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Prinz, M.

Publications and source records attributed to Prinz, M..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Metamorphic reactions in mesosiderites - Origin of abundant phosphate and silica

In light of a study of the Emery mesosiderite, it is determined that the high modal abundances of merrillite and tridymite in most mesosiderites are attributable to redox reactions between silicates and P-bearing Fe-Ni metal within a limited T-fO2 range at low pressure. The recalculated amounts of dissolved P and S in the metallic portion of Emery reduce the metal liquidus temperature to less than 1350 C, and the solidus to less than 800 C, so that the mixing of liquid metal with cold silicates would have resulted in silicate metamorphism rather than melting. This redox reaction and redistribution of components between metal and silicates illuminates the complexities of mesosiderite processing, with a view to the recalculation of their original components.

Harlow, G. E.↗
NASA NTRS1982

Metamorphism in mesosiderites

Previous studies of mesosiderites have identified a metamorphic overprint in these meteorites. However, the effects and implications of this overprint have not yet been explored in detail. The present study documents several important textural and chemical features of the mesosiderites. The components of mesosiderites are examined, taking into account orthopyroxenites, olivine in clasts, mesosiderite mafic clasts, and metal. The characteristics of the silicate matrix of the mesosiderites is explored, and textural and chemical evidence of metamorphism is discussed, giving attention to coronas on olivine clasts, overgrowths on Mg-pyroxene clasts, rims on iron rich pyroxene grains, poikiloblasts of plagioclase, and resorption of clasts. Aspects of redox formation of merrillite are considered along with the causes and the implications of metamorphism. It is found that metamorphism has radically changed the texture of the silicate fraction of the mesosiderites.

Delaney, J. S.↗
NASA NTRS1982

The Tucson iron and its relationship to enstatite meteorites

The Tucson meteorite was studied in order to search for the origin of its silicates and to explore a possible relationship between Tucson and the enstatite meteorites. All samples were analyzed with an electron microprobe. The silicate inclusions are described in terms of size and texture, and the silicate mineralogy, which is that of a highly reduced assemblage, is described. The bulk composition of the silicate inclusions is discussed. The results provide evidence of fast cooling. The textural and mineralogical data all point to the presence of a high temperature melt followed by rapid cooling and quenching. Several hypotheses for the origin of the Tucson are discussed, and it is concluded that the preferred hypothesis is that the meteorite formed by the high temperature impact mixing of a forsterite-enstatite silicate assemblage with Si-bearing metal, both having formed in a highly reduced environment.

Nehru, C. E.↗
NASA NTRS1981

Mineralogy, petrology, and trace element geochemistry of the Johnstown meteorite - A brecciated orthopyroxenite with siderophile and REE-rich components

The compositional and petrologic characteristics of the Johnstown meteorite show it to contain uncontaminated and unbrecciated orthopyroxenite clasts of cumulative origin that (1) must have undergone subsolidus recrystalization, (2) are parental to the brecciated matrix, and (3) show no evidence of a xenolithic, meteoritic contribution to the matrix except for contamination by the projectile which crushed it on impact. The trapped liquid was not introduced in the impact process. The variability of such trace elements as the light rare earth elements, and the presence of plagioclase and olivine in only one of the thin sections studied, demonstrates the heterogeneity of coarse-grained diogenites on a millimeter scale and the difficulty of obtaining representative samples of such meteorites. The data presented indicate that this meteorite is a monominct breccia.

Floran, R. J.↗
NASA NTRS1980

The nature and origin of ureilites

A theory of the origin of ureilites is presented based on mineralogical and petrological investigation of eight species including Kenna, Novo Urei, and Goalpara. The theory suggests that ureilites are primarily olivine-pigeonite cumulates crystallized from a silicate liquid which also contained suspended solid carbon phases. The carbon induced reduction of the melt and affected the ureilite mineral compositions. Petrofabric analyses show that mafic silicates are oriented in lineated and foliated patterns similar to cumulate rocks; strain rate of silicates suggests that ureilites were deformed after lithification by a mild tectonic stress and a moderate to severe shock.

Berkley, J. L.↗
NASA NTRS1980

Olivines and olivine coronas in mesosiderites

The paper presents a study of olivines and their surrounding coronas in mesosiderites texturally and compositionally using optical and microprobe methods. Olivine composition ranges from Fo(58-92) and shows no consistent pattern of distribution within and between mesosiderites; olivine occurs as large single crystals or as partially recrystallized mineral clasts, except for two lithic clasts. These are Emery and Vaca Muerta, and both are shock-modified olivine orthopyroxenites. Fine-grained coronas surround olivine, except for those in impact-melt group mesosiderites and those without tridymite in their matrices. Coronas consist largely of orthopyroxene, plagioclase, clinopyroxene, chromite, merillite, and ilmenite, and are similar to the matrix, but lack metal and tridymite. Texturally the innermost parts of the corona can be divided into three stages of development: (1) radiating acicular, (2) intermediate, and (3) granular.

Nehru, C. E.↗
NASA NTRS1980

Modal studies of mesosiderites and related achondrites, including the new mesosiderite ALHA 77219

The Antarctic meteorite ALHA 77219 is found to be a new mesosiderite. It contains about 25% metal + troilite (+ rust) and the brecciated silicate portion is dominated by orthopyroxene (En 68-71). These features, together with the presence of olivine surrounded by coronas, and abundant tridymite + phosphate conform to the characteristics of mesosiderites. A comparison of the modal abundances of minerals in 77219 with modes of 20 mesosiderites, 14 howardites, six basaltic eucrites, three feldspar cumulate eucrites, and one orthopyroxene cumulate eucrite shows that there are major differences between mesosiderites and howardites. These differences are described in detail.

