Abstract

Note: This paper is dedicated to Aaron and Elizabeth Waters on the occasion of Dr. Waters' retirement.

Clinopyroxenes in six rocks from the differentiation sequence gabbro-diorite-feldspathoidal and quartz syenites have been analyzed with the electron probe. Compositions of early-formed pyroxene in gabbro, diorite, monzodiorite, and feldspathoidal syenite fall in the range Ca42–47Mg36–43Fe13–18. The final pyroxene to crystallize in pulaskite was manganiferous soda augite (Ca43Mg20Fe37). In nordmarkite, manganiferous sodic ferrohedenbergite (Ca42Mg8Fe50) was followed by manganiferous aegirine-augite. Relatively low PQ, apparently prevailed throughout the course of pyroxene crystallization.

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