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Grove, T. L.

Publications and source records attributed to Grove, T. L..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

The Early Differentiation History of Mars from W-182-Nd-142 Isotope Systematics in the SNC Meteorites

We report here the results of an investigation of W and Nd isotopes in the SNC (Shergottite-Nakhlite-Chassignite (martian)) meteorites. We have determined that epsilon W-182 values in the nakhlites are uniform within analytical uncertainties and have an average value of approx. 3. Also, while epsilon W-182 values in the shergottites have a limited range (from 0.3-0.7), their epsilon Nd-142 values vary considerably (from -0.2-0.9). There appears to be no correlation between epsilon W-182 and epsilon Nd-142 in the nakhlites and shergottites. These results shed new light on early differentiation processes on Mars, particularly on the timing and nature of fractionation in silicate reservoirs. Assuming a two-stage model, the metallic core is estimated to have formed at approx. 12 Myr after the beginning of the solar system. Major silicate differentiation established the nakhlite source reservoir before approx. 4542 Ma and the shergottite source reservoirs at 4525 [sup +19 sub -21] Ma. These ages imply that, within the uncertainties afforded by the Hf-182-W-182 and Sm-146-Nd-142 chronometers, the silicate differentiation events that established the source reservoirs of the nakhlites and shergottites may have occurred contemporaneously, possibly during crystallization of a global magma ocean. The distinct W-182-Nd-142 isotope systematics in the nakhlites and the shergottites imply the presence of at least three isotopically distinct silicate reservoirs on Mars, two of which are depleted in incompatible lithophile elements relative to chondrites, and the third is enriched. The two depleted silicate reservoirs most likely reside in the Martian mantle, while the enriched reservoir could be either in the crust or the mantle. Therefore, the W-182-Nd-142 isotope systematics indicate that the nakhlites and the shergottites originated from distinct source reservoirs and cannot be petrogenetically related. A further implication is that the source reservoirs of the nakhlites and shergottites on Mars have been isolated since their establishment before approx. 4.5 Ga. Therefore, there has been no giant impact or efficient global mantle convection to thoroughly homogenize the Martian mantle following the establishment of the SNC source reservoirs.

Foley, C. Nicole↗
NASA NTRS2005

Phase Equilibrium Investigations of Planetary Materials

This grant provided funds to carry out phase equilibrium studies on the processes of chemical differentiation of the moon and the meteorite parent bodies, during their early evolutionary history. Several experimental studies examined processes that led to the formation of lunar ultramafic glasses. Phase equilibrium studies were carried out on selected low-Ti and high-Ti lunar ultramafic glass compositions to provide constraints on the depth range, temperature and processes of melt generation and/or assimilation. A second set of experiments examined the role of sulfide melts in core formation processes in the earth and terrestrial planets. The major results of each paper are discussed, and copies of the papers are attached as Appendix I.

Grove, T. L.↗
NASA NTRS2003

Early Petrologic Processes on the Ureilite Parent Body

We present a petrographic and petrologic analysis of 21 olivine-pigeonite ureilites, along with new experimental results on melt compositions predicted to be in equilibrium with ureilite compositions. We conclude that these ureilites are the residues of a partial melting/smelting event. Textural evidence preserved in olivine and pigeonite record the extent of primary smelting. In pigeonite cores, we observe fine trains of iron metal inclusions that formed by the reduction of olivine to pigeonite and metal during primary smelting. Olivine cores lack metal inclusions but the outer grain boundaries are variably reduced by a late-stage reduction event. The modal proportion of pigeonite and percentage of olivine affected by late stage reduction are inversely related and provide an estimation of the degree of primary smelting during ureilite petrogenesis. In our sample suite, this correlation holds for 16 of the 21 samples examined. Olivine-pigeonite-liquid phase equilibrium constraints are used to obtain temperature estimates for the ureilite samples examined. Inferred smelting temperatures range from approximately 1150 C to just over 1300 C and span the range of estimates published for ureilites containing two or more pyroxenes. Temperature is also positively correlated with modal percent pigeonite. Smelting temperature is inversely correlated with smelting depth--the hottest olivine-pigeonite ureilites coming from the shallowest depth in the ureilite parent body. The highest temperature samples also have oxygen isotopic signatures that fall toward the refractory inclusion-rich end of the carbonaceous chondrite-anhydrous mineral (CCAM) slope 1 mixing line. These temperature-depth variations in the ureilite parent body could have been created by a heterogeneous distribution of heat producing elements, which would indicate that isotopic heterogeneities existed in the material from which the ureilite parent body was assembled.

