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All sourcesNASA NTRSDOE OSTI
NASA NTRS1996

Early Energetic Particle Irradiation of the HED Parent Body Regolith

Previous studies have shown that many individual grains within the dark phase of the Kapoeta howardite were irradiated with energetic particles while residing on the surface of the early HED regolith. Particle tracks in these grains vary in density by more than an order of magnitude and undoubtedly were formed by energetic heavy (Fe) ions associated with early solar flares. Early Irradiation of HED Regolith: Concentrations of excess Ne alone are not sufficient to decide between competing galactic and solar irradiation models. However, from recent studies of depth samples of oriented lunar rocks, we have shown that the cosmogenic 21-Ne/22-Ne ratio produced in feldspar differs substantially between Galactic Cosmic Radiation (GCR) and solar protons, and that this difference is exactly that predicted from cross-section data. Using Ne literature data and new isotopic data we obtained on acid-etched, separated feldspar from both the light and dark phases of Kapoeta, we derive 21-Ne/22-Ne = 0.80 for the recent GCR irradiation and 21-Ne/22-Ne = 0.68 for the early regolith irradiation. This derived ratio indicates that the early Ne production in the regolith occurred by both galactic and solar protons. If we adopt a likely one-component regolith model in which all grains were exposed to galactic protons but individual grains had variable exposure to solar protons, we estimate that this early GCR irradiation lasted for about 3-6 m.y. More complex two-component regolith models involving separate solar and galactic irradiation would permit this GCR age to be longer. Higher-energy solar protons would permit the GCR to be longer. Higher-energy solar protons would permit the GCR age to be shorter. Further, cosmogenic 126(Xe) in Kapoeta dark is no more than a factor of about 2 higher than that observed in Kapoeta light. Because 126(Xe) can only be formed by galactic protons and not solar protons, these data support a short GCR irradiation for the HED regolith. This would also be the maximum time peRiod for the solar irradiation. Various asteroidal regolith models, based on Monte Carlo modeling of impact rates as a function of size and on irradiation features of meteorites, predict surface exposure times of about 0.1 to 10 m.y., and depend on such factors as gravity, rock mechanical properties, and micrometeoroid flux. Because the depth at which solar Fe tracks are produced (is much less than 1 micrometer) is much less than the depth at which Solar Cosmic Rays (SCR) Ne is produced (about 1 cm), for a reasonably well-stirred HED regolith the "surface exposure time" for SCR 21-Ne production should be significantly longer than that for solar tracks and some other surface irradiation features. Enhanced Solar Proton Irradiation: For bulk samples of Kapoeta dark feldspar and a one-component regolith model, the derived ratio of 21-Ne/22-Ne = 0.68 implies that the early production ratio of SCR 21-Ne to GCR 21-Ne was about 0.5-1.5. This ratio is independent of any assumptions about the fraction of dark grains that are irradiated or of the variability in the degree of solar irradiation among grains. The 21-Ne SCR/GCR ratio indirectly derived from bulk Kapoeta pyroxene is somewhat larger, as is the ratio derived for simple two-component regolith models. Individual feldspar grains that were extensively solar irradiated would require even larger 21-Ne SCR/GCR production ratios. In contrast, the theoretical SCR/GCR production ratio for lunar feldspar with 0 g/CM2 shield ing is is less than or equal to 2, and the lowest ratio observed in near-surface samples of lunar anorthosites is less than or equal to 1. Considering the greater solar distance of Vesta (compared to the Moon), the likelihood that SCR 21-Ne was acquired under some shielding where production rates are lower, and the likelihood that the exposure time to galactic protons exceeded the exposure time to solar protons because of their very different penetration depths, the 21-Ne SCR/GCR production ratio on the HED parent body was probably < 0.1. The relatively large difference between the derived 21-Ne SCR/GCR ratio in Kapoeta dark feldspar and the estimated production ratio strongly indicates that the early solar irradiation involved a flux -20-50x the recent solar flux. This enhanced proton flux was probably associated with an overall greater solar activity in the first approximately 10(exp 7) to 10(exp 8) years of solar history.

