Scoriaceous, Porphyritic Olivine Basalt
Item
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Title
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Scoriaceous, Porphyritic Olivine Basalt
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Description
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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.
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Rights
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Lafayette College Department of Geology & Environmental Geosciences
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Identifier
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R-1837
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Date Created
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April 1, 2015
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Mediator
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Tamara Carley