Singletary, S. J.↗
NASA NTRS1997

Phase Equilibrium Investigations of Planetary Materials

This grant provided funds to carry out experimental studies designed to illuminate the conditions of melting and chemical differentiation that has occurred in planetary interiors. Studies focused on the conditions of mare basalt generation in the moon's interior and on processes that led to core formation in the Shergottite Parent Body (Mars). Studies also examined physical processes that could lead to the segregation of metal-rich sulfide melts in an olivine-rich solid matrix. The major results of each paper are discussed below and copies of the papers are attached as Appendix I.

Grove, T. L.↗
NASA NTRS1996

Experimental Constraints on the Origin of Lunar High-Ti Ultramafic Glasses

Phase equilibria and dissolution rate experiments are used to develop a petrogenetic model for the high-Ti lunar ultramafic glasses. Near-liquidus phase relations of the Apollo 14 black glass, the most Ti-rich lunar ultramafic glass, are determined to 2.2-GPa. The liquidus is saturated with Cr-spinel at 1-atm, olivine between approximately 0.5- and 1.5-GPa, and low-Ca pyroxene + Cr-spinel above 1.5-GPa. Ilmenite does not crystallize near the liquidus and implies that high-Ti ultramafic glasses are not produced by melting of an ilmenite-saturated source. We infer that high-Ti ultramafic magmas are derived from low-Ti ultramafic parent magmas by assimilation of ilmenite +/- clinopyroxene +/- urKREEP +/- pigeonite in the shallow lunar interior. Heat is provided by adiabatic ascent of the low-Ti ultramafic primary magmas from the deeper lunar interior and crystallization of olivine during assimilation. The assimilation reaction is modeled by mass balance and requires that ilmenite and high-Ca pyroxene are assimilated in a approximately 3:1 ratio, a much higher ratio than the proportion in which these minerals are thought to exist in the lunar interior. In an effort to understand the kinetic controls on this reaction, the dissolution of ilmenite is examined experimentally in both low- and high-Ti lunar magmas. We find that ilmenite dissolves incongruently to Cr-spinel and a high-Ti melt. The dissolution reaction proceeds by a diffusion-controlled mechanism. An assimilation model for the origin of high-Ti melts is developed that leaves the magma ocean cumulates in their initial stratigraphic positions and obviates source hybridization models that require lunar overturn.

Wagner, T. P.↗
NASA NTRS1993

Petrologic constraints on the surface processes on asteroid 4 Vesta and on excavation depths of diogenite fragments

The eucrite-howardite-diogenite meteorite groups are though to be related by magmatic processes. Asteroid 4 Vesta has been proposed as the parent body for these basaltic achondrite meteorites. The similarity of the planetesimal's surface composition to eucrite and diogenite meteorites and the large size of the asteroid (r = 250 km) make it an attractive source, but its position in the asteroid belt far from the known resonances from which meteorites originate make a relation between Vesta and eucrite-howardite-giogenite group problematic. It has been proposed that diogenites are low-Ca pyroxene-rich cumulates that crystallized from a magnesian parent (identified in howardite breccias), and this crystallization process led to evolved eucrite derivative magmas. This eucrite-diogenite genetic relationship places constraints on the physical conditions under which crystallization occurred. Elevated pressure melting experiments on magnesian eucrite parent compositions show that the minimum pressure at which pyroxene crystallization could lead to the observed compositions of main series eucrites is 500 bars, equivalent to a depth of 135 km in a 4 Vesta-sized eucrite parent body. Therefore, the observation of diogenite on the surface of 4 Vesta requires a post-crystallization process that excavates diogenite cumulate from depth. The discovery of diogenite asteroidal fragments is consistent with an impact event on 4 Vesta that penetrated the deep interior of this planetesimal.

