Scoriaceous, Porphyritic Olivine Basalt

Item

Title
Scoriaceous, Porphyritic Olivine Basalt
Description
This sample exhibits a porphyritic texture in both hand sample and thin section. In hand sample, the dominant igneous features are olivine phenocrysts and vesicles. In thin section, the matrix that the olivine phenocrysts sit in is composed of microlites of plagioclase that exhibit lamellar twinning and compositional zoning. The vesicles show as clear gaps in plane light and black voids in cross-polarized light. This rock formed at depth where the Olivine phenocrysts had the time to accumulate but not enough time for plagioclase to form large crystals - the prophyritic texture is due to a quick cooling stage of the melt from eruption where the remaining melt stops crystallization.
Rights
Lafayette College Department of Geology & Environmental Geosciences
Identifier
R-1837
Date Created
April 1, 2015
Mediator
Tamara Carley

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