Bogard, D. D.↗
DOE OSTI2024

Compositional zoning of the Otowi Member of the Bandelier Tuff, Valles caldera, New Mexico, USA

The Otowi Member of the Bandelier Tuff erupted at ca. 1.60 Ma from the Valles caldera (New Mexico, USA). It consists of as much as 400 km 3 (dense rock equivalent) of strongly differentiated high-silica rhyolite and shows systematic upward variations in crystallinity, mineral chemistry, and trace element concentrations through its thickness, but the major element composition is almost constant and is near the low-pressure granite minimum. Incompatible trace elements in whole pumice fragments and glasses show well-correlated linear covariations. Upward zoning to lower abundances of incompatible trace elements is accompanied by development of overgrowths on quartz and alkali feldspar, although earlier-formed interiors of quartz and feldspar have near-constant compositions throughout the tuff, modified by cation diffusion in the case of feldspar. Melt inclusions in remnant quartz cores show diverse Pb isotope ratios, pointing to a wide range of distinct protoliths that contributed rhyolitic melt to the Otowi magma. Mineral thermometers suggest a modest temperature gradient through the melt body, perhaps of 40 °C, at the time of eruption. Chemical, textural, and mineralogical variations and volume-composition relations through the tuff are consistent with an origin for zoning by melting of a high-crystallinity cumulate layer beneath cognate supernatant liquid to produce denser, remobilized liquid of accumulative composition (i.e., the “modified mush model”). Melting may have occurred in several episodes. The latest of these episodes, probably thousands of years prior to eruption, introduced new rhyolitic liquid into the system and was associated with a thermal excursion, recorded in core compositions of pyroxene, during which much of the earlier crystal mass was dissolved. This left inherited cores and interiors of accumulated quartz and feldspar mantled with new growth having less-evolved compositions (higher Ti, Sr, and Ba). Changing solubility of zircon during cumulate melting produced a reversal of Zr concentrations. There is no clear petrologic evidence of a recharge eruption trigger; nonetheless, compositional zoning resulted mainly from repeated recharge-induced remobilization of quartz-feldspar cumulate. The Otowi system was built, evolved, and modified by several events over the course of a few hundred thousand years.

Wolff, J. A.↗
NASA NTRS1996

The Cooling History and Structure of the Ordinary Chondrite Parent Bodies

Most major meteorite classes exhibit significant ranges of metamorphism. The effects of metamorphism have been extensively characterized, but the heat source(s) and the metamorphic environment are unknown. Proposed beat sources include Al-26, Fe-60, electromagnetic induction, and impact. It is typically assumed that metamorphism occurred in parent bodies of some sort, but it uncertain whether these bodies were highly structured ("onion skins") or were chaotic mixes of material ("rubble piles"). The lack of simple trends of metallographic cooling rates with petrologic type has been considered supportive of both concepts. In this study, we use induced thermoluminescence (TL) as an indicator of thermal history. The TL of ordinary chondrites is produced by sodic feldspar, and the induced TL peak temperature is related to its crystallographic order/disorder. Ordered feldspar has TL peak temperatures of approx. 120 C, and disordered feldspar has TL peak temperatures of approx. 220 C. While ordered feldspar can be easily disordered in the laboratory by heating above 650 C and is easily quenched in the disordered form, producing ordered feldspar requires cooling at geologic cooling rates. We have measured the induced TL properties of 101 equilibrated ordinary chondrites, including 49 H, 29 L, and 23 LL chondrites. For the H chondrites there is an apparent trend of decreasing induced TL peak temperature with increasing petrologic type. H4 chondrites exhibit a tight range of TL peak temperatures, 190 C - 200 C, while H6 chondrites exhibit TL peak temperatures between 180 C and 190 C. H5 chondrites cover the range between H4 and H6, and also extend up to 210 C. Similar results are obtained for LL chondfiles and most L6 chondrites have lower induced TL peak temperatures than L5 chondrites.

