Abstract

Multiple amphibole assemblages have been identified in a variety of metamorphic rocks. Recent studies have shown that three- and four-amphibole assemblages commonly contain anthophyllite, gedrite, hornblende, actinolite, and cummingtonite in various combinations (e.g., Robinson and Jaffe, 1969; Robinson et al., 1969; Stout, 1971; Spear, 1980, 1982; reviewed by Robinson et al., 1982). Although it has been suggested on the basis of amphibole crystal chemistry that assemblages containing five amphiboles might occur (e.g., Robinson et al., 1982), no such occurrences have been reported. In the course of a transmission and analytical electron-microscope (tem-aem) study of exsolution microstructures in coexisting amphiboles from New England blueschists, we have now identified a five-amphibole assemblage consisting of glau-cophane, cummingtonite, winchite, actinolite, and hornblende existing in a single composite grain. This amphibole assemblage differs from those mentioned above in that it contains no orthoamphiboles and contains representative compositions from each of the four major amphibole subgroups of Leake (1978). The purpose of this note is to describe the mode of occurrence and composition for each of the five amphiboles.

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