypt is one of the most arid regions on earth and is probably the closest terrestrial analog to the surface of Mars. An expedition to the area in 1978 revealed an abundance of quartzite and basalt rocks that have been pitted and fluted by wind erosion and deflation of the desert surface. These pitted rocks are internally homogeneous, show no internal holes or vesicles, and are considered an important but neglected type of ventifact. They bear a striking resemblance to the pitted and fluted rocks seen by the Viking Landers, rocks that have generally been interpreted as vesicular basalts only slightly modified by wind erosion. Wind tunnel studies of the air flow over and around nonstreamlined hand specimens from the Western Desert show that windward abrasion coupled with negative flow, secondary flow, and vorticity in a unidirectional wind can explain the complex arrays of pits and flutes. These field and laboratory observations suggest that the pitted rocks at the Viking Lander sites are also ventifacts, and thus the Martian surface may be far more wind eroded than previously thought.

Mccauley, J. F.↗
NASA NTRS1980

Spectral reflectance and discrimination of plutonic rocks in the 0.45- to 2.45-micron region

Visible and near-infrared field spectral reflectance measurements of plutonic rocks were acquired in the 0.45- to 2.45-micron region with a portable field reflectance spectrometer. These spectra were used to determine spectral signatures for the various rock types and to evaluate the separability of these rocks based on their spectral characteristics. A total of 135 samples were divided into 11 groups based on their mineralogy. These 11 groups approximately correspond to traditional rock classifications and include five granitic groups, three gabbroic groups, and three ultramafic groups. The positions, intensity, and presence of iron, CO3(-2), and Al-OH and Mg-OH absorption bands varied among the 11 groups. Each rock group also had a range of albedos characteristic of the group. Stepwise linear discriminant analysis was performed on the spectral data to determine the separability of the 11 groups. Classification accuracy for 30 equally spaced wavelength bands between 0.45 and 2.45 microns was 78% with 10% serious misclassifications. The same analysis was repeated, limiting the spectral data to the wavelength regions corresponding to the proposed Landsat D thematic mapper scanner.

Blom, R. G.↗
NASA NTRS1981

Characterization of rock populations on planetary surfaces - Techniques and a preliminary analysis of Mars and Venus

A data collection and analysis scheme developed for the interpretation of rock morphology from lander images is reviewed with emphasis on rock population characterization techniques. Data analysis techniques are also discussed in the context of identifying key characteristics of a rock that place it in a single category with similar rocks. Actual rock characteristics observed from Viking and Venera lander imagery are summarized. Finally, some speculations regarding the block fields on Mars and Venus are presented.

Garvin, J. B.↗
NASA NTRS1985

Study of the physical properties of crystalline rocks in the southeast Voronezh anteclise

The physical properties of rocks, in the crystalline mass of the Voronezh anteclise, were studied. The study of the physical properties of rocks is important for the improvement of geophysical methods for mapping crystalline rocks in the foundation and exploration of different geological objects which are associated with the crystalline foundation, covered by the sedimentary mantle. It is found that: (1) rocks in the crystalline foundation are very different in physical properties; (2) the physical properties are closely related to their substance composition and genesis; (3) petrographic properties give clues of rock afficiation to certain complexes; and (4) physical and magnetic properties should be examined by petrography, chemical and X-ray analysis.

Dmitriyevskiy, V. S.↗
NASA NTRS1984

Alkali gabbronorite, ultra-KREEPy melt rock and the diverse suite of clasts in North Ray crater feldspathic fragmental breccia 67975

Lunar breccia 67975 is a feldspathic fragmental breccia from North Ray crater, Apollo 16. It contains clasts of alkali gabbronorite and ultra-KREEPy mafic fragment-laden melt breccias, which are unique among Apollo 16 samples. Both are alkali- and iron-rich rocks with moderate to high REE concentrations. They more strongly resemble Apollo 14 gabbronorites and alkali anorthosites and KREEP-rich rocks than they do other Apollo 16 samples. The other clasts in 67975 are the ferroan anorthosites, feldspathic melt rocks, and magnesian granulites, which are typical of other feldspathic fragmental breccias. Examination of bulk and mineral compositions of other breccias and melt rocks suggests that alkali gabbronorite may be a minor component in other North Ray crater breccias and feldspathic melt rocks. This implies that alkali gabbronorite was a fairly early (4.0 b.y.) crustal component in the North Ray crater region.

