Ringing Rocks Sample 14
Item
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Title
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Ringing Rocks Sample 14
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Description
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During our field trip to Ringing Rocks on April 9, 2015 we took multiple samples and field notes from the historic diabase from this location. This hand sample was taken from the boulder field margin and a sample was then cut to create a thin section of the sample. The sample displays many mafic minerals contained within it, typical to an early formed magma. The sample was taken from 40.563272N/ 75.129980W.
A possible hypothesis for this sample is that it was within the location of the bottom of the intruding magma sill. This is due to the abundance of large olivine phenocryts within the sample. These olivine crystals likely collected at the bottom of the sill of magma diabase due to fractional crystallization. The olivine crystals formed early within the stages of the melt cooling and likely fell to the base of the magma chamber within the sill. This would cause large amounts of olivine crystals to be present within the hand sample and the thin section. Within the thin section, olivine crystals show fracturing and inter-growths of plagioclase feldspar and hornblende. This likely describes this portion of the sill was uplifted, releasing pressure quickly, and resulted in cracks in the olivine phenocrysts as well as smaller growths of plagioclase feldspars and pyroxene microlites. However without further samples of multiple depths and locations of the diabase sill, it cannot be determined that this specific sequence of events occurred.
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Subject
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Ringing Rocks Field Trip
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Creator
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Ryan Sanders
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Source
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Ringing Rocks
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Date
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4/9/15
