Bull. Soc. fr. Minéral. Cristallogr.
(1977), 100, 315-324.
Crystal structure control in trace element partition between crystal and magma (*)
by Yoshito MATSUI (*), Naoki ONUMA (2), Hiroshi NAGASAWA (3), Hideo HIGUCHI (4)
and Shohei BANNO (5),
(1) Institute for Thermal Spring Research, Okayama University, Misasa, Tottori-ken 682-02.
(2) Institute of Chemistry, The University of Tsukuba, Niihari-gun, Ibaraki-ken 300-31. (3) Department of Chemistry, Faculty of Science, Gakushuin University, Mejiro, Toshima-ku, Tokyo 171. (4) Japan Chemical Analysis Center, Funado, Itabashi-ku, Tokyo 174.
(5) Department of Earth Sciences, Faculty of Science, Kaioazawa. University, Kanazawa, Ishikawa ken 920. Japan.
Influence de la structure du cristal sur le coefficient de partage d'éléments en trace, entre cristal et magma ,
Introduction
How major and trace elements are distributed between minerals and magma has been one of the most fundamental problem in solid-earth geochemistry since the age of V. M. Goldschmidt. He summarized the modes of incorporation of minor ions into minerals in his well-known rules in terms of camouflage, cap¬ ture and admission, recognizing the dominant role of ionic radii of the relevant elements (Goldschmidt, 1937 ; see also Mason, 1966, p. 132).
Since his time there has been much discussion of this problem for and against the Goldschmidt rules. The fractionation trends of most elements in magma-tic processes became clear with accumulation of data on the abundances of elements in various rock types. Most of previous studies, however, have been simply of the character of ' the geochemistry of certain ele¬ ment (s) ', mainly restricted by difficulties in chemi¬ cal analysis, until about 1967. The present authors became aware that we do not necessarily need the
(*) Dedicated to the memory of the late Professor Eiiti Minami.
accumulation of wast amount of simple analytical data, but do need data of high quality on the contents of as many elements as possible in coexisting phases on a rather limited number of selected volcanic rock specimens.
The above principle had lead us to start a project which we call «all-ium project ». Onuma et al. (1968) determined the partition coefficients of twenty-one trace elements between phenocryst pyroxenes (au¬ gite and bronzite) and groundmass in an alkali-oli-vine basalt by neutron activation analysis. They plot¬ ted the partition coefficients, regardless of whether the element was a major one (data on major elements had been available) or a trace one, against the Gold¬ schmidt ionic radii (Goldschmidt et al., 1926), and first constructed the novel «partition coefficient versus ionic radius diagrams » (abbreviated to «PC-IR diagrams » hereafter). The shapes of the sub-parallel curves for elements of each valency indicated stron¬ gly that the crystal structure of the phenocryst plays a dominant rôle in determining the partition coeffi¬ cient patterns between phenocryst and groundmass. Independently, Schnetzler and Philpotts (1968) pro-