Lindstrom, M. M.↗
NASA NTRS1986

Extensional tectonics during the igneous emplacement of the mafic-ultramafic rocks of the Barberton greenstone belt

The simatic rocks (Onverwacht Group) of the Barberton greenstone belt are part of the Jamestown ophiolite complex. This ophiolite, together with its thick sedimentary cover occupies a complex thrust belt. Field studies have identified two types of early faults which are entirely confined to the simatic rocks and are deformed by the later thrusts and associated folds. The first type of fault (F1a) is regional and always occurs in the simatic rocks along and parallel to the lower contacts of the ophiolite-related cherts (Middle Marker and equivalent layers). These fault zones have previously been referred to both as flaser-banded gneisses and as weathering horizons. In general the zones range between 1-30m in thickness. Displacements along these zones are difficult to estimate, but may be in the order of 1-100 km. The structures indicate that the faults formed close to horizontal, during extensional shear and were therefore low angle normal faults. F1a zones overlap in age with the formation of the ophiolite complex. The second type of faults (F1b) are vertical brittle-ductile shear zones, which crosscut the complex at variable angles and cannot always be traced from plutonic to overlying extrusive (pillowed) simatic rocks. F1b zones are also apparently of penecontemporaneous origin with the intrusive-extrusive igneous processs. F1b zones may either represent transform fault-type activity or represent root zones (steepened extensions) of F1a zones. Both fault types indicate extensive deformation in the rocks of the greenstone belt prior to compressional overthrust tectonics.

Dewit, M. J.↗
NASA NTRS1988

Nature and origin of mineral coatings on volcanic rocks of the Black Mountain, Stonewall Mountain, and Kane Springs Wash volcanic centers, Southern Nevada

Comparative lab spectra and Thematic Mapper imagery investigations at 3 Tertiary calderas in southern Nevada indicate that desert varnish is absorbant relative to underlying host rocks below about 0.7 to 1.3 microns, depending on mafic affinity of the sample, but less absorbant than mafic host rocks at higher wavelengths. Desert varnish occurs chiefly as thin impregnating films. Distribution of significant varnish accumulations is sparse and localized, occurring chiefly in surface recesses. These relationships result in the longer wavelength bands and high 5/2 values over felsic units with extensive desert varnish coatings. These lithologic, petrochemical, and desert varnish controlled spectral responses lead to characteristic TM band relationships which tend to correlate with conventionally mappable geologic formations. The concept of a Rock-Varnish Index (RVI) is introduced to help distinguish rocks with a potentially detectable varnish. Felsic rocks have a high RVI, and those with extensive desert varnish behave differently, spectrally, from those without extensive varnish. The spectrally distinctive volcanic formations at Stonewall Mountain provide excellent statistical class segregation on supervised classification images. A binary decision rule flow-diagram is presented to aid TM imagery analysis over volcanic terrane in semi-arid environments.

Taranik, James V.↗
NASA NTRS1988

Microdeformation in Vredefort rocks; evidence for shock metamorphism

Planar microdeformations in quartz from basement or collar rocks of the Vredefort Dome have been cited for years as the main microtextural evidence for shock metamorphism in this structure. In addition, Schreyer describes feldspar recrystallization in rocks from the center of the Dome as the result of transformation of diaplectic glass, and Lilly reported the sighting of mosaicism in quartz. These textural observations are widely believed to indicate either an impact or an internally produced shock origin for the Vredefort Dome. Two types of (mostly sub) planar microdeformations are displayed in quartz grains from Vredefort rocks: (1) fluid inclusion trails, and (2) straight optical discontinuities that sometimes resemble lamellae. Both types occur as single features or as single or multiple sets in quartz grains. Besides qualitative descriptions of cleavage and recrystallization in feldspar and kinkbands in mica, no further microtextural evidence for shock metamorphism at Vredefort has been reported to date. Some 150 thin sections of Vredefort basement rocks were re-examined for potential shock and other deformation effects in all rock-forming minerals. This included petrographic study of two drill cores from the immediate vicinity of the center of the Dome. Observations recorded throughout the granitic core are given along with conclusions.

Reimold, W. U.↗
NASA NTRS1991

Rock fraction effects on the interpretation of microwave emission from soils

The effects of rock fraction on the relationship between microwave emission and surface soil moisture were investigated through a combination of laboratory dielectric measurements and field observation of emissivity. Field measurements were conducted which included soils with and without rocks. Microwave brightness temperature was measured at L and C band using a truck-mounted radiometer. Dielectric measurements were made at L band. Field observations of emissivity showed that the presence of rocks decreases the range of the measurements. At 21 cm this decrease was relatively small; however, at 6 cm almost all sensitivity to soil moisture was eliminated by the presence of 35 percent rocks. Comparisons between observed and predicted data showed that the effects of rock fraction are not significant in estimating the sample soil moisture for the tested conditions.

Jackson, Thomas J.↗
NASA NTRS1992

Rock fraction effects on the interpretation of microwave emission from soils

The effect of the rock fraction of soil on emissivity is presently investigated through a combination of laboratory dielectric measurements and field observation of emissivity from soils with and without rocks. The rock fraction reduced the range of emissivity; beyond this, it appears to be important only in determining the moisture in the soil component. Data gathered at 6 cm indicate that the presence of rocks renders this and shorter wavelengths useless as soil-moisture sensors. Modeling of the 21-cm case suggest that rock-fraction effects on soil dielectric properties can be compensated for by the greater surface roughness.

