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NASA NTRS1972

The lunar interior

The compressional velocities are estimated for materials in the lunar interior and compared with lunar seismic results. The lower crust has velocities appropriate for basalts or anorthosites. The high velocities associated with the uppermost mantle imply high densities and a change in composition to a lighter assemblage at depths of the order of 120 km. Calcium and aluminum are probably important components of the upper mantle and are deficient in the lower mantle. Much of the moon may have accreted from material similar in composition to eucrites. The important mineral of the upper mantle is garnet; possible accessory minerals are kyanite, spinel, and rutile. If the seismic results stand up, the high velocity layer in the moon is more likely to be a high pressure form of anorthosite than eclogite, pyroxenite, or dunite. The thickness of the layer is of the order of 50 km. Cosmic abundances can be maintained if the lower mantle is ferromagnesium silicate with minimal amounts of calcium and aluminum. Achondrites such as eucrites and howardites have more of the required characteristics of the lunar interior than carbonaceous chondrites. A density inversion in the moon is a strong possibility.

Anderson, D. L.↗
NASA NTRS1971

Hibonite, Ca2/Al, Ti/24O38, from the Leoville and Allende chondritic meteorites.

Hibonite was discovered in light-colored, Ca-Al-Ti-rich and Si-Fe-poor, achondritic inclusions of the Leoville and Allende HL-group chondrites. Two varieties of hibonite occur: one emits a bright red-orange luminescence under electron bombardment and has high amounts of Al2O3 (87.7; 87.9) and low amounts of MgO (0.65; 0.8) and TiO2 (0.68; 0.8). The other emits a bright blue luminescence and is low in Al2O3 (78.7; 79.2) and high in MgO (3.3; 3.7) and TiO2 (6.5; 7.9) (in wt. %). The oxide CaO is about the same in both varieties. It is suggested that the change in the color of the visible luminescence results from changes in composition. The origin of hibonite which occurs in complex mineral assemblages together with anorthite, gelhenite, wollastonite, aluminous diopside, andradite, Ca-pyroxene, perovskite, spinel, taenite, chromite, and pentlandite, and in close proximity to nodules containing calcite, whewellite, forsterite and many of the aforementioned phases, is discussed. The proposition that hibonite and associated phases originated by contact metamorphism and metasomatism of calcite-dolomite bearing assemblages cannot, at this time, be completely ruled out.

Keil, K.↗
NASA NTRS1972

Deformation, recrystallization, strength, and fracture of press-forged ceramic crystals.

Sapphire and ruby were very difficult to press-forge because they deformed without cracking only in a limited temperature range before they melted. Spinel crystals were somewhat easier and MgO, CaO, and TiC crystals much easier to forge. The degree of recrystallization that occurred during forging (which was related to the ease and type of slip intersections) varied from essentially zero in Al2O3 to complete (i.e., random polycrystalline bodies were produced) in CaO. Forging of bi- and polycrystalline bodies produced incoherent bodies as a result of grain-boundary sliding. Strengths of the forged crystals were comparable to those of dense polycrystalline bodies of similar grain size. However, forged and recrystallized CaO crystals were ductile at lower temperatures than dense hot-pressed CaO. This behavior is attributed to reduced grain-boundary impurities and porosity. Fracture origins could be located, indicating that fracture in the CaO occurs internally as a result of surface work hardening caused by machining.-

Rice, R. W.↗
NASA NTRS1972

The mineralogy of meteorites.

Of particular interest among minerals recently discovered in meteorites are five phosphate minerals, three of them unknown in terrestrial rocks; a chromium nitride and a silicon oxynitride; lonsdaleite and chaoite, new polymorphs of carbon; ringwoodite and majorite, the spinel and garnet analogs of olivine and pyroxene, respectively; a number of calcium- and aluminum-rich silicates in the Allende meteorite, a type III carbonaceous chondrite which fell in 1969; and several alkali-rich silicates found as inclusions in iron meteorites. Knowledge of the compositional range of the common minerals olivine, pyroxene, and plagioclase has also been greatly increased by recent researches.