Grove, T. L.↗
NASA NTRS1993

Origin of high-Ti lunar ultramafic glasses

A series of high pressure melting experiments were performed on a synthetic analog of the Apollo 14 Black Glass. At 15 kb and 1400 C, olivine is the liquidus phase. At 25 kb and 1450 C, orthopyroxene and Cr-spinel crystallize. A multiple saturation point with olivine + orthopyroxene + spinel on the liquidus occurs at 20 kb and 1440 C. It was proposed that the high-Ti ultramafic glass evolved from a low-Ti Green Glass generated deep in the lunar interior that assimilated shallow-level, late stage cumulates of magma ocean differentiation. Heat for assimilation is provided by superheat of the low-Ti magma and melts high-Ca pyroxene and ilmenite cumulates at a depth of 100 km. This model is a variant of that proposed by Hubbard and Minear and rejected by Ringwood and Kesson.

Wagner, T. P.↗
NASA NTRS1991

High-pressure experiments on magnesian eucrite compositions - Constraints on magmatic processes in the eucrite parent body

Melting experiments were conducted on synthetic analogs of two magnesian eucrite clasts from howardites, Kapoeta clast rho and Yamato 7308 pigeonite-eucrite clast 1, at 1 atm and 1-kbar pressure at oxygen fugacities in the range of iron-wuestite (IW) to iron-quartz-fayalite (IQF). The compositions of liquids and coexisting minerals (olivine-low-Ca pyroxene-plagioclase spinel) were used to constrain possible melting and crystallization processes in the parent bodies of eucrite basalts. In agreement with previous studies, the experimental results at 1 atm indicate that the olivine-low-Ca pyroxene-plagioclase-spinel-liquid and olivine-low Ca pyroxene-spinel-liquid boundaries are reaction boundaries involving olivine. At 1 kbar, however, the olivine primary-phase volume shrinks, and the reaction relationship involving olivine disappears for both boundaries. The maximum pressure attained in a Vesta-sized eucrite parent body (EPB) is about 1 kbar, and these results provide important constraints on models relating the howardite-eucrite-diogenite (HED) meteorite association through melting and differentiation processes.

Bartels, K. S.↗
NASA NTRS1987

Experimental studies of crystal-melt differentiation in planetary basalt compositions

An important process that controls the evolution of magmas on and within planetary bodies is crystal-melt differentiation. Experimental studies of silicate melt solidification were performed on several planetary and terrestrial melt compositions, and experiments on one of these compositions in the microgravity environment of the space station would provide an opportunity to understand the factors that control crystal growth and crystal-melt exchange processes at crystal-melt interfaces during solidification. Experimental requirements are presented.

Grove, T. L.↗
NASA NTRS1987

Kinetics of mineral condensation in the solar nebula

A natural extension of the type of gas-mineral-melt condensation experiments is to study the gas-mineral-melt reaction process by controlling the reaction times of appropriate gas compositions with silicate materials. In a condensing and vaporizing gas-solid system, important processes that could influence the composition of and speciation in the gas phase are the kinetics of vaporization of components from silicate crystals and melts. The high vacuum attainable in the space station would provide an environment for studying these processes at gas pressures much lower than those obtainable in experimental devices operated at terrestrial conditions in which the gas phase and mineral or melt would be allowed to come to exchange equilibrium. Further experiments would be performed at variable gas flow rates to simulate disequilibrium vapor fractionation. In this type of experiment it is desirable to analyze directly the species in the gas phase in equilibrium with the condensed silicate material. This analytical method would provide a direct determination of the species present in the gas phase. Currently, the notion of gas speciation is based on calculations from thermodynamic data. The proposed experiments require similar furnace designs and use similar experimental starting compositions, pressures, and temperatures as those described by Mysen.

