Garnetiferous olivine metagabbro




This specimen is typical of the olivine metagabbros that occur throughout the Adirondacks. These rocks are of great petrologic interest for they contain classic examples of garnet coronas and spinel-clouded plagioclase. Note the preservation of ophitic and sub-ophitic igneous textures even though these rocks have experienced granulite facies conditions. A magnificent example of transition to eclogite facies.

The following information is from the original OCR document: Detailed reactions accounting for both metamorphic assemblages and textures are developed in McLelland and Whitney, "A Generalized Garnet-Forming Reaction for Metamorphic Rocks in the Adirondacks," 1980, Contributions to Mineralogy and Petrology, v.72, p. 111-122. Explanations for a number of metamorphic textures in these rocks can be found in McLelland and Whitney, "Compositional Controls On Spinel and Garnet Formation in Plagioclase of Olivine Metagabbros," 1980, Contributions to Mineralogy and Petrology.
The first 2 thin sections show a plagioclase lath and a garnet with plagioclase and olivine surrounding it. The second 2 thin sections show a garnet with plagioclase corona and olivine crystals surrounding the garnet.




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Purchased from Western Minerals Inc.

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