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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Geochemical and petrological sampling and studies at the first moon base

Strategic sampling appropriate to the first-order lunar base can advance a variety of first-order lunar geochemical and petrological problems. Field observation and collection of samples would be done on the lunar surface, but detailed analysis would be done mainly in terrestrial laboratories. Among the most important areas of investigation for which field observations can be made and samples can be collected at the initial base are regolith studies, studies of mare and highlands stratigraphy, and a search for rare materials such as mantle nodules. Since the range of exploration may be limited to a radius of about 20 km from the first lunar base, locating the base near a mare-highlands boundary would enable the greatest latitude in addressing these problems.

Haskin, L. A.↗
NASA NTRS1986

Petrology and classification of the Garraf, Spain chondrite

Microscopic and electron microprobe studies indicate that the Garraf meteorite is a highly-recrystallized chondrite of petrologic type 6. Olivine (Fa24.7; PMD 1.1) and low-Ca pyroxene (Fs20.9; PMD 1.1) compositions indicate that it belongs to the L-group. Based on contents of noble gases, pervasive fracturing of silicates, common undulose extinction of olivine and plagioclase, and the lack of melt pockets and maskelynite, Garraf is placed into shock facies b. It is concluded that Garraf is a highly recrystallized L6b chondrite that, after recrystallization, was cataclased and comminuted by shock.

Keil, K.↗
NASA NTRS1987

Global petrologic variations of the Moon: A ternary-diagram approach

A ternary-diagram approach is used to show on a single map as much detailed geochemical information concerning petrologic variations within the lunar crust as is possible. The classification map shows the global spatial distributions of end-member compositions, the transitional spatial relations between end-member compositions, and quantitative estimates of relative proportions of each end member at each pixel location within the orbital groundtracks. The use of elemental ratios in this analysis, instead of the commonly used elemental bivariate diagrams, shows geologic information that is otherwise hidden in individual elemental databases.

Davis, Philip A.↗
NASA NTRS1987

Petrology and geochemistry of alkali gabbronorites from lunar breccia 67975

Detailed results of petrologic and compositional studies of three clasts found in thin sections of the Apollo 16 lunar breccia 67975 and of four clasts extracted from the breccia (for instrumental neutron activation analysis) prior to thin sectioning are reported. The alkali gabbronorites of the breccia form two distinct subgroups, magnesian and ferroan. The magnesian gabbronorites are composed of bytownitic plagioclase, hypersthene, augite, a silica mineral, and trace Ba-rich K-feldspar. The ferroan gabbronorites are composed of ternary plagioclase, pigeonite, augite, Ba-rich K-feldspar, and a silica mineral. Trace minerals in both subgroups are apatite, REE-rich whitlockite, and zircon. The magnesian and ferroan alkali gabbronorites appear to have formed by progressive differentiation of the same, or closely related, parent REE-rich magmas.

James, Odette B.↗
NASA NTRS1987

Petrology and precursors of lithic clasts from feldspathic fragmental breccia 67975

Textures and mineral chemistry (by INAA) of five lithic clasts, including both light green and light gray clasts, from feldspathic fragmental breccia 67975 were studied. The presence of five rock types was confirmed: feldspathic microporphyritic melt breccia, metamorphosed mafic-rich melt breccia with zoned and mantled clasts, 'typical' reequilibrated lunar feldspathic granulites with granoblastic texture and homogeneous mineral chemistry, hornfels, and a recrystallized mafic-rich granulite with relict igneous texture and the composition of a ferroan anorthositic norite. The mineralogy and textural data corroborate the grouping of the light green clasts proposed by Lindstrom (1984). However, the light gray clasts do not appear to be coherent in petrologic (or chemical) characteristics; one is a plagioclase-rich, possibly monomict rock with ferroan anorthositic precursor(s), and the other represents a mixture of feldspathic granulite and ferroan anorthositic norite lithologies.

Mcgee, James J.↗
NASA NTRS1987

Petrology of the igneous rocks

Papers published during the 1983-1986 period on the petrology and geochemistry of igneous rocks are discussed, with emphasis on tectonic environment. Consideration is given to oceanic rocks, subdivided into divergent margin suites (mid-ocean ridge basalts, ridge-related seamounts, and back-arc basin basalts) and intraplate suites (oceanic island basalts and nonridge seamounts), and to igneous rocks formed at convergent margins (island arc and continental arc suites), subdivided into volcanic associations and plutonic associations. Other rock groups discussed include continental flood basalts, layered mafic intrusions, continental alkalic associations, komatiites, ophiolites, ash-flow tuffs, anorthosites, and mantle xenoliths.

Mccallum, I. S.↗
NASA NTRS1988

Lunar composition - A geophysical and petrological synthesis

Lunar compositional constraints are derived on the basis of geophysical data (in particular, the lunar seismic model as revised by Nakamura) and petrological arguments. Only in the case of extreme assumptions can critical aspects of bulk lunar composition be demonstrated to be equivalent to the present-day terrestrial mantle; specifically, the moon has an Mg number that is too low and an alumina abundance that is too high. Over a broad range of crustal densities the presence of a metallic core at least 150 km in radius is necessary to reconcile the upper mantle lunar seismic model with mass and moment of inertia constraints. A significant seismic discontinuity at 500 km depth may mark the lowest extent of early lunar differentiation, possibly representing a transition between highly fractionated upper mantle and less fractionated, perhaps even primordial, middle/lower mantle.