Grove, T. L.↗
NASA NTRS1985

The geologic history of quartz-normative and olivine-normative basalts in the vicinity of Hadley Rille (Apollo 15)

The geologic history of the quartz normative (QNB) and olivine normative (ONB) basalt types at Hadley Rille are discussed. A model for the geology of the mare basalts was constructed from a combination of field observations, sample chemistry, sample petrology and personal bias from terrestrial experience. The model proposes that the QNBs are the only mare lava type that is present as outcrop in the area traversed by the astronauts during the Apollo 15 mission. The returned QNB samples formed during a single eruptive phase of the Hadley Rille lava tube system. The ONB lavas are an exotic component transported to the site by a cratering event, or the ONBs are samples excavated from older are bedrock that was partly covered by the QNB lavas.

Grove, T. L.↗
NASA NTRS1980

Classification, experimental petrology and possible volcanic histories of the Apollo 11 high-K basalts

The Apollo 11 high-K basalt samples are classified into three textural categories: vitrophyric, anti-insertal, and antiophitic. Low-pressure phase equilibrium experiments and cooling rate studies were performed on a synthetic analog of 10085, 832. The dynamic crystallization experiments were designed to study textural development with: (1) a variable cooling rate from a constant initial temperature above the liquidus, and (2) cooling at a constant rate from variable initial temperatures below the liquidus. These experiments show that a variety of cooling rates initiated from temperatures both below and above the liquidus can produce all the observed textures. The results are consistent with the interpretation that all of the high-K basalt samples were derived from a single lava flow or lava lake.

Grove, T. L.↗
NASA NTRS1979

Comparison of dynamic crystallization techniques on Apollo 15 quartz normative basalts

The paper compares dynamic crystallization techniques used on Apollo 15 quartz normative basalts which show differences related to their method. The variation of pyroxene core major element chemistry with cooling rate is confirmed, and it is shown that the Fe loss from liquid is shifted toward the En-Di joint; it is suggested that the nucleation temperature and breakdown of equilibrium partitioning as a function of cooling rate dictate the core composition. It is concluded that the different crystallization behavior that results from the Fe-capsule and Fe-loop container methods is related to the nucleation kinetics.

Lofgren, G. E.↗
NASA NTRS1979

Crystallization kinetics in a multiply saturated basalt magma - An experimental study of Luna 24 ferrobasalt

The paper deals with the effects of kinetics on mineral/melt partitioning and on fractional crystallization for a Luna-24 ferrobasalt. The composition is nearly multiply saturated under lunar surface conditions, making it possible to study the response of several mineral phases to kinetic factors during cooling. The differential suppression of the temperature of appearance of olivine, clinopyroxene, and plagioclase causes changes in the liquid line of descent. The course of liquid line of descent is mapped as a function of the cooling rate, and the partitioning of elements between pyroxene/liquid and olivine/liquid is examined.

Grove, T. L.↗
NASA NTRS1978

The Luna 24 highland component

Highland lithologies represent a very small but significant component of the Luna 24 drill core. They consist predominantly of melt rocks and glasses of probable impact origin, which are distinguished from their mare counterparts by their CaO/Al2O3 (weight) ratios no more than 0.8 and Fe/(Fe + Mg) (atomic) ratios of no more than 0.4. Compositions equivalent to highland basalt dominate the melt rock and glass fraction. Minor lithologies include possible plutonic lithic and monomineralic fragments. The high proportion of highland basalt relative to the other highland lithologic types, the absence of KREEP basalts, and the low KREEP content of the highland melt rocks and glasses in the Luna 24 soil are also characteristic of the Luna 20 site located in the highland terrain south of Mare Crisium.

Bence, A. E.↗
NASA NTRS1978

Experimental petrology of very low Ti /VLT/ basalts

Synthetic analogs of Luna 24 ferrobasalt and an Apollo 15 green glass were subjected to iron capsule experiments to test hypotheses concerning the generation of Luna 24 ferrobasalt. Results of the experiments indicated that the Luna 24 ferrobasalt may be generated by near-surface fractionation of a Luna 24 green glass parent. Evidence for the parent magma which differentiated at or near the Mare Crisium site to yield the Luna 24 ferrobasalt may be found in the Luna 24 green glass and lithic fragments of vitrophyres.

Grove, T. L.↗