Benoit, P. H.↗
NASA NTRS2018

Investigating Variations in Water Abundances in Lunar Felsite Clasts Using Coordinated Field-Emission STEM and NanoSIMS Analyses

As representatives of petrochemically-evolved igneous rocks on the Moon, the granitic felsite clasts in lunar breccias have come under renewed focus as part of new efforts to use feldspars for assessing the inventory of lunar water and other volatiles. Previous petrologic studies of these clasts were tilted towards finding those assemblages and relationships most likely to be direct products of magmatic processes. In support of our on-going NanoSIMS (Nanoscale Secondary Ion Mass Spectrometry) measurements of trace water contents in the feldspars in these clasts, we are using coordinated analytical SEM (Scanning Electron Microscopy), electron probe microanalyzer (EPMA) and analytical field emission scanning transmission electron microscopy (FE-STEM) techniques to re-evaluate the full diversity of processes under which the feldspar-bearing assemblages in these clasts formed. Here we report a comparison of FE-STEM imaging and microanalysis results obtained on focused ion beam (FIB) sections extracted from felsite (alkali feldspar plus SiO2 plus or minus plagioclase) clasts in lunar breccias 15405 and 12013. The feldspars in these clasts have water contents which, although relatively low (7-18 ppm) by terrestrial standards, still show values significantly higher than measurements (approximately 0.5 ppm) of nominally anhydrous NanoSIMS standards.

Christoffersen, Roy↗
DOE OSTI2022

Ca-isotopes as a robust tracer of magmatic differentiation

The large mass difference (~10%) between the two most abundant isotopes of calcium, 40 Ca and 44 Ca, gives Ca great potential in tracking mass-dependent fractionation during magmatic processes. Resolvable Ca-isotope fractionation during fractional crystallization of magma, particularly by feldspar in evolved melts, has been theoretically inferred but not robustly tested in nature. To further explore the effects of magmatic differentiation on Ca-isotope systematics, we studied the late-Permian alkaline igneous suite of the Øyangen Caldera, Oslo Rift, Norway, consisting of volcanic and intrusive units ranging from basanitic to rhyolitic compositions. Major and trace element variations and modeling demonstrate that the main series of samples (N = 21), including basanites, ring-dyke syenites, and central-dome syenites, likely documents a co-genetic and closed-system fractional crystallization sequence. Our data show minimal δ 44/40 Ca variation (< 0.05 ‰) in the intermediate magma and a marked increase in δ 44/40 Ca in the felsic magma of the Øyangen Caldera (from 0.62 ± 0.02 ‰ to 1.15 ± 0.03 ‰ relative to Ca standard, SRM915a). The systematic increase is best explained by equilibrium isotopic fractionation dominated by alkali feldspar in the fractionating mineral assemblage. This is further supported by strong correlations between δ 44/40 Ca, CaO, and Eu/Eu* in the main-series samples. Implementing a Monte Carlo approach, isotopic modeling of the liquid line of descent using Rayleigh fractionation is highly consistent with the observed Ca-isotope evolution. For the first time, we confirm prominent Ca stable isotope fractionation in felsic-stage differentiation of alkaline magma and constrain the isotope fractionation factors of plagioclase and K-feldspar. Integrated with extant estimations on mineral fractionation factors from the literature, our results suggest increasing fractionation effects of rock-forming minerals with decreasing Ca content. Finally, the affirmation of significant Ca-isotope fractionation in alkaline magma by feldspar empowers the application of Ca as a versatile tracer of crustal evolution, allowing further tests in other magmatic conditions across various planetary objects.

58 GEOSCIENCES↗
NASA NTRS1986

Thermoluminescence and Antarctic meteorites

The level of natural thermoluminescence (TL) in meteorites is the result of competition between build-up, due to exposure to cosmic radiation, and thermal decay. Antarctic meteorites tend to have lower natural TL than non-Antarctic meteorites because of their generally larger terrestrial ages. However, since a few observed falls have low TL due to a recent heating event, such as passage within approximately 0.7 astronomical units of the Sun, this could also be the case for some Antarctic meteorites. Dose rate variations due to shielding, heating during atmospheric passage, and anomalous fading also cause natural TL variations, but the effects are either relatively small, occur infrequently, or can be experimentally circumvented. The TL sensitivity of meteorites reflects the abundance and nature of the feldspar. Thus intense shock, which destroys feldspar, causes the TL sensitivity to decrease by 1 to 2 orders of magnitude, while metamorphism, which generates feldspar through the devitrification of glass, causes TL sensitivity to increase by a factor of approximately 10000. The TL-metamorphism relationship is particularly strong for the lowest levels of metamorphism. The order-disorder transformation in feldspar also affect the TL emission characteristics and thus TL provides a means of paleothermometry.