Mueller, Steve↗
NASA NTRS1988

Petrology of brecciated ferroan noritic anorthosite 67215

A petrologic study of breccia 67215 is presented, showing that the rock has the bulk composition of a ferroan noritic anorthosite and is a polymict breccia containing several lithic clast types within a crushed, cataclastic matrix. The dominant lithic clasts contained in breccia 67215 are found to be igneous and metamorphic low- and high- Ca pyroxenes and olivine. Other clasts include granulated and sheared clasts, coarse-grained anorthosite with relatively Fe-rich augite, aphanitic, feldspathic microporphyritic melt breccias, and an impact-melt rock with strongly zoned relatively Mg-rich pyroxene. It is concluded that this rock type is relatively common in the highlands regolith excavated by the North Ray Crater.

Mcgee, James J.↗
NASA NTRS1988

Chemistry and petrology of the Apennine Front, Apollo 15. I - KREEP basalts and plutonic rocks. II - Impact melt rocks

The mineralogy, petrology, and chemistry of rock fragments for the Apennine Front coarse fines (10-4 and 4-2 mm) have been determined. The data are consistent with a single eruptive event that produced several flows. It is found that most of the plutonic rocks are ferroan in nature, with a few belonging to the Mg-suite. The mineral and bulk chemistry of KREEP basalts and the composition of ferroan anorthosites are discussed. Petrographic studies of 21 impact melts are also presented, showing a variety of textures. It is found that the Apollo 15 impact melts are mixtures of low-K Fra Mauro, KREEP, and plutonic components. The Ni/Ir ratios of the melt rocks are shown to be greater than chondritic values, indicating ancient and/or iron meteorite components.

Simon, S. B.↗
NASA NTRS1988

Planet Alsioff - A problem set for students of phase equilibria or metamorphic petrology

This paper presents a problem set that contains questions for students of phase equilibria or metamorphic petrology concerning a hypothetical planet Alsioff, for which incomplete data are given. On this panet, the SiF4 is the major volatile and Al, Si, O, and F are the only elements present. Progressive metamorphism on Alsioff mainly involves devolatilization of fluid SiF4. The problem set includes ten questions. Some of these are concerned with possible chemical reactions that should affect water, wollastonite, or Ca-SiO3 exposed to the atmosphere of Alsioff; the mechanism of controls of the O2 and F2 contents of the Alsioffian atmosphere; and the devolatilization reactions involving SiF4 with progressive thermal metamorphism.

Burt, Donald M.↗
NASA NTRS1989

Millimeter petrology and kilometer mineralogical exploration of the moon

Coordinated petrologic and spectroscopic analyses were undertaken for a specially prepared 1-cm chip of regolith breccia 60019. The mafic minerals of each large clast were readily identified from spectral reflectance measurements of the same clasts, and mineral abundance was shown to be directly related to absorption strength. Although most clasts of 60019 are noritic in composition, the presence of abundant olivine and/or high-Ca pyroxene in several clasts is easily noted spectroscopically. The origin of an unusual absorption feature near 0.6 micron in an anorthositic clast was determined by petrographic analysis to be due to very fine-grained translucent ilmenite. The 60019 matrix is dark and glassy, and although a variety of clasts occur on all scales, particulate powders of 60019 are all very similar and have spectral properties that indicate a noritic breccia bulk composition.

Pieters, C. M.↗
NASA NTRS1989

Petrology and thermal history of type IA chondrules in the Semarkona (LL3.0) chondrite

Detailed petrologic studies have been made of 15 type IA, Fe-poor, porphyritic olivine chondrules in Semarkona (LL3.0). Major and minor element concentrations in olivines, pyroxenes, and mesostases, and bulk composition so the chondrules are measured along with zoning profiles in the olivine and pyroxene crystals. The mineral compositions and textures are best interpreted in terms of closed system crystallization in which the olivines and pyroxenes crystallized in situ from a melt corresponding to the bulk composition of the chondrule. Relict olivine grains are not found in the chondrules. Crystallization probably occurred at a cooling rate of the order of 1000 C/hr. Precursor materials of the chondrules were composed of two components, one refractory Ca-, Al-, and Ti-rich, and one less refractory Si-, Fe-, Cr-, and Mn-rich. The evidence is consistent with Semarkona being one of the least metamorphosed ordinary chondrites.

