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Preliminary Characterization of Spinel Troctolite Clast Identified in Apollo Next Generation Sample Analysis (ANGSA) Core 73002

The lunar magnesian (Mg-) suite is a diverse lithological group composed of Mg-rich mafic minerals. The Mg-suite consists primarily of troctolites, norites, gabbronorites, and spinel troctolites. These rocks exhibit contradictory geochemical traits, with mafic minerals bearing high Mg# (molar 100×Mg/[Mg+Fe]) indicating primitive parental magmas, but also plagioclase saturation and enrichments in incompatible trace elements (i.e., KREEP) indicate more evolved parental magmas. A variety of models have been invoked to explain the occurrence and petrogenesis of the Mg-suite. Here, we report on a new spinel troctolite clast found in Apollo Next Generation Sample Analysis (ANGSA) program core 73002. Sample 73002 was acquired at Station 3 during Apollo 17 as the upper part of a double-drive tube with sample 73001. During processing, the spinel troctolite clast (0.066 g) was found at the 4.0–4.5 cm depth interval.

A. C. Stadermann↗
NASA NTRS1973

Spinel troctolite and anorthosite in Apollo 16 samples.

Review of the examination results on two Apollo 16 rocks recovered from the lunar highlands which probably represent contrasting types of 'primitive' lunar cumulates. One is a microbreccia containing a large lithic fragment of spinel troctolite, while the other is a shock-brecciated anorthosite. The reviewed results suggest that, if the two rock groups formed from the same parent magma type, the spinel troctolite must have formed early in the differentiation sequence as the result of crystal settling in the melt, whereas the anorthosite must have formed as a later cumulate, possibly by flotation.

Prinz, M.↗
NASA NTRS1974

Reinvestigation of the olivine-spinel transformation in Ni2SiO4 and the incongruent melting of Ni2SiO4 olivine

The olivine-spinel transformation and the melting behavior of Ni2SiO4 were investigated over the PT ranges of 20-40 kbar, 650-1200 C, and 5-13 kbar, 1600-1700 C, respectively. It was confirmed that Ni2SiO4 olivine melts incongruently at high pressures and that it is a stable phase until melting occurs. The PT slope of the incongruent melting curve is approximately 105 bars/deg. The olivine-spinel transformation curve was shown to be a reversible univariant curve, and could be expressed by the linear equation P(bars) equals 23,300 + 11.8 x T(deg C). The transformation curve determined by Akimoto et al. (1965) is nearly parallel to that of the present work, but lies at pressures about 12% lower.

Ma, C.-B.↗
NASA NTRS1980

Experimental mineral/liquid partition coefficients of the rare earth elements /REE/, Sc and Sr for perovskite, spinel and melilite

Experimental determinations of the mineral/liquid partition coefficients of REE (La, Sm, Eu, Gd, Tb, Yb and Lu), Sc and Sr are reported for the minerals perovskite, spinel and melilite in synthetic systems. Perovskite concentrates light REE with respect to the residual liquid but shows no preference for heavy REE. Spinel greatly discriminates against the incorporation of REE, especially light REE, into its crystal structure. The partition of REE into melilite from a silicate liquid is quite dependent upon both the bulk melt and melilite solid-solution (gehlenite and akermanite components) compositions. As such, melilite can be enriched in REE or will reject REE with corresponding strong negative or strong positive Eu anomalies, respectively.

Nagasawa, H.↗
NASA NTRS1980

Spinel cataclasites in 15445 and 72435 - Petrology and criteria for equilibrium

The problem of establishing the existence of equilibrium among the coexisting phases in the rock is addressed by presenting petrographic and mineral chemistry data on a new spinel cataclasite from 15445 (clast H) and data more extensive than those previously available on two clasts in 72435. Criteria useful in reconstructing the original petrology of these and other spinel cataclasites are analyzed by considering equilibrium among the different phases, that is, the mono- or polymict nature of these cataclasized samples. Finally, the role of impact processes in disturbing the equilibria is discussed.