Mason, B.↗
NASA NTRS1972

Equilibrium studies with a bearing on lunar rocks.

Review of the results of equilibrium studies of lunar rocks and of synthesized oxide and silicate phases performed in the temperature range from 1000 to 1400 C under strongly reducing conditions of a total pressure of 1 atm. Determined liquidus and solidus temperatures and sequence of appearance of crystalline phases are presented. The studies of synthesized mixtures are concentrated in two main areas, one dealing with subsolidus relations in titanate and spinel phases, the other with liquidus phase relations in simplified iron silicate systems.

Muan, A.↗
NASA NTRS1972

Electron microscopy of some experimentally shocked counterparts of lunar minerals.

Particulate samples of experimentally shocked olivine, enstatite, and apatite and their unshocked equivalents were thinned by ion bombardment and examined by transmission methods in a conventional (100 kV) electron microscope. Enstatite shock-loaded at a peak pressure of 250 kb was partly transformed to relatively dense inverse defect spinel. Magnesian olivine shocked at a peak pressure of 200 kb shows intense lattice deformation. Magnesian olivine shock-loaded at a peak pressure of 400 kb was recrystallized to very fine polycrystalline aggregates. Apatite shock-loaded at a peak pressure of 250 kb shows planar deformation elements and shock-induced imperfections.

Sclar, C. B.↗
NASA NTRS1973

Petrology of fine-grained rock fragments and petrologic implications of single crystal from the Luna 20 soil.

Only fine-grained rocks are present in the Luna 20 samples, and coarser-grained rocks are represented by fragments of single crystals. A petrologic study has been made of 47 fine-grained crystalline rocks, microbreccias, and glassy aggregates. In addition, a total of 33 single crystals of pyroxene, plagioclase, olivine, and spinel, in the size range from 125 to 500 microns, have been examined using electron microprobe and single-crystal X-ray diffraction techniques. The most abundant fine-grained crystalline rocks in the samples examined are recrystallized anorthositic norite and anorthositic troctolite. Gabbroic rocks, anorthosite, and KREEP basalt are present but not common. Most of the single crystals of pyroxene and plagioclase could have been derived from coarser-grained noritic, troctolitic, and anorthositic rocks. However, three of the 14 pyroxene crystals, and two of the five olivine crystals have Fe/(Fe + Mg) contents greater than 0.45 and are believed to have been derived from mare basalts or related rocks.

Cameron, K. L.↗
NASA NTRS1973

Luna 20 soil - Abundance and composition of phases in the 45-125 micron fraction.

Glass compositions in the Luna 20 soil indicate a minor contribution of mare rocks and a major contribution of highly feldspathic highland material. Glasses with the composition of highland basalt (anorthositic gabbro or norite) predominate in a range of highly aluminous glasses. The analyses of minerals in the soil show that the highland rocks have a unique assemblage of minerals that can readily be distinguished from the mineral assemblages of either mare or KREEP basalts. The soils are characterized by abundant anorthitic, low-Fe plagioclase. Highly magnesian orthopyroxenes, pigeonites, and augites are the most prominent pyroxenes. Unlike mare basalt pyroxenes, clinopyroxenes with intermediate Ca values are not abundant, but extreme iron enrichment toward pyroxferroite does occur. Olivines are more abundant than at other sites and are Mg-rich, low in Ca and Cr. Spinels with compositions approaching MgAl2O4 predominate over pleonastes and chromites. Ilmenite and metal are present but not abundant. The mineral compositions are consistent with derivation from a suite of highly feldspathic rocks in which highland basalt compositions predominate.

Reid, A. M.↗
NASA NTRS1973

Petrology of some lithic fragments from Luna 20.

