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Mineralogy, chemistry and origin of KREEP /potassium, rare earth element and phosphorus/ component in Apollo 12 soil and breccia samples from Ocean of Storms
Lunar rocks 12063,9 and 12004,11 opaque mineralogy and textural feature, comparing to apollo 11 samples
Petrological, mineralogical, and chemical investigations of the B-1 Luna 16 sample have revealed that the sample is a fine-grained ophitic basalt which is distinguished from the Apollo samples by containing a single pyroxene, an ilmenite content intermediate to that of the Apollo samples, and subequal amounts of pyroxene and plagioclase. It is also distinguished by a high Sr content and a high K/U value.
A geological and mineralogical study of the Potrillo volcanics is reported. The investigation consisted first of field mapping to establish and identify the different rock types and volcanic features in order to determine the geological history. Next, samples were collected and analyzed petrographically to determine suitable rocks from the various stratigraphic units for study of plagioclase. Samples selected for further study were crushed and the plagioclase extracted for the determination of composition and structural state. These results were then related to the petrology and crystallization of the basalt.
Mineralogical properties of calcic plagioclase have been analyzed using U-stage, microprobe, X-ray precession cameras, and a 650-kV electron microscope. The orientation of the optical indicatrix in lunar and eucrite anorthites is described with Euler angles. All crystals, except one, show strong b- and diffuse c-reflections in precession photographs. In 10017, b-split-reflections have been found. Dark-field electron micrographs of 14310 anorthite show both large and small b-antiphase domains, and an exsolution structure in crystals that display b-split reflections in the diffractogram. Diffuseness of c-reflections in X-ray photographs and the inability to resolve c-domains in electron micrographs in An 94 anorthite of 14310 indicate relatively rapid cooling of this rock compared to plutonic rocks.
The lithologic types found in the soil at the Luna site are characterized, and their mineralogical and petrological significance is discussed. Chemically, the Luna 20 and Apollo 16 soil samples are similar, but the Luna 20 soil is slightly depleted in aluminum and calcium and enriched in iron and magnesium relative to the Apollo 16 soils. This slight difference may be a result of the presence of a minor amount of mare material in the Luna 20 soil and its apparent absence in the Apollo 16 soils.
Data published in the literature and original results of mineralogical and petrological analyses of Apollo 16 rocks and fines indicate that Apollo 16 and Luna 20 sites are dominated by plagioclase-rich rocks with minor olivine and/or pyroxene. Data suggest that shock, brecciation, and recrystallization have largely eliminated primary textures. In general, all data are consistent with derivation from ejecta blankets produced from plagioclase-rich rocks by impacts. The lunar crust is discussed as a product of an early differentiation of the entire moon, and Mg/Fe data for experimental olivine-liquid and olivine-orthopyroxene equilibria are used as constraints to examine compositional data for rocks, glasses, and fragments in the light of specific models for crystal-liquid differentiation.
Unsorted powder and grains larger than 0.5 mm from the L-16-19-118 lunar sample consisted of eight basaltic fragments, four fragments of breccias (of which one was quite light), one white grain (maskelynite), one chondrule, and slagged dark partially glassy chunks. The mineralogical composition of all rounded particles led to the assumption that they are all of lunar origin; but their presence in the regolith indicates formation of chondrulic meteorites. The existence of several grains of pyroxene coated with a thin glassy film merits attention.
Petrographic and mineralogical features of fragments of magmatic rock of regolith from the Sea of Fertility are examined. The textures and mineral composition vary in relation to the type of rock. More than 50 X-ray spectral analyses of minerals (olivine, pyroxenes, plagioclases, and ores) were made; their chemical composition varies even within the limits of individual rock fragments.
Based on a synthesis of chemical data for over 200 samples, the nonmare rocks with fine grained melt textures can be classified into 7 major groups: anorthositic basalts, troctolitic basalts, VHA basalts, Apollo 14-type KREEP basalts, Apollo 15-type KREEP basalts, Apollo 17-type KREEP basalts, and aluminous mare basalts. Review of chemical, mineralogical, textural and experimental evidence leads to preferred hypotheses for the origins of these rocks; those hypotheses are discussed in detail.
Mineralogical, petrological, and chemical analyses, along with Rb-Sr age and Ar-40/Ar-39 measurements, were carried out with the B-1 sample returned from the Luna 16 mission. The sample, weighing 62 mg, is a fine-grain basalt of ophitic structure. It differs from the Apollo samples in that the pyroxene and plagioclass contents are almost identical, and the ilmenite content (7%) lies between those of the Apollo-11 and Apollo-12 samples. Chemically, it is characterized by a high Sr content and a high K/U ratio.
