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Grove, T. L.

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

28 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Effects of kinetics on the crystallization of quartz normative basalt 15597 - An experimental study

Equilibrium experiments on a residual liquid composition from the dynamic crystallization study on quartz normative basalt (QNB) 15597 are used to evaluate the effects of kinetics on the crystallization of pyroxene-porphyritic basalts. The results indicate that the liquids coexisting with pyroxene phenocryst rims before the precipitation of groundmass plagioclase + pyroxene have left the equilibrium liquid line of descent and metastably penetrated the plagioclase primary phase volume. The precipitation of groundmass plagioclase + pyroxene brings the basalt system closer to equilibrium with respect to the residual liquid and crystals. At rapid cooling rates pyroxene phenocryst growth produces substantial compositional gradients in the residual silicate liquid at the pyroxene/liquid interface. The compositional gradients enhance the nucleation and growth of groundmass phases at the phenocryst interface, because effects related to constitutional supercooling for these phases (e.g., plagioclase, pyroxene, etc.) favor nucleation at the interface.

Grove, T. L.↗
NASA NTRS1977

Laser Ar-39-Ar-40 study of Apollo 17 basalts

Three Apollo 17 basalts were studied by the laser Ar-39-Ar-40 method. The 70215 basalt has a normal well-behaved Ar-39-Ar-40 release pattern; the 70017 basalt has a disturbed release pattern which indicates a limited intermediate maximum age followed by a broad low-age region; and the 75035 basalt has a pattern initially similar to 70017 that is followed by a high-temperature maximum age. The laser study shows that all mineral systems in 70215 have small and uniform temperature losses, while the laser-determined ages for 70017 and 75035 are, apparently, primarily controlled by the minerals containing mesostasis inclusions. It is possible that the drop in ages observed by the conventional Ar-39-Ar-40 method was due not only to recoil of Ar-39 during neutron irradiation but also to gas loss from some minerals. It is suggested that the plagioclases are the best minerals to use for a reliable age.

Schaeffer, O. A.↗
NASA NTRS1977

Cooling histories of Apollo 15 quartz-normative basalts

Controlled cooling rate studies of vitrophyre 15597 are used to calculate the physical properties of a quartz-normative magma as well as cooling histories of Apollo 15 quartz-normative basalts (QNB). Pyroxene phenocrysts of a QNB magma do not settle appreciably during the cooling of the flow unit; this behavior is consistent with the small degree of chemical differentiation that occurred between members of the suite. Two types of cooling histories for QNB are discerned. The vitrophyres experienced initial slow cooling followed by rapid cooling, and the coarse-grained microgabbros underwent slow nearly linear cooling histories. Textural evidence suggests that lunar vitrophyres crystallized near the top of the flow. It is suggested that the pattern of cooling may have been caused by the chilling of liquids that inherited early crystals in the interior of the flow.

Grove, T. L.↗
NASA NTRS1977

Slowly cooled microgabbros 15555 and 15065

An experimental study involving equilibration of Apollo 15 samples 15555 and 15065 in high-purity iron capsules is described. Comparison of mineral zoning trends with the experimental sequence suggests that the early crystallizing phases in the rock maintained surface equilibrium with the liquid. Olivine and pyroxene chemistry indicates that 15555 cooled slightly more rapidly than 15065, which cooled at approximately 0.2-0.3 C/day. It is suggested that 15065 and 15555 represent liquid compositions, and that these liquids appear to have been fractionated during ascent through the crust (15065), or to have been derived from an olivine-pyroxene source (15555) with Fe/(Fe + Mg) approximately equal to 0.73 at a depth between 150-200 km.

Walker, D.↗
NASA NTRS1977

Experimental study of pyroxene-liquid interaction in quartz-normative basalt 15597

Equilibrium and controlled cooling rate experiments on a synthetic analog of Apollo 15 quartz normative basalt 15597 are reported. While the partitioning of the major elements Ca, Mg, and Fe between pyroxene and liquid is rate independent, the K sub D parameter for Fe/Mg, which is calculated for low-Ca pyroxene, is temperature dependent. It is suggested that chemical trends observed in lunar pyroxenes are a consequence of three rate processes. The processes are (1) rate-dependent suppression of crystallization of other phases until lower temperature alters liquid composition and, therefore, the composition of the pyroxene that crystallizes; (2) the efficiency of fractional crystallization and the extent of crystal zoning are rate dependent; and (3) the partitioning of Al2O3, TiO2, and Cr2O3 between pyroxene and liquid depends on cooling rate.

Grove, T. L.↗
NASA NTRS1975

Origin of titaniferous lunar basalts

Delineation of low pressure phase equilibria in the composition space relevant to titaniferous lunar basalts demonstrates a significant degree of control by those equilibria on the compositions of the basalts. The existence of two distinct chemical groups of basalts (high and low K) which cannot be related one to the other by fractional crystallization at any pressure, suggests that melting is responsible for the two groups. Consideration of the pressure shift required to produce the differences between groups constrains magma segregation to have occurred in the outer 150 km of the moon. It is difficult to relate low-Ti and high-Ti basalts to the same source region. The preferred source region of high-Ti basalts, based on phase equilibrium considerations, is a late ilmenite-rich cumulate produced from the residual liquid of the primordial differentiation of the outer portions of the moon. This ilmenite-rich layer is sandwiched between the lunar feldspathic crust and a complementary mafic cumulate.

Walker, D.↗
NASA NTRS1974

The petrology of the Apollo 17 mare basalts

Petrographic studies of Apollo 17 mare basalts indicate that 70215 and 71569 arrived at the lunar surface as liquids. Low-pressure melting experiments show that compositional variations within the Apollo 17 and Apollo 11 ophitic basalt suites may be generated by near-surface fractional crystallization of liquids with compositions similar to 70215 and 70017. High-pressure melting experiments show that liquids similar in composition to 70017 and 70215 can be generated by partial melting of an olivine+clinopyroxene+Fe-Ti-oxide source at depths of 100-150 km within the moon.

Longhi, J.↗
NASA NTRS1973

Origin of lunar feldspathic rocks

Melting experiments and petrographic studies of lunar feldspathic rocks reveal possible genetic relationships among several compositionally and mineralogically distinct groups of lunar rocks and soil fragments. Dry, low PO2 partial melting of crustal anorthositic norites of the anorthositic-noritic-troctolitic (ANT) suite produces liquids of the KREEP-Fra Mauro basalt type; dry, low PO2 partial melting of pink spinel troctolite (PST) produces liquids of the 'very high alumina basalt' or microtroctolite type. Both ANT and PST are probable components of the primitive terra crust. If crystal fractionation in a cooling basaltic liquid could have produced such a crust, it would also produce a mafic interior capable of yielding mare basalts by later remelting at depth.

Walker, D.↗
NASA NTRS1973

Experimental petrology and origin of rocks from the Descartes Highlands

Petrographic studies of Apollo 16 samples indicate that rocks 62295 and 68415 are crystallization products of highly aluminous melts. 60025 is a shocked, crushed and partially annealed plagioclase cumulate. 60315 is a recrystallized noritic breccia of disputed origin. 60335 is a feldspathic basalt filled with xenoliths and xenocrysts of anorthosite, breccia, and anorthite. The Fe/(Fe+Mg) of plagioclase appears to be a relative crystallization index. Low pressure melting experiments with controlled Po2 indicate that the igneous samples crystallized at oxygen fugacities well below the Fe/FeO buffer. Crystallization experiments at various pressures suggest that the 62295 and 68415 compositions were produced by partial or complete melting of lunar crustal materials, and not by partial melting of the deep lunar interior.

Walker, D.↗