Microscopic and electron microprobe studies were made of polished thin sections of part of a 30-mg sample of 250- to 500-micron lunar soil returned by Luna 20 from a point between Mare Fecunditatis and Mare Crisium. Very fine-grained lithic (crystalline) rock fragments, composing about one-fifth of the total sample, have mineralogical compositions equivalent to various types of gabbro, anorthositic gabbro, gabbroic anorthosite, and troctolite, with minor basalt. The textures now observed in these fragments are in large part metamorphic. Twenty-seven electron microprobe analyses of minerals from these fragments are presented, including olivine, plagioclase, pyroxene, spinel, nickel-iron, and a Zr-Ti-REE mineral possibly similar to 'phase B' of Lovering and Wark (1971). Analyses of seven melt inclusions and 28 defocused beam analyses of lithic fragments are also given. Some of the fragments contain 'gas' inclusions which, along with the fine grain size, are believed to indicate final crystallization under low pressure near surface conditions.

Roedder, E.↗
NASA NTRS1972

The lunar interior

The compressional velocities are estimated for materials thought to be important in the lunar interior and compared with lunar seismic results. The lower lunar crust has velocities appropriate for basalts or anorthosites. Anorthosite is preferred if lunar basalts result from a small degree of partial melting. The high velocities associated with the uppermost mantle imply high densities and a change to a lighter assemblage at depths of the order of 120 km. Ca- and Al-rich minerals are important components of both the lower crust and the upper mantle. Most of the moon may have accreted from refractory material rich in Ca, Al, U, and the rare-earth elements. The important mineral of the upper mantle is garnet; possible accessory minerals are kyanite, spinel and rutile. If the seismic results stand up, the high-velocity layer in the moon is more likely to be a high-pressure form of anorthosite than eclogite, pyroxenite, or dunite.

Anderson, D. L.↗
NASA NTRS1972

Apollo 15 rake sample microbreccias and non-mare rocks: Bulk rock, mineral and glass electron microprobe analyses

Quantitative electron microprobe data of Apollo 15 nonmare rake samples are presented. Bulk analyses of lithic fragments in the nomare rocks (expressed in oxide weight-percent) and the corresponding CIPW molecular norms are given. The mineralogy of the rocks and lithic fragments are also given; structural formulae for complete analyses and molecular end-members for all mineral analyses are included. The mineral analyses include pyroxene, olivine, plagioclase, barian K-feldspar, spinel and ilmenite, cobaltian metallic nickel-iron as well as SiO2-K2O-rich residual glass. Electron micropobe analyses (oxide weight percent) of glasses in loose fines and microbreccia samples and their CIPW molecular norms are presented along with electron microprobe data on bulk, mineral, and matrix glass from chondrules.

Hlava, P. F.↗
NASA NTRS1974

Effects of composition and testing conditions on oxidation behavior of four cast commercial nickel-base superalloys

Four cast nickel-base superalloys were oxidized at 1000 and 1100 C for times up to 100 hr in static air and a Mach 1 gas stream. The oxidation resistance was judged by weight change, metal thickness loss, depletion-zone formation, and oxide formation and morphology. The alloys which formed mostly nickel aluminate (NiAl2O4) and aluminum oxide (Al2O3) (B-1900, VIA, and to a lesser extent 713C) were more oxidation resistant. Poorer oxidation resistance was associated with the appearance of chromium sesquioxide (Cr2O3) and chromite spinel (738X). Refractory metal content had little effect on oxidation resistance. Refractory metals appeared in the scale as tapiolite (NiM2O6, where M represents the refractory metal). Thermal cycling in static air appeared to supply sufficient data for the evaluation of oxidation resistance, especially for alloys which form oxides of low volatility. For alloys of higher chromium levels with high propensities toward forming a chromium-bearing scale of higher volatility, testing under conditions of high gas velocity is necessary to assess fully the behavior of the alloy.