Baker, M. B.↗
NASA NTRS1982

Sorption of noble gases by solids, with reference to meteorites. II - Chromite and carbon. III - Sulfides, spinels, and other substances; on the origin of planetary gases

The trapping of noble gases by chromite and carbon, two putative carriers of primordial noble gases in meteorites, was studied by synthesizing 19 samples in a Ne-Ar-Kr-Xe atmosphere at 440-720 K. Noble gas contents are found to approximately obey Henry's Law, but only slight correlations are found with composition, surface area, or adsorption temperature. Geometric mean distribution coefficients for bulk samples and HCl residues in 10 cu cm STP/g atm are: Xe 100, Kr 15, Ar 3.5, and Ne 0.62. Elemental fractionation data support the suggestion of Lewis et al. (1977) that chromite and carbon in C2 and C3 chondrites were formed by the reaction: Fe, Cr + 4CO yields (Fe, Cr)3O4 + 4C + carbides. In contrast to meteoritic minerals, the synthetic specimens show no isotopic fractionation of noble gases. In a subsequent study, attention is given to the cases of sulfides and spinels, on the way to consideration of the origin of planetary gases. Sulfides showed three distinctive trends relative to chromite or magnetite. The elemental fractionation pattern of Ar, Kr and Xe in meteorites, terrestrial rocks and planets resembles the adsorption patterns on the carbons, spinels, sulfides, and other solids studied. The high release temperature of meteoritic noble gases may be explained by transformation of the physisorbed or chemisorbed gas. The ready loss of meteoritic heavy gases on surficial oxidation is consistent with adsorption, as is the high abundance.

Yang, J.↗
NASA NTRS1982

Experimental determination of the spinel-garnet boundary in a Martian mantle composition

The high pressure reaction orthopyroxene + clinopyroxene + spinel to garnet + olivine is applicable to the mantle of Mars. Experimental reversals of this reaction in the system CaO-MgO-FeO-Al2O3-SiO2 have been made in the range 1000-1200 C using the bulk composition proposed by Morgan and Anders (1980). At 1000 C, 1100 C, and 1200 C the garnet-out equilibrium is bracketed at 10.8 + or - 0.5, 12.6 + or - 0.5, and 15.2 + or - 0.5 kbars, respectively. A dP/dT slope of 14.0 bar/K at 1000 C increasing to 26.0 bar/K at 1200 C has been inferred. Depending on bulk composition, the mantle of Mars is inferred to have a phase assemblage of either olivine + clinopyroxene + orthopyroxene + garnet or olivine + clinopyroxene + garnet + spinel. In the second, the partial melts will not be buffered by olivine and orthopyroxene and will have markedly lower silica activities than those of the terrestrial mantle.

Patera, E. S.↗
NASA NTRS1983

Catalytic recombination of nitrogen and oxygen on iron-cobalt-chromia spinel

The energy-transfer catalytic recombination coefficient for nitrogen and oxygen recombination on iron-cobalt-chromia spinel is inferred from stagnation-point heat flux measurements in dissociated arc-jet flow. This material was coated on several Space Shuttle Orbiter thermal protection tiles. The resulting coefficients are correlated with an Arrhenius model for convenience, and these expressions may be used to account for catalytic recombination in predictions of the heat flux on the spinel-coated tiles flown on several Space Shuttle Orbiter flights. The results are compared with those inferred by Rakich, Stewart, and Lanfranco from an Orbiter flight and arc-jet experiments. Good agreement is obtained for oxygen recombination, but agreement for nitrogen is poor.