Sears, D. W. G.↗
NASA NTRS1986

A compositional study of the aristarchus region of the moon using near-infrared reflectance spectroscopy

Newly obtained near-infrared reflectance spectra for features on or near the Aristarchus Plateau demonstrate the diversity of compositions in the region. Highland units are of three probable compositions: a feldspar and clinopyroxene assemblage; a probable clinopyroxene, olivine, and possibly feldspar assemblage; and an assemblage composed of olivine or olivine and feldspar. The feldspar-clinopyroxene assemblage is tentatively correlated with the major Th anomaly centered on Aristarchus crater. The regional pyroclastic deposits on the plateau are composed of greater than 90 percent Fe(2+)-bearing glass. The Aristarchus cratering event fully penetrated any mare or pyroclastics in the target. Evidence for mare-related material is found in the ejecta on the mare side of the mare-plateau contact.

Lucey, P. G.↗
NASA NTRS1992

Optical and TEM study of shock metamorphism from the Sedan test site

Thus far, detailed petrologic studies of shock metamorphism have been performed on samples recovered from laboratory experiments and on a few natural impactites. The loading history of these samples is quite different: In particular, laboratory experiments spend only a short time (less than 1 microsec) at peak pressure, whereas natural impactites may have stress pulses from 0.1 - 1 ms. On the other hand, laboratory experiments have known stress histories; natural impactites do not. Natural samples are also subjected to thousands or millions of years of postshock annealing and/or weathering. A useful intermediate case is that of nuclear detonation. Stress pulses for these events can reach 0.1 ms or higher, and samples are obtained in pristine condition. All three types of loading produce stresses of hundreds of kilobars. Samples studied were taken from the Sedan nulcear test site, and consist of a coarse-grained granodiorite containing quartz, K-feldspar, cordierite, and hornblende. Samples were studied optically in this section, then were thinned with an ion mill and studied by transmission electron microscopy (TEM). Optically, quartz and K-feldspar displayed numerous sets of planar deformation features (PDF's) identical to the nondecorated PDF's seen in laboratory samples and many natural impactites. TEM study showed that the PDF's in quartz and feldspar corresponded to densely packed wide transformation lamellae identical to those described in laboratory studies. The transformation lamellae in both minerals were amorphous, with no sign of high-pressure phases. In the case of K-feldspar only, narrow sublamellae extended outward from some wide lamellae. Quartz, which was more abundant and studied more extensively, contained no shock-induced dislocations. Some planar features were also seen in cordierite, but could not be identified due to rapid beam damage. No shock defects were seen in hornblende in TEM. The shock-induced defects present at the Sedan site are very similar to those seen in shock recovery experiments, and also to those present at certain natural events (e.g., Meteor Crater). This suggests that shock deformation in quartz is not strongly dependent on shock pulse duration, and that laboratory recovery experiments are useful simulations of natural impact events.

Gratz, A. J.↗
NASA NTRS1993

Alkali-granitoids as fragments within the ordinary chondrite Adzhi-Bogdo: Evidence for highly fractionated, alkali-granitic liquids on asteroids