Rock 75035 is a medium-grained, holocrystalline, subophitic ilmenite basalt collected from the rim of Camelot Crater, and is believed to represent the subfloor basalts of the Taurus-Littrow valley. The rock consists of the major minerals pyroxene (45%), plagioclase (31%), and ilmenite (17%). Minor minerals include cristobalite (about 5%), troilite, native Fe, tranquillityite, baddeleyite, zirconolite, and rare ulvospinel. No olivine or armalcolite was observed in the specimen 75035,76. Mineralogically and chemically, as well as in age, this rock is similar to others collected from Camelot and other stations during the Apollo 17 mission. These rocks are almost identical to the Type B ilmenite basalts of Mare Tranquillitatis.
Chemical results from four samples of Martian fines delivered to Viking landers 1 and 2 are remarkably similar in that they all have high iron; moderate magnesium, calcium, and sulfur; low aluminum; and apparently very low alkalies and trace elements. This composition is best interpreted as representing the weathering products of mafic igneous rocks. A mineralogic model, derived from computer mixing studies and laboratory analog preparations, suggests that Mars fines could be an intimate mixture of about 80% iron-rich clay, about 10% magnesium sulfate (kieserite), about 5% carbonate (calcite), and about 5% iron oxides (hematite, magnetite, maghemite, goethite). The mafic nature of the present fines (distributed globally) and their probable source rocks seems to preclude large-scale planetary differentiation of a terrestrial nature.
Breccia 14063,14 is a complex, probably pre-Imbrian, unmetamorphosed breccia dominated almost entirely by mineral clasts. Electron-probe and microscope examination showed at least four distinct lithologies in a centimeter-sized thin-section. Examination of each lithology showed or suggested the following contributing rock types or mineralogies: (1) dunite with minor chromite, very high-Mg ilmenite and bronzite; (2) spinel troctolite with olivine and Mg-Al spinel; (3) high-Ti mare-like basalt with high-Mg ilmenite and coarse pyroxene; (4) low-KREEP noritic breccia; (5) anorthosite; (6) very Ni-rich Fe metal.
The interpretation of asteroid reflectance spectrophotometry in terms of mineralogical types gives inferred mineral assemblages for about 60 asteroids. Asteroid surface materials are compared with similar materials that make up many meteorites. The absence of asteroids with spectra that match identically the ordinary chondrites is noted.
The use of general and specific diagnostic spectral features and parameters to interpret most of the published high-quality reflectance spectra of asteroids is discussed. Such diagnostics are shown to provide the most complete and sophisticated mineralogically and petrologically based interpretation of the asteroid surface materials. Previous investigations of asteroid surface materials are exhaustively reviewed, emphasizing the general approaches employed, sources of information, previous characterizations of asteroid surface materials, and asteroid spectral groups. The interpretive methodology is then applied to spectral reflectance data for many individual members of the various spectral groups. A range of mineral assemblages similar to certain meteorite classes is identified, and evidence is presented for a selective high-temperature event that melted certain asteroid parent bodies and permitted their differentiation as some function of distance from the sun or the protosun and of the size of the protoasteroid. Possible candidates are proposed for the source bodies of different meteorite groups.
Results are summarized for a consortium study of the chemistry, mineralogy, and petrology of seven Luna 24 fragments greater than 1 mm in size and having a mass of about 2 mg each. The fragments include four samples of mare ferrobasalt composition, one vitrophyre with the composition of a Mg-rich VLT mare basalt, one agglutinate, and one plagioclase fragment. It is found that: (1) the ferrobasalt is a highly fractionated mare rock very low in alkalis and TiO2, is similar to the less fractionate Apollo 17 VLT basalts, and is quite low in large-ion lithophile trace-element content; (2) the rare-earth-element patterns of the ferrobasalts are typical of VLT basalt, but some ophitic basalts have positive Eu anomalies, while others have negative Eu anomalies typical of mare basalts; and (3) the agglutinate is feldspathic and similar in composition to soil fines in Fe, Cr, Ca, and Al.
Results of a detailed mineralogical and textural study of the HAL (Hibonite ALlende) inclusion of the Allende meteorite, which has been found to exhibit no Mg-26 excesses despite very high Al-27/Mg-24 ratios and large fractionation effects with small nuclear effects in its Ca, are reported. The inclusion is found to consist of three up to 1-mm diameter hibonite crystals partially surrounded by a black rim resembling a devitrified glass and containing an anisotropic Al-Fe oxide, which is in turn surrounded by a 2-mm thick friable rim sequence consisting of five layers distinguishable by mineral composition. From the available evidence, it is concluded that each of the layers of the friable rim formed by the accretion of an assemblage of condensate grains rather than by the complete reaction of a HAL precursor with a nebular gas, thus explaining its unusual isotopic characteristics and supporting the conclusion that the solar nebular contained isotopically-distinct reservoirs.