Scott, C. D.↗
NASA NTRS1985

Mineral chemistry and origin of spinel-rich inclusions in the Allende CV3 chondrite

The present electron probe microanalysis of 20 spinel-rich inclusions in Allende indicates that the mineralogy of spinel-rich Allende inclusions is similar to that of fine grained Ca, Al-rich inclusions (CAIs) in ALH-77003 and rims on coarse grained CAIs in Allende. The mineralogy, mineral chemistry, and bulk chemistry of the inclusions indicate that they are not primitive aggregates of crystalline nebular condensates, but rather aggregates of minute concentric objects that are presently interpreted to be a fractionated distillation residue that lost Ca, Si-rich partial melt. It is suggested that interstellar dust aggregates were melted or distilled into Allende inclusions by aerodynamic drag heating, in regions of the nebula where the dust/gas ratio was so enhanced that the local oxygen fugacity was raised by several order of magnitude and liquids became thermodynamically stable.

Kornacki, A. S.↗
NASA NTRS1993

Trace element compositions of spinel-rich refractory inclusions from the Murchison meteorite

Three spinel-rich, perovskite-bearing, pyroxene-rimmed, hibonite-free inclusions from the Murchison C2 chondrite have volatility controlled, modified group II REE patterns. Two have high Eu/Yb ratios, two have small positive Ce anomalies and one has high refractory siderophiles for a group II inclusion. Two additional spinel-rich inclusions have subchondritic Ce/La ratios and negative Eu and Yb anomalies, the Eu anomalies being larger than the Yb ones. One of these inclusions is enriched in La relative to all HREE and the other is enriched in HREE relative to all LREE except La, possibly suggesting the presence of an ultrarefractory component in the latter. One hibonite-rich inclusion has a group III REE pattern with a negative Ce anomaly. A calcium dialuminate-bearing inclusion known to have crystallized from a melt at 2100-1800K has a modified group II REE pattern, rather than a pattern which would be predicted from the evaporation expected from such a droplet, e.g., a group III or ultrarefractory pattern. Volatile element contents of these inclusions are among the lowest found in any refractory inclusions.

Yoneda, S.↗
NASA NTRS1996

Diogenites: Cumulates from Asteroid 4 Vesta: Insights from Orthopyroxene and Spinel Chemistry

Cumulate rocks are important planetary lithologies, but they can be difficult to interpret. Important clues to the nature of their parental melts may still be present in the interiors of cumulus phases. However, in some cases, even the cores of the cumulus grains may have been modified by postcrystallization reactions with trapped melt and other cumulus phases. We have previously studied the major-, minor-, and trace-element chemistry of orthopyroxene from a suite of diogenites and concluded that their chemical attributes can best be explained by crystallization from parental melts that were derived from a depleted mantle source that had already experienced eucrite removal. However, we and others have had difficulty explaining the great range in concentration of minor elements (Al, Ti) and trace elements (REE, Y, Zr) if all diogenites were derived from a single magmatic system. Therefore, we have investigated the chemistry of diogenitic spinels to see if they still held clues to the diogenite parental melt compositions. Although spinel is low in abundance in diogenites (<5 vol%) it still may hold clues to the maomatic and metamorphic history of these rocks.

Papike, James J.↗
NASA NTRS2000

Thermoelectric Properties of Selenides Spinels

Many compounds with the spinel structure type have been analyzed for their thermoelectric properties. Published data was used to augment experimental results presented here to select promising thermoelectric spinels.

thermoelectrics thermopower resistivity thermal co↗
NASA NTRS2014

Chromium Oxidation State in Planetary Basalts: Oxygen Fugacity Indicator and Critical Variable for Cr-Spinel Stability