Adzhi-Bogdo is an ordinary chondrite regolith breccia (LL3-6) that fell October 30, 1949 in Gobi Altay, Mongolia. The rock consists of submm- to cm-sized fragments embedded in a fine-grained elastic matrix. The breccia contains various types of clasts, some of which must be of foreign heritage. Based on chemical compositions of olivine some components have to be classified as L-type. Components of the breccia include chondrules, impact melts (some are K-rich, similar to those found in other LL-chondrites, highly recrystalized rock fragments ('granulites'), pyroxene-rich fragments with achondritic textures, and alkali-granitoidal fragments that mainly consist of K-feldspar and quartz or tridymite. Probably, this is the first report on granitoids from asteroids. It can be ruled out that these fragments represent huge rock assemblages of the parent body like granites do on Earth. Therefore, to avoid misunderstandings, these rocks will be designated as granitoids. In one thin section four granitoids were observed. The main phases within these clasts are K-feldspar and SiO2-phases. Minor phases include albite, Cl-apatite, whitlockite, ilmenite, zircon, Ca-poor pyroxene, and an unidentified Na,Ti-bearing silicate. Based on chemical composition and on optical properties quartz appears to be the SiO2-phase in two fragments, whereas tridymite seems to occur in the other two. The calculated formula of the unknown Na,Ti-rich silicate is very close to (Na,Ca)2.7(Fe,Mg)6(Ti)1.3(Si)7(O)24. Quartz and K-feldspar can reach sizes of up to 700 microns. Thus, the fragments can be described as coarse-grained (by chondritic standards). This is especially the case considering that quartz and K-feldspar are very rare minerals in ordinary chondrites. Representative analyses of minerals from some granitoidal clasts are given. Based on the mineral compositions and the modal abundances the bulk compositions were calculated. Besides these granitoidal rocks, pyroxene-rich fragments occur that show exsolution textures that are similar to those found in eucrites.

Bischoff, A.↗
NASA NTRS1993

Heterogeneous plagioclase compositions in the Maralinga CK4 chondrite

One of the characteristic features of CK chondrites is the wide compositional range displayed by feldspar grains in matrix relative to the narrow range of compositions exhibited by the highly equilibrated olivines and pyroxenes. Recently, it was suggested that these heterogeneous feldspar compositions may have been strongly influenced by shock metamorphisms. It is shown that the apparent range of feldspar compositions in Maralinga probably results from annealing during parent body thermal metamorphism rather than shock. The majority of matrix feldspars in Maralinga are typically 50 microns in size and are compositionally zoned, with oligoclase cores (approximately An40) and bytownite rims (approximately An80). The contact between core and rim is sharp and abrupt and is readily observed in backscattered scanning electron microscopy (SEM) images.

Keller, Lindsay P.↗
NASA NTRS2016

Cooling History and Redox State of NWA 8694 Chassignite: Comparison with Chassigny and NWA 2737

NWA 8694 is a new chassignite whose constituent minerals are more Fe-rich than those in the other known chassignites (Chassigny and NWA 2737), and may suggest a petrogenetic relationship to nakhlites. In this abstract we report mineralogy of NWA 8694 to infer its cooling rate and redox state, and discuss its thermal and shock history in comparison with other chassignites. NWA 8694 is a cumulate dunite of approximately 2 mm olivine with interstitial pyroxene and feldspar. Olivine is homogeneous (Fo(sub 55-56)), but Ca decreases at the approximately 50-100 micrometer rim (0.25-0.1 wt% CaO). Because the Ca-depleted rim is narrower than those in other chassignites (approximately 50 micrometer), NWA 8694 may have cooled slightly faster than the others (approximately 30 C/yr), but would be in the same order. Pyroxenes are low- and high-Ca pyroxenes, both exhibiting sub-micron exsolution textures (0.2-0.3 micrometer wide lamellae with the spacing of 0.8-1.8 micrometers). Although the low-Ca pyroxene host has an orthopyroxene composition (Wo approximately 2), the EBSD analysis suggests a pigeonite structure (P2(sub 1)/c), which is also reported from the Chassigny pyroxene. The size of exsolution texture is a bit smaller, but broadly similar to those in other chassignites, implying a similar fast cooling rate (35-43 C/yr). Feldspars are isotropic (plagioclase: clustered around An25Or10, K-feldspar: approximately An19Or78), suggestive of extensive shock metamorphism, consistent with undulatory extinction of olivine. Feldspar compositions are around the equilibrium isotherm of approximately 800 C. The olivine and chromite compositions give an equilibration temperature of 760-810 C and logfO2 of QFM+/-0.3. The inferred fast cooling rate and high fO2 of NWA 8694 are both similar to those of Chassigny and NWA 2737, and suggest a common formation condition (e.g., thick lava flow or shallow intrusion) under oxidizing condition. The Fe-rich mineral compositions of NWA 8694 may be due to crystallization from more fractionated melt than the other chassignites. The shock degree of NWA 8694 would be similar to Chassigny, but distinct from NWA 2737 with darkened olivine showing more extensive shock.

