About the Cover
This clinopyroxene is from the Triassic greenstone of the Chulitna Terrane in south-central Alaska, interpreted to be the accreted remnant of a rifted arc. Photo by Maureen Feineman. Fresh clinopyroxenes or clinopyroxene cores are often preserved in otherwise heavily altered greenstones formed from ancient basaltic protoliths. These phenocrysts provide an opportunity to see through the compositional changes incurred by the rock during greenstone alteration, back to the original basalt composition. See related article by Gilman et al. (v. 121, no. 7/8, p. 979-991.)
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