Cr is a ubiquitous and relatively abundant minor element in basaltic, planetary magmas. At the reduced oxidation states (<FMQ) of many planetary basalts Cr is present in melts as both divalent and trivalent forms. The ratio of trivalent to divalent Cr present in the melt has many consequences for the stability and Cr concentration of magmatic phases such as spinel, clinopyroxene, and olivine. However, understanding the Cr valence in quenched melts has historically been plagued with analytical issues, and only recently has reliable methodology for quantifying Cr valence in quenched melts been developed. Despite this substantial difficulty, the pioneering works of Hanson and Jones and Berry and O'Neill provided important insights into the oxidation state of Cr in in silicate melts. Here we present a series of 1-bar gas mixing experiments performed with a Fe-rich basaltic melt in which have determined the Cr redox ratio of the melt at over a range of fO2 values by measuring this quantity in olivine with X-ray Absorption Near Edge Spectroscopy (XANES). The measured Cr redox ratio of the olivine phenocrysts can be readily converted to the ratio present in the conjugate melt via the ratio of crystal-liquid partition coefficients for Cr3+ and Cr2+. We have applied these results to modeling Cr spinel stability and Cr redox ratios in a primitive, iron-rich martian basalt.

Bell, A. S.↗
NASA NTRS2019

Fine-Grained, Spinel-Rich Ca-Al-Rich Inclusions From The Reduced CV3 Chondrite Efremovka: A Genetic Link To Wark-Lovering Rims?

Fine-grained, spinel-rich Ca-Al-rich inclusions (FGIs) in carbonaceous chondrites, mostly CV3 chondrites, are interpreted as aggregates of nebular gas-solid condensates that escaped significant melting [1]. Multiple lines of evidence suggest a condensation origin for FGIs, including their layered structures and irregular shapes and the fine grain size of numerous spinel-cored nodules [e.g., 2,3], and the distinctive volatility-fractionated group II rare earth element patterns of bulk inclusions and their mineral constituents [e.g., 4,5]. The origin and nature of FGIs are poorly constrained because of their fine grain sizes and intimate intergrowths of refractory phases, combined with their susceptibility to secondary parent body alteration processes, making detailed mineralogical and petrologic characterizations difficult using scanning electron microscope (SEM) and electron microprobe techniques. In this study, we present preliminary transmission electron microscope (TEM) analyses of pristine FGIs from the reduced CV3 chondrite Efremovka in order to provide the detailed characterization of their micrometer- to nanometer-scale textures and chemical compositions. Our goals are to better understand the formation processes and conditions of FGIs in the early solar nebula and to explore their possible genetic relationship with other early-formed refractory inclusions and their rims.

Keller, L. P.↗
NASA NTRS2020

Condensation, Partial Melting and Evaporation Processes Influence the Bulk Compositions of Spinel-Cored Spherules in the CO3.1 Chondrite Miller Range 90019

Here we focus on spinel-cored spherule calcium-aluminum rich inclusions (CAI), dominantly ~75-80 microns in diameter in the CO3.1 chondrite Miller Range 90019, which make up ~ 12 % of the fine-grained CAIs in one thin section. Their mineralogical content ranges from rare grossite- and hibonite-bearing varieties, through perovskite-melilitebearing, to fassaite-bearing and finally anorthitebearing. Non-spherical CAIs have been divided into 4 other groups, defined based on mineralogical abundances. We also characterized a group of AOAs from this sample. No glass has been recognized in any inclusions. Some relatively evolved members (anorthite-, spinel- + fassaite-bearing) among the spherules are found engulfed in AOAs. We characterized the bulk compositions of ~145 CAIs and AOAs in this meteorite, derived from EDS-x-ray mapping of the inclusions. We determined bulk compositions both with and without Wark-Lovering rims (when present), which are largely composed of diopside  forsterite. The balance of the inclusions appear to have not been melted or partially melted, but rather they have textures that indicate they are condensates, often modified by extensive reaction with nebular gases. This presents the opportunity to examine effects on the bulk compositions of spherules resulting potentially from melting plus evaporation. Other aspects of this suite of refractory inclusions have been discussed in these abstracts. Oxygen isotope variations in one spherule were presented in [4]. The latter study showed a complex history of reaction with nebular gases possessing a variety of Oisotope compositions. Additional O isotopic studies of inclusions in this work are included in Mane et al.

Ross, D. K.↗