Aspects of the chemistry of some stony meteorites

McCarthy, T S

Aspects of the chemistry of some stony meteorites

Thesis / Dissertation

1971

Abstract

[pg 20,67 missing] Ten eucrites, four howardites, three enstatite achondrites, eight HL chondrites, the one known chassignite and a chondrite inclusion from the Cumberland Falls achondrite have been analysed for major, minor and some trace elements (viz. Fe, Mn, Ca, Cr, P, Si, Al, Mg, Na, K, Sr, Zr, Y, Ba and Ni) using X-ray fluoresence analysis. A fusion technique was used to determine the more abundant elements, while trace constituents were determined on powdered samples. The data obtained have been critically examined from the point of view of both precision and accuracy, and found to be of a high standard for most elements. Inter-element relationships amongst the diogenites, howardites and eucrites suggest that two distinct processes were involved in the genesis of these meteorites. Theories for the origin of these meteorites have been examined in the light of these inter-element relationships. It is concluded that mixing of diogenitic and eucritic material was responsible for the formation of howardites, while diogenites and eucrites appear to have been formed by processes of igneous differentiation from a single parent magma. The unique achondrite Chassigny may also be a product of this process. Some speculations concerning the composition of the parent; material from which these meteorite types crystallized are presented. The enstatite achondrites are apparently unrelated to the previously mentioned meteorite types. They do, however, show close affinities with the enstatito chondrites. It would appear that the two types are not related by igneous differentiation, but were probably formed by the same processes. The chondrite fragment removed from the Cumberland Falls achondrite has a composition which suggests that it is a member of the genetic sequence represented by enstatite chondrites and achondrites. The Vigarano and Ornans sub-types of the HL chondrites were observed to exhibit slight but distinct differences in bulk composition in the form of higher Ca and Al abundances in the Vigarano sub-type. Superimposed on these differences are more dramatic chemical differences which appear to be associated with the recrystallization which some of these meteorites have undergone. These differences include loss of alkali metals, Ca and Al.

Keywords

Geological Sciences

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