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Insight into the Evolving Composition of Augustine Volcano's Source Magma from a Low-K Dacite

Thomas, Christian
http://orcid.org/0000-0001-6330-5854
http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors1536081965599329

Abstract Details

2018, Bachelor of Science (BS), Ohio University, Geological Sciences.
Augustine Volcano, located in southern Alaska, has erupted a wide compositional variety of volcanic rocks over its ~26,000 year lifespan. We performed an investigation of the mineralogy and petrology of the low-K dacite (LKD), the oldest yet-unstudied unit in the Augustine tephrostratigraphic succession, with the goal of creating a hypothesis of how the unit formed, as well as finding the unit's relationship to other ancient Augustine tephras. Our work was based on examination of hand samples, grain mounts, and thin sections of the LKD, the latter examined with both petrographic microscopes and with the electron microprobe at the American Museum of Natural History. We found a mineral assemblage in the LKD including plagioclase, calcic amphiboles, cummingtonite, magnetite, and ilmenite. Modeled values for the temperature, pressure, oxygen fugacity, and water content of the LKD's parent melt led us to the conclusion that the unit was derived from mixing of a rhyolitic parent magma similar to that of the ~30 m thick rhyolite erupted by Augustine in the Pleistocene, together with deeply-sourced mafic material of a similar geochemical character to the mafic component of the high-P dacite hypothesized by other research. Further work is needed to fully characterize this unit, as well as those above it in the Augustine tephrostratigraphic column, in order to arrive at a complete understanding of the relationship between ancient and modern Augustine tephras.
Patricia Nadeau, Dr. (Advisor)
Keith Milam, Dr. (Committee Member)
Alycia Stigall, Dr. (Committee Member)
57 p.
Earth; Geological; Geology; Mineralogy; Petrology
geology; volcanology, dacite; calcic amphibole; thermometry; petrology; Augustine Volcano; low-K dacite; zoning; zoned plagioclase; magnetite-ilmenite;

Recommended Citations

Citations

  • Thomas, C. (2018). Insight into the Evolving Composition of Augustine Volcano's Source Magma from a Low-K Dacite [Undergraduate thesis, Ohio University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors1536081965599329

    APA Style (7th edition)

  • Thomas, Christian. Insight into the Evolving Composition of Augustine Volcano's Source Magma from a Low-K Dacite. 2018. Ohio University, Undergraduate thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors1536081965599329.

    MLA Style (8th edition)

  • Thomas, Christian. "Insight into the Evolving Composition of Augustine Volcano's Source Magma from a Low-K Dacite." Undergraduate thesis, Ohio University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors1536081965599329

    Chicago Manual of Style (17th edition)

ouhonors1536081965599329
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This open access ETD is published by Ohio University Honors Tutorial College and OhioLINK.