Lowell, C. E.↗
NASA NTRS1973

Shock remagnetization associated with meteorite impact at planetary surfaces

The stages of a cratering event are considered together with four distinct magnetization volumes, taking into account the jetted material, the ejecta, the impact melt, and shock-compressed material which remains in situ. Shock classifications are discussed along with mineralogical aspects of shock remagnetization, the behavior of iron sulfides, defect cubic spinels, ilmenite-hematite series, the Fe-Ti-O system, alloys phases, and silicates. Remagnetization mechanisms considered include a first order reversible crystallographic transition in bcc iron-nickel, a second order Curie point transition in fcc iron-nickel, shock-induced anisotropy, and shock melting of iron containing silicates. Experimental results are reported together with a hypothetical crater model.

Wasilewski, P. J.↗
NASA NTRS1973

Uranium concentration and distribution in six peridotite inclusions of probable mantle origin

Fission-track activation was used to investigate uranium concentration and distribution in peridotite inclusions in alkali basalt from six localities. Whole-rock uranium concentrations range from 24 to 82 ng/g. Most of the uranium is uniformly distributed in the major silicate phases - olivine, orthopyroxene, and clinopyroxene. Chromian spinels may be classified into two groups on the basis of their uranium content - those which have less than 10 ng/g and those which have 100 to 150 ng/g U. In one sample accessory hydrous phases, phlogopite and hornblende, contain 130 and 300 ng/g U, respectively. The contact between the inclusion and the host basalt is usually quite sharp. Glassy or microcrystalline veinlets found in some samples contain more than 1 microgram/g. Very little uranium is associated with microcrystals of apatite. These results agree with some earlier investigators, who have concluded that suboceanic peridotites contain too little uranium to account for normal oceanic heat flow by conduction alone.

Haines, E. L.↗
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

Selected Apollo 17 soils - Mineralogy and geochemistry of opaque and non-opaque phases

Soil samples 74220 ('orange soil'), 74241 and 75081 were sized, and the compositions of the opaque and silicate phases were determined. The ilmenites, particularly in 74241, contain up to 7.8 wt % MgO and display higher bireflectance than low-Mg ilmenites. They commonly contain exsolution-like chromite and rutile and occasionally are in association with native Fe in an assemblage probably resulting from reduction. The chromian ulvospinels are similar to Apollo 11 spinels in that they contain near-equal amounts of chromite and ulvospinel molecules. No primary chromites were observed. Most native Fe has No and Co contents of less than 1 wt %; some in 74220 contained 5-6% Ni and less than 1% Co in association with schreibersite.

Taylor, L. A.↗
NASA NTRS1974

Melting relations of the Allende meteorite

The proportions of major oxides in the Allende carbonaceous chondrite after partial reduction are remarkably similar to those in possible mantle material of the earth. When heated, the Allende meteorite generates a sulfide melt, a ferrobasaltic melt, and olivine with or without pyroxene, over a wide pressure range (5 to 25 kilobar). The silicate melt contains more sodium and less titanium than lunar ferrobasalts. An aggregate of the Allende chondrite rich in calcium and aluminum produces silica-undersaturated, calcium-rich melt and spinel over a wide pressure and temperature range. It is suggested that the earth's core contains significant amounts of both nickel and sulfur and that a 3:2 mixture of Allende bulk sample and calcium- and aluminum-rich agregates is closer in major element abundances than either of these components to the average composition of the moon.

Seitz, M. G.↗
NASA NTRS1973

Apollo 16 rocks - Classification and petrogenetic model

The Apollo 16 rocks include cataclastic anorthosites, two varieties of unequilibrated breccia, two varieties of partly to fully equilibrated breccia, and a sequence of partially melted breccias. The latter, which dominate the Apollo 16 collection, include glass, divitrified glass, mesostasis-olivine-plagioclase rock, mesostasis-rich basalt, basalt, and poikilitic rocks. All sequence members contain vesicles and relics of plagioclase, olivine, pink spinel, and lithic fragments. Their equilibrated matrices define a series from glass, to a plagioclase-olivine-mesostasis assemblage displaying spherulitic and skeletal shaped crystals, through a plagioclase-pyroxene-olivine assemblage displaying euhedral shaped crystals. Such data suggest that the sequence lithologies were derived from breccias or soils that were partially melted in an impact event.

Warner, J. L.↗