Eugene Jarosewich

Petrogenesis of the Elephant Moraine A79001 meteorite Multiple magma pulses on the shergottite parent body

Abstract The EETA 79001 achondrite consists of two distinct igneous lithologies joined along a planar, non-brecciated contact. Both are basaltic rocks composed primarily of pigeonite, augite, and maskelynite, but one contains zoned megacrysts of olivine, orthopyroxene, and chromite that represent disaggregated xenoliths of harzburzite. Both lithologies probably formed from successive volcanic flows or multiple injections of magma into a small, shallow chamber. Many similarities between the two virtually synchronous magmas suggest that they are related. Possible mechanisms to explain their differences involve varying degrees of assimilation, fractionation from similar parental magmas, or partial melting of a similar source peridotite; of these, assimilation of the observed megacryst assemblage seems most plausible. However, some isotopic contamination may be required in any of these petrogenetic models. The meteorite has suffered extensive shock metamorphism and localized melting during a large impact event that probably excavated and liberated it from its parent body. Both basaltic lithologies and the inferred ultramafic protolith of the megacryst assemblage are petrologically similar to other members of the shergottite group, and all may have been derived from a volcanic-plutonic complex on a planetary body.

Midinfrared (2.5–13.5 μm) reflectance spectra of powdered stony meteorites

Abstract Reflectance spectra (2.5 to 13.5 μm) of 60 powdered meteorite samples representing 50 different meteorites are presented for comparison with spectral measurements of asteroids. Powdered samples were used as analogues of asteroidal regoliths. These spectra show that most powdered meteorite samples have undergone alteration, even if only exposed to water vapor in the air, and many have been contaminated by volatile hydrocarbons characterized by absorption bands near 3.45 μm. In contrast, primary macromolecular hydrocarbons do not display the 3.45-μm bands, or, in fact, any other detectable spectral features in these reflectance spectra. However, powdered meteorites display a wide variety of other spectral features that can be used for their identification. These include residual reststrahlen features, which occur as reflectance peaks, absorption bands due to overtone/combination tone bands, which occur as reflectance troughs, and the Christiansen feature, which also occurs as a trough in reflectance. The most prominent reststrahlen peaks are those of olivine and pyroxene, and the wavelength position of the olivine features is sensitive to the Mg/Fe ratio. Olivine and pyroxene also show strong overtone/combination tone absorption bands that shift position with the Mg/Fe ratio, and calcite can be identified in the spectra of some carbonaceous chondrites from such overtone/combination tone bands. These spectral features can be used independently to help determine mineralogy and meteorite type, but using the entire spectrum in a digital search library is preferred for successfull identification. The spectral effect of the vacuum environment should be relatively small for meteorites compared to that found in previous work for granites, but confident interpretation of the spectra of asteroids will require a better understanding of the effects of the space environment on meteorite spectra and of the spectral mixing model for meteorite minerals.

The mineralogy of ordinary chondrites and implications for asteroid spectrophotometry

Abstract The normative mineralogies of 94 ordinary chondrites have been calculated from high-quality bulk chemical analyses. Relative proportions of olivine, orthopyroxene, and metal are more variable within the H, L, and LL classes than has been recognized previously. Mineralogy within each chondrite class varies systematically with oxidation state. These data have important implications for the design of reflectance spectroscopy studies that match asteroid and meteorite spectral features and for quantitative spectral interpretations of asteroids. They also provide a tool with which to predict mineral abundances in unsampled asteroids that formed under different redox conditions.

St. Peter and St. Paul Rocks: A High-Temperature, Mantle-Derived Intrusion

St. Pauls Rocks, often postulated to be an exposure of the suboceanic mantle, consists of a wider variety of rocks than previously recognized. These perhaps crystallized at different mantle levels, and were subsequently incorporated and mylonitized in a hot but solid intrusion.

Chemical analyses of ten stony meteorites

Abstract A group of stony meteorites, mainly unequilibrated chondrites ( Dodd and Van Schmus , 1965), has been analysed chemically. The chemical analyses of ten meteorites are given in this paper. Detailed studies of the petrology and mineralogy of these meteorites are in progress.

Smithsonian Microbeam Standards.

This is a short history of the Smithsonian Microbeam Standards; their sources, selection, preparation, and analyses. Fifty-eight minerals, natural glasses, and synthetic samples have been characterized in the past 25 years. During that time, over 750 requests were received for approximately 11 000 individual samples. These reference samples are referred to as the Smithsonian Microbeam Standards.

Chemical analyses with notes on one mesosiderite and seven chondrites.

Abstract Chemical analyses, with short notes on mineralogy and chemical procedures, are given for the bronzite chondrites Allegan and Guarena; the hypersthene chondrites Rupota, Cherokee Springs and Saint Severin; the carbonaceous chondrite Efremovka; the enstatite chondrite Pillistfer; and the mesosiderite Patwar.

Chondrules: First Occurrence in an Iron Meteorite

Complete chondrules and fragments of chondrules have been found within silicate inclusions from the octahedrite iron meteorite Netschaevo. The bulk chemical composition, mineralogy, and mineral chemistry indicate that this chondritic material has properties intermediate between those of the H-group chondrites and those of the enstatite chondrites.

Chemical analyses of seven stony meteorites and one iron with silicate inclusions

Abstract A group of stony meteorites: Bununu, Cumberland Falls (Black Chondr. Incl.), Forest Vale, Goodland, Grady (1937), Leedey, Mezo-Madaras, and one silicate-rich iron meteorite, Woodbine, have been chemically analysed. The results of these analyses are presented in this paper.

Chemical studies of L-chondrites—I. A study of possible chemical sub-groups

Radiochemical neutron activation analysis of Ag, As, Au, Bi, Co, Cs, Ga, In, Rb, Sb, Te, Tl and Zn and major element data in 14 L4-6 and 3 LL5 chondrites indicates that the L-group is unusually variable and may represent at least 2 sub-groups differing in formation history. Chemical trends in the S/Fe-rich sub-group support textural evidence indicating late loss of a shock-formed Fe-Ni-S melt; the S/Fe-poor sub-group seemingly reflects nebular fractionation only. Highly mobile In and Zn apparently reflect shock-induced loss from L-chondrites. Data for L5 chondrites suggest higher formation temperatures and/or degrees of shock than for LL5 chondrites.