Abstract
Variations in mineralogy and compositions of principal rock-forming minerals serve as an indicator of basaltic magma differentiation. Features of the composition of olivine, pyroxenes, plagioclase, spinel group minerals, micas, and ilmenite are described in Sect. 4.1. The compositions of olivine and plagioclase in layered intrusions vary from forsterite to fayalite and from albite to anorthite, respectively. Pyroxene is present as augite of the varying composition; pigeonite and orthopyroxene are less abundant. Minerals of the spinel group are represented by a series of spinel, chromite, and magnetite. Chromespinellides form accessory impregnations and accumulations in gabbrodolerites and pegmatoids. Micas occur as phlogopite–annite with the Fe/(Fe + Mg) ratio ranging from 1 to 90 at%.
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