Mikouchi, T.↗
NASA NTRS2019

Constraints on Martian Ancient Magmatic Processes Using Mineral Chemistry of Sedimentary Rocks in Gale Crater, Mars

If Mars has been assumed to be mostly basaltic for a long time, a series of recent discoveries have challenged this simplistic view. Orbital data indicated feldspar-rich rocks in Noachian terrains, likely supporting ancient evolved magmatism. The first indurated regolithic martian meteorite breccia NWA 7034, dated at 4.43 Gyr, contain several leucocratic felsic clasts identified as monzonitic and trachyandesitic, containing feldspars including K-spars and Na-rich plagioclases, pyroxenes, ilmenites and apatites. These clasts have been interpreted as the result of crystallization of a large impact pond. The Mars Science Laboratory rover (Curiosity), travelling within sedimentary bedrock on the floor of the Gale impact crater, discovered feldspar cumulates and a trachyandesite suggesting fractional crystallization of a basaltic melt. In addition, in the Bradbury group of fluvio-deltaic rocks (observed during the 1st 750 sols), sedimentary rocks are mostly comprised of secondary phases and detrital igneous minerals like feldspar, and pyroxene that are thought to come from Noachian-aged magmatic sources, although no definite origin and igneous processes have been inferred.

Payr, V.↗
NASA NTRS2020

Corrigendum to: Volatiles in Lunar Felsite Clasts: Impact-related Delivery of Hydrous Material to an Ancient Dry Lunar Crust

Hydrous components were measured in nominally anhydrous minerals, primarily lunar feldspar, and reported by Simon et al. (2020). In the feldspar mineral structure, these components are contained in the form of OH, H2O, and/or NH4+molecules (Johnson, 2006 and references therein). The advantages of the ion microprobe technique employed by Simon et al. (2020) include high spatial resolution, apparent insensitivity to crystal orientation, high precision, and low detection limits, but unlike complementary spectroscopy techniques (i.e., FTIR) they preclude assignment of molecular species(Mosenfelder et al. 2015). Convention in the lunar sample community is to report major elemental abundances and hydrogen as oxides, H2O is the oxide for H. This convention was not followed by Simon et al. (2020), but rather the measured hydrogen component was reported as H to avoid the appearance of assigning the measured hydrogen concentration to a specific molecular species. The speciation of the hydrous component in terrestrial feldspars varies predominantly between OH and H2O, with no apparent correlation to feldspar composition, and only slight correlation to volcanic-to-plutonic igneous rock type (Johnson and Rossman, 2004).

J. I. Simon↗
DOE OSTI2021

Dual microscopy to explore enhanced atmospheric ice nucleation on multi-component aerosols

Using an optical microscopy setup adapted to in-situ studies of ice formation at ambient pressure, we examined a specific multicomponent mineral, microcline, with the ultimate aim of gaining a more realistic understanding of ice nucleation in Earth’s atmosphere. We focused on a perthitic feldspar, microcline, to test the hypothesis that co-existence in some feldspars of K-rich and Na-rich phases are contributing to enhanced ice nucleation. On a sample deliberately chosen to contain lamella, a typical perthitic microstructure, and flat surface regions next to each other, we performed a series of ice formation experiments. We found microcline to promote ice formation, causing a large number of ice nucleation events at around - 27°C. The number of ice nuclei decreased from experimental run to experimental run, indicating surface aging upon repeated exposure to humidity. An analysis of 10 experimental runs of identical conditions did not reveal an obvious enhancement of ice formation at the lamellar microstructure. Instead, we find efficient nucleation at various surface sites that produce orientationally aligned ice crystallites with asymmetric shape. Based on this observation we propose that surface steps running along select directions produce microfacets of an orientation that is favorable to enhanced ice nucleation, similar to previously reported for K-rich feldspars.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Saprotrophic Fungus Induces Microscale Mineral Weathering to Source Potassium in a Carbon-Limited Environment

