Survey and evaluation of eucrite bulk compositions

Abstract

Abstract-The purpose of this survey is to establish reference bulk elemental abundances for the eucrites and thereby provide the basis to test core formation models as well as partial melting, fractional crystallization and magma ocean theories for the eucrite parent body. In order to evaluate bulk elemental abundances for the eucrites, 296 peer-reviewed articles, monographs, theses or books and 143 abstracts dating from 1938 to 1997 were surveyed. Of the 10 1 eucrites having at least one set of elemental abundance analyses reported in the literature, 20 were selected for in-depth examination. The selection criteria of our sample were based on the total number of analyses available for a given eucrite and the total number of elements for which data exist. The mean bulk elemental abundance, la standard deviation, and the percent deviation were calculated for each element in a given eucrite. In order to evaluate the quality of the mean abundances, the elements were then grouped according to availability of data and percent deviations. Possible reasons for the different deviations in the different groups are briefly discussed. From the major element abundances, the normative (CIPW) composition, the molar compositions of pyroxene, olivine and plagioclase, and the bulk densities were calculated and compared to petrographic observations. The calculated norms for the noncumulates agree well with the observations while the norms for the cumulates do not. Possible reasons for this are discussed. Unfortunately, analyses of many elements are poorly represented in the literature and many bulk analyses suffer from unacceptable levels of uncertainty. Therefore, future work requires bulk elemental analyses for some of the more poorly characterized elements in eucrites, especially those of key elements used for planetary modeling.

Formation of vesicles in asteroidal basaltic meteorites

“…The physical properties of the melt are additional input parameters. The bulk composition of Ibitira [19] was input to the MELTS [20,21] program to calculate a liquidus temperature (1185°C at a depth of 60 km) and into formulations of [22] to calculate the viscosity (16.1 Pa s) and density (2840 kg/m 3 ) of the melt. We note that the relatively low abundance of bubbles in the magma would not substantially change its bulk viscosity.…”

Oxygen isotopic constraints on the origin and parent bodies of eucrites, diogenites, and howardites

“…Plagioclase compositions are unusually high in Mg and Fe. The bulk CaO in NWA 1240 is low for eucrites (8.1 wt.% vs. 8.4-11.1 in eucrites), and FeO is high for cumulate eucrites (20.2 vs. 12-17) (Kitts and Lodders, 1998).…”

“…Unlike most eucrites, which have been metamorphosed and contain compositionally equilibrated pyroxenes, Pasamonte contains pyroxenes with extensive igneous Mg/Fe zoning and it is classed as a rare type 2 eucrite on the Takeda-Graham type 1-6 scale of metamorphism (Takeda and Graham, 1991 The composition of Pasamonte does not appear abnormal for a eucrite (Kitts and Lodders, 1998), although Ni and Ir concentrations are at the high end of the eucrite range. The mean Fe/Mn ratio in Pasamonte's pyroxene (29) lies at the low end of the eucrite range (28-40; Lentz et al, 2007), and its chromite composition appears to be exceptional with very high Al 2 O 3 (18 wt.% vs. 7-9% in other eucrites) and very low TiO 2 (1.4 wt.% vs 3-6% in eucrites) (Bunch and Keil, 1971;Mittlefehldt et al, 1998).…”

Iron isotope fractionation in planetary crusts

“…Redox proxies indicate that angrites probably formed in a relatively oxidized environment (IW+1 to +2; Jurewicz et al, 1991Jurewicz et al, , 1993McKay et al, 1994), even though the exact redox conditions are difficult to quantify. Dauphas et al (2009a) Kitts and Lodders (1998). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)…”