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Harlow, G. E.

Publications and source records attributed to Harlow, G. E..

10 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Mineralogical comparison of antarctic and non-antarctic HED (howardites-eucrites-diogenites) achondrites

Mineralogical examination of thin sections of non-Antarctic and Antarctic HED (howardite, eucrite, diogenite) achondrites indicates that they contain a variety of lithic components. Some of these components occur both as monomict meteorites and as clasts in polymict meteorites, whereas others occur only as clasts in some polymict breccias. The components may be classified by the degree of homogenization of the pyroxene present. In order of increasing homogeneity these are: (1) Y-75011-type basalt clasts; (2) Pasamonte; (3) Y-790266-type clasts; (4) Stannern and Nuevo Laredo; (5) Juvinas and Haraiya; and (6) Ibitira. Type 1 has been least modified by post-igneous thermal annealing, while types 5 and 6 were thoroughly metamorphosed. Three types of cumulate eucrites are recognized and are believed to represent (a) cumulates from thick lava flows or layered intrusions; (b) lunar highlands type crust; and (c) differentiation products of diogenitic magmas.

Takeda, H.↗
NASA NTRS1983

The nomenclature of polymict basaltic achondrites

The system of nomenclature for basaltic achondrite meteorites is discussed, and new classification criteria are proposed. Under the new system, all achondrites are divided intno the broad groupings 'monomict' and 'polymict' by the number of lithologies present. The monomicts are classified structurally as brecciated or unbreccciated and as eucrites, diogenites, or cumulate eucrites. The polymicts are classified using an arbitrary mineral-chemical standard based on the percentage content of diogenite (magnesium orthopyroxenite): diogenites have more than 90 percent, eucrites have less than 10 percent, and all other polymicts area howardites. Tables listing all known achondrites by classification are provided.

Delaney, J. S.↗
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 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

Clouding of pyroxene and plagioclase in eucrites - Implications for post-crystallization processing

The clouding of pyroxene and plagioclase in the basaltic eucrites ALHA 77302, Juvinas, Pasamonte, and Stannern, is caused by finely disseminated inclusions. This clouding is interpreted to be the result of exsolution of minor components which became incompatible and crystallized on microfractures and other nucleation sites during postbrecciation metamorphism. The phases found in clouding require reduction of silicate FeO to metallic Fe in both pyroxene and plagioclase and possible redox of Cr(2+) to Cr(3+) in pyroxene. The assemblage of coexisting phases that make up clouding record conditions of T approximately equal to 900 C and f(O2) of 10 to the -16th to 10 to the -18th during slow cooling. Thus, clouding can be a useful indicator of postcrystallization conditions.

Harlow, G. E.↗
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.↗