Jackson, Thomas J.↗
NASA NTRS1993

Melt rock components in KREEPy breccia 15205: Petrography and mineral chemistry of KREEP basalts and quartz-normative mare basalts

Many current models for the origin of lunar highland rocks feature as an essential component the assimilation of KREEPy material by primitive magmas parental to the Mg-rich suite and alkali suite plutonic rocks. Similar models have also been proposed for the origin of various mare basalt suites. However, any model which considers assimilation of KREEP an important petrologic process must sooner-or-later deal with the question: what is KREEP? Because pristine KREEP basalts are rare, and most known samples are small (e.g., 15382/15386), the geochemical variability of KREEP basalts is poorly known. Other KREEP compositions which are commonly used in these models include the hypothetical 'high-K KREEP' component of Warren and Wasson, which is derived from Apollo 14 soil data, and the 'superKREEP' quartz-monzodiorite 15405. Lunar breccia 15205 is a polymict regolith breccia that consists of approximately 20% KREEP basalt clasts and 20% quartz-normative basalt clasts in a KREEP-rich matrix. Bulk rock mixing calculations show that this sample comprises about 84% KREEP. The clasts range up to 1 cm in size, but most are considerably smaller. The primary aim is to characterize pristine KREEP basalts petrographically, to establish the range in chemical compositions of KREEP basalts, and to test models that were proposed for their origin. In addition, we may be able to extend the compositional range recognized in the quartz-normative basalt suite and cast some light on its origin as well. Preliminary whole rock geochemical data on the KREEP basalts are presented in a companion paper by M.M. Lindstrom and co-workers. Concentration is on petrography and mineral chemistry of these clasts, and the implications these data have for the origin of the different melt rock suites.

Shervais, John W.↗
NASA NTRS1995

Processes involved in the formation of magnesian-suite plutonic rocks from the highlands of the Earth's Moon

The earliest evolution of the Moon likely included the formation of a magma ocean and the subsequent development of anorthositic flotation cumulates. This primary anorthositic crust was then intruded by mafic magmas which crystallized to form the lunar highlands magnesian suite. The present study is a compilation of petrologic, mineral-chemical, and geochemical information on all pristine magnesian-suite plutonic rocks and the interpretation of this data in light of 18 'new' samples. Of these 18 clasts taken from Apollo 14 breccias, 12 are probably pristine and include four dunites, two norites, four troctolites, and two anorthosites. Radiogenic isotopic whole rock data also are reported for one of the 'probably pristine' anorthositic troctolites, sample 14303,347. The relatively low Rb content and high Sm and Nd abundances of 14303,347 suggest that this cumulate rock was derived from a parental magma which had these chemical characteristics. Trace element, isotopic, and mineral-chemical data are used to interpret the total highlands magnesian suite as crustal precipitates of a primitive KREEP (possessing a K-, rare earth element (REE)-, and P-enriched chemical signature) basalt magma. This KREEP basalt was created by the mixing of ascending ultramafic melts from the lunar interior with urKREEP (the late, K-, REE-, and P-enriched residuum of the lunar magma ocean). A few samples of the magnesian suite with extremely elevated large-ion lithophile elements (5-10x other magnesian-suite rocks) cannot be explained by this model or any other model of autometasomatism, equilibrium crystallization, or 'local melt-pocket equilibrium' without recourse to an extremely large-ion lithophile element-enriched parent liquid. It is difficult to generate parental liquids which are 2-4 x higher in the REE than average lunar KREEP, unless the liquids are the basic complement of a liquid-liquid pair, i.e., the so-called 'REEP-fraction,' from the silicate liquid immiscibility of urKREEP. Scarce age information on lunar rocks suggests that magnesian-suite magmatism was initiated at progressively more recent time from the northeast to the southwest on the lunar nearside from 4.45 to 4.25 Ga.

Snyder, Gregory A.↗
NASA NTRS1994

Evidence for a Meteoritic Component in Impact Melt Rock from the Chicxulub Structure

The Chicxulub structure in Yucatan, Mexico, has recently been recognized as a greater then 200-km-diameter multi-ring impact crater of K-T boundary age. Crystalline impact melt rocks and breccias from within the crater, which have compositions similar to those of normal continental crustal rocks and which show shock metamorphic effects, have been studied for trace element and Re-Os isotope compositions. Re-Os isotope systematics allow the sensitive and selective determination of an extraterrestrial component in impact-derived rocks. A melt rock sample shows elevated iridium concentrations, an osmium concentration of 25 ppb, and a low Os-187/Os-188 ratio of 0.113, which are incompatible with derivation from the continental crust. Even though the Os-187/Os-188 ratio is slightly lower than the range so far measured in meteorites, a mantle origin seems unlikely for mass balance reasons and because the cratering event is unlikely to have excavated mantle material. The data support the hypothesis of a heterogeneously distributed meteoritic component in the Chicxulub melt rock. A sample of impact glass from the Haitian K-T boundary at Beloc yielded about 0.1 ppb osmium and an Os-187/0s-188 ratio of 0.251, indicating the presence of a small meteoritic component in the impact ejecta as well.

Koeberl, Christian↗