Plants rely on potassium for many critical biological processes, but most soils are potassium limited. Moving potassium from the inaccessible, mineral-bound pool to a more bioavailable form is crucial for sustainably increasing local potassium concentrations for plant growth and health. Here, we use a synthetic soil habitat (mineral doped micromodels) to study and directly visualize how the saprotrophic fungus, Fusarium sp. DS 682, weathers K-rich soil minerals. After 30 days of fungal growth, both montmorillonite and illite (secondary clays) had formed as surface coatings on primary K-feldspar, biotite, and kaolinite grains. The distribution of montmorillonite differed depending on the proximity to a carbon source, where montmorillonite was found to be associated with K-feldspar closer to the carbon (C) source, which the fungus was inoculated on, but associated with biotite at greater distances from the C source. The distribution of secondary clays is likely due to a change in the type of fungal exuded organic acids; from citric to tartaric acid dominated production with increasing distance from the C source. Thus, the main control on the ability of Fusarium sp. DS 682 to weather K-feldspar is proximity to a C source to produce citric acid via the TCA cycle.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1973

Partial pressures of oxygen, phosphorus and fluorine in some lunar lavas

Lunar sample 14310 is a feldspar-rich basalt which shows no evidence of shock deformation or recrystallization. Pyroxenes include Mg-rich orthopyroxene, pigeonite and augite; pyroxferroite occurs in the interstitial residuum. Plagioclase feldspars are zoned from An(96) to An(67), and variations in feldspar compositions do not necessarily indicate loss of Na during eruption of the lava. Opaque phases include ilmenite, ulvospinel, metallic iron, troilite, and schreibersite. Both whitlockite and apatite are present, and the interstitial residua contain baddeleyite, tranquillityite and barium-rich sanidine. Theoretical calculations provide estimates of partial pressures of oxygen, phosphorus, and fluorine in lunar magmas. In general, partial pressures of oxygen are restricted by the limiting assemblages of iron-wuestite and ilmenite-iron-rutile; phosphorus partial pressures are higher in lunar magmas than in terrestrial lavas. The occurrence of whitlockite indicates significantly lower fugacities of fluorine in lunar magmas than in terrestrial magmas.

Nash, W. P.↗
NASA NTRS1983

Petrology and chemistry of two 'large' granite clasts from the moon

Pristine granite clasts in Apollo-14 breccias 14321 and 14303 have estimated masses of 1.8 and 0.17 g, respectively. The 14321 clast is about 60 percent K-feldspar and 40 percent quartz, with traces of extremely Mg-poor mafic silicates and ilmenite. The 14303 clast is roughly 33 percent plagioclase, 32 percent K-feldspar, 23 percent quartz, 11 percent pyroxene, and 1 percent ilmenite; pyroxene and ilmenite are moderately Mg-rich; plagioclase and pyroxene are strongly zoned. Both clasts are severely brecciated, but monomict (pristine). Both have abundant graphic integrowths of K-feldspar with quartz. Unlike the majority of similar earth rocks, both clasts are devoid of hydrous phases. The bulk composition of the 14321 clast is similar to those of several other lunar granitic samples, but the 14303 clast is unique: it bears as close a resemblance to KREEP as it does to other lunar granites. Silicate liquid immiscibility may explain why the granites are low in REE relative to KREEP.

Warren, P. H.↗
NASA NTRS1986

Chemical and physical studies of type 3 chondrites. VII - Annealing studies of the Dhajala H3.8 chondrite and the thermal history of chondrules and chondrites

Samples of the Dhajala meteorite were annealed at 600-1000 C for 1, 2, 10, 20 and 100 h and their thermoluminescence (TL) properties were measured. After annealing at less than 900 deg, the TL sensitivity decreased by a factor of two; at higher temperatures, it fell by an order of magnitude. Data indicate that the annealing treatment caused the low-temperature feldspar in Dhajala to be converted to feldspar of a high-temperature (disordered) form. Low-temperature feldspar was found in the meteorite's TL-sensitive chondrules which comprised about 20 percent of those separated. It is suggested that these chondrules suffered greater crystallization of their mesostasis than the other chondrules, and equilibrated to lower temperatures. Based on TL data, there appears to be no relationship between post-metamorphic cooling rate and petrologic type for the 3.5-3.9 chondrites.

Keck, B. D.↗