Prinz, M.↗
NASA NTRS1980

Olivine clasts from mesosiderites and howardites - Clues to the nature of achondritic parent bodies

The compositional ranges of olivine clasts from mesosiderites and most clasts from howardites (FO90-55 and FO89-45 respectively) overlap. Only one clast in howardite Allan Hills A78006,9 (FO16) differs significantly. Differences in FeO/MnO in olivines from the two groups may be explained by different redox states of their source regions. Whether the two meteorite groups were derived from the same parent body is not clear, but the lack of Fe-rich eucritic clasts in mesosiderites together with the lack of tridymite-phosphate rich gabbros and basalts in howardites, suggests that different bodies are required since both meteorite groups are near-surface polymict breccias, which have probably sampled significant portions of their parent body surfaces.

Delaney, J. S.↗
NASA NTRS1980

Comparative petrology and origin of Governador Valadares and other nakhlites

The Governador Valadares is a cumulate augite achondrite showing many petrographic and geochemical similarities to the other known nakhlites, Nakhla and Lafayette. However, subtle differences in minor-element composition and textures suggest that each nakhlite is unique and probably represents a separate meteorite fall. Cumulus clinopyroxene compositions (En39FS23WO38) suggest crystallization from a common silica-saturated (tholeiite-like) liquid. Intercumulus mesostasis material shows evidence for a two-stage cooling history (slow, followed by quenching) and may represent highly fractionated, foreign pore liquid filtered into present nakhlites by compaction of lower-level cumulates.

Berkley, J. L.↗
NASA NTRS1979

Pyroxenes in Serra de Mage - Cooling history in comparison with Moama and Moore County

Thin sections and single grains of pyroxenes from the Serra de Mage feldspar cumulate eucrites were studied by X-ray crystallography, electron microprobe and optical techniques. It was concluded that the pyroxene crystallized as pigeonite. On cooling augite was exsolved along (001) and inverted to hypersthene, with exsolution of (100) augite from hypersthene during continued slow cooling. The estimated original bulk composition of the pigeonite pyroxene is Wo10En51Fs39. The compositional data, textural relations, and existence of P2 sub 1 ca hypersthene suggest very low cooling (about 0.0004 deg C/year) below 800 deg. The Serra de Mage augite lamellae were found to be as thick or thicker than those of Moore County and Moama meteorites.

Harlow, G. E.↗
NASA NTRS1979

Aubrites - Their origin and relationship to enstatite chondrites

A study of aubrites and their origin and relationship to enstatite chondrites is presented. Aubrites contain enstatite, plagioclase, diopside, and olivine; based on similarities in bulk chemistry of the silicate portions and inferred oxygen fugacity it is shown that E6 chondrites are the most likely parent material for chondrites. It is concluded that the addition of 10% plagioclase of An15 composition to the bulk composition of the silicate portion of the aubrites results in good agreement with that of E6 chondrites.

Watters, T. R.↗
NASA NTRS1978

The Chassigny meteorite - A cumulate dunite with hydrous amphibole-bearing melt inclusions

The Chassigny meteorite, an iron-rich dunite (Fo 68), is a moderately shocked olivine achondrite or chassignite with features indicative of a cumulate origin with some subsolidus annealing. The evidence that the meteorite experienced shock pressures of approximately 150-200 kbar is described. Kaersutitic amphibole, found only in melt inclusions, represents the first extraterrestrial occurence of hydrous amphibole and the first meteoritic amphibole type other than fluorichterite. Fractionation data indicate that Chassigny formed under relatively more oxidizing conditions than most other achondrites, which implies that its parental melt could not have been directly derived from a chondritic composition in a simple single-stage process. Similarities and differences with the Brachina meteorite, the only other meteorite of the Chassigny type, are considered.

Floran, R. J.↗
NASA NTRS1977

Studies of Brazilian meteorites. III - Origin and history of the Angra dos Reis achondrite

The mineral composition of the Angra dos Reis meteorite, which fell in 1869, is described. This achondrite contains phases reported in a meteorite for the first time. Petrofabric analysis shows that fassaite has a preferred orientation and lineation, which is interpreted as being due to cumulus processes, possibly the effect of post-depositional magmatic current flow or laminar flow of a crystalline mush. The mineral chemistry indicates crystallization from a highly silica-undersaturated melt at low pressure. Several aspects of the mineral composition are discussed with reference to the implications of crystallization conditions.

Prinz, M.↗
NASA NTRS1977

Comparison of lunar rocks and meteorites: Implications to histories of the moon and parent meteorite bodies

There are many similarities between lunar samples and stone meteorites. Lunar samples, especially from the highlands, indicate that they have been affected by complex and repeated impact processes. Similar complex and repeated impact processes have also been operative on the achondritic and chondritic meteorites. Similarities between lunar and meteoritic rocks are discussed as follows: (1) Monomict and polymict breccias occur in lunar rocks, as well as in achondritic and chondritic meteorites, having resulted from complex and repeated impact processes; (2) Chondrules are present in lunar meteorites, as well as in a few achondritic and most chondritic meteorites. They apparently crystallized spontaneously from molten highly supercooled droplets which may have formed from impact melts or, perhaps, volcanic processes (as well as from the solar nebula, in the case of meteoritic chondrites); (3) Lithic fragments vary from little modified (relative to the apparent original texture) to partly or completely melted and recrystallized lithic fragments. Their detailed study allows conclusions to be drawn about their parent rock types and their origin, thereby gaining insight into preimpact histories of lunar and meteoritic breccias. There is evidence that cumulate rocks were involved in the early history of both moon and parent meteorite bodies.

Prinz, M.↗