Two Pyroxene-spinel metagabbro

Two Pyroxene-spinel metagabbro

AD-19

The locality near Northville, NY represents the only example of this assemblage that has been encountered to date (1980) in the Adirondacks. The original lithology is that of a typical olivine metagabbro. During granulite facies metamorphism, reactions produced coronas consisting of orthopyroxene rims on olivine and spinel-clinopyroxene symplectites. Amphibole-spinel coronas also occur. These assemblages appear to represent lower pressure conditions than prevailed during the formation of the garnet-bearing assemblages represented by AD-16.

The following information is from the original OCR document: The mineralogy and textural features of these metagabbros are discussed in McLelland and Whitney, 1980, Contributions to Mineralogy and Petrology, v.72, p.111, specimen 17 and Whitney and McLelland, "Origin of Coronas in Olivine Metagabbros of the Adirondack Mountains, NY," 1973, Contributions to Mineralogy and Petrology, v. 39, p.81-98. The specimen you receive may be somewhat smaller than the regular specimens. Dr. James McLelland collected this material especially for this suite-and in 100° temperature. Thank you, Jim.

Thin section shows augite, spinel and plagioclase.

1980

Western Minerals Inc.

Adirondack Highlands-collected from the first high hill just southwest of the intersection of NY Route 30 and Benson Rd., approximately 2 miles northwest of Northville, NY.

Precambrian

Purchased from Western Minerals Inc.

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