Jones, R. H.↗
NASA NTRS1990

Petrology and chemistry of Apollo 17 regolith breccias - A history of mixing of highland and mare regolith

Results are presented of petrological and chemical analyses of ten Apollo 17 breccias, showing that two of these consist predominantly of highland material, seven are mare-dominated, and one is a welded volcanic glass deposit; all were formed at or near the Apollo 17 site, and all contain both mare and highland components. The data are indicative of the Apollo 17 breccias formation from immature source regolith. The breccias are considered to be formed locally after an eruption of basalt and orange glass at the site. Since the formation of the breccias, the regolith at the Apollo 17 site has become more mature, and the orange glass abundance has been somewhat decreased by mixing. One of the sample may contain a previously unreported volcanic glass type.

Simon, S. B.↗
NASA NTRS1990

Petrology and mineralogy of Type II, FeO-rich chondrules in Semarkona (LL3.0) - Origin by closed-system fractional crystallization, with evidence for supercooling

The petrology of type II porphyritic olivine chondrules in Semarkona (LL3.0) has been studied in detail. Olivines in these chondrules are euhedral, Fe-rich, and are strongly zoned from cores to rims of grains in FeO (Fa10-30), Cr2O3 (0.2-0.6 wt pct), MnO (0.2-0.7 wt pct), and CaO (0.1-0.4 wt pct). Interstitial mesostasis is rich in Si, Al, and Ca and is glassy with abundant microcrystallites. Minor minerals include troilite, Fe,Ni metal, and chromite. Some olivine grains contain euhedral, fayalite-rich cores that are probably produced during initial supercooling of the chondrule melt. Rare relict grains of forsteritic olivine have compositions very similar to olivines in type IA chondrules in Semarkona and may result from disaggregation of such chondrules. Apart from these relics, all properties of type II chondrules can be described by closed-system fractional crystallization of droplets which were essentially entirely molten. Type IA chondrules may have formed from type II chondrules by loss of Fe and volatiles. Alternatively, the two chondrule types may have formed in regions of considerable diversity in the solar nebula from precursor materials with different Fe/Mg ratios.

Jones, Rhian H.↗
NASA NTRS1990

Distribution of terrestrial age and petrologic type of meteorites from western Libya

A group of 54 meteorites have been recovered from Daraj, Western Libya. After assessment of pairing of samples, using petrologic criteria, C-14 terrestrial ages were obtained on 13 samples selected from 9 different fall events. Eleven of the ages range from 3500 to 7600 years, with only two samples having ages in excess of 10,000 years. The cutoff in ages may be related to the timing of climatic changes in the Hammadah al Hamra.

Jull, A. J. T.↗
NASA NTRS1990

Magnetic petrology of eastern North America diabases. I - Olivine-normative dikes from western South Carolina

The oxide mineralogy and the magnetic behavior of 15 olivine-normative samples obtained from South-Caroline diabase dikes were investigated using electron microprobe and SEM analyses and measurements of natural remanence magnetization (NRM), saturation isothermal remanence magnetization (SIRM), and anhysteritic remanence magnetization. It was found that chromite (which for these olivine-normative diabases is a sensitive petrologic indicator) constitutes up to 0.5 vol pct and that its abundance and composition correlate with bulk rock Cr. Microscopic analyses showed that titanomagnetite compositions were mostly between 0.4 and 0.55. The values of NRM and the NRM/SIRM ratios varied between 4 and 0.01 A sq m/kg and 0.0019 and 0.032, respectively. These properties inversely correlate with Cr content and demonstrably contrast Cr-rich and Cr-poor samples.

Warner, Richard D.↗
NASA NTRS1991

Lunar ferroan anorthosite 60025 - Petrology and chemistry of mafic lithologies

Eleven splits from the mafic-mineral-rich part of anorthosite 60025 were studied in order to establish the exact nature and causes of compositional variations in the minerals of lunar ferroan anorthosites. All splits were analyzed by INAA, and five were studied intensively by petrologic techniques. All splits were found to have similar cataclastic textures and show textural evidence of at least two episodes of deformation. The whole-rock split contains mafic minerals having a wide range of compositions and is probably polymict. It is suggested that the rare-earth patterns for all splits can be duplicated safactorily, assuming that the equilibrium liquids had flat, or nearly flat, chondrite-normalized rare-earth patterns. The plagioclases in all splits were found to be identical. Data obtained indicate that in ferroan anorthosites An content in plagioclase and mg' of associated mafic minerals are not strongly correlated.

James, O. B.↗
NASA NTRS1993

Petrologic study of the Belgica 7904 carbonaceous chondrite - Hydrous alteration, oxygen isotopes, and relationship to CM and CI chondrites

The genetic relationships between the petrology, hydration reactions, and isotopic oxygen composition in the Belgica 7904 (B7904) carbonaceous chondrite, and the relationship between B7904 and the CM and CI chondrites were investigated by characterizing seven components separated from B7904. The seven specimens included two partially altered chondrules, two phylosilicate clasts, two olivine fragments, and one matrix sample. The results of the analyses and thermodynamic calculations suggest that CI chondrites may have been produced in a two-stage alteration process from materials similar to that of the B7904 matrix, by reactions with liquid water in their parent body. The common CM chondrites may have undergone aqueous alteration in the parent body, in addition to hydration in the nebula, resulting in two-stage alterations; the parent body may have been different from that of B7904.

Ikeda, Y.↗