Thesis
Spatiotemporal evolution of the Lava Creek tuff magma chamber in Yellowstone National Park: eruption triggering mechanisms from major and trace element zoning in feldspar
Washington State University
Master of Science (MS), Washington State University
2015
Handle:
https://hdl.handle.net/2376/101496
Abstract
The Lava Creek Tuff eruption of the Yellowstone Plateau Volcanic Field occurred about 640,000 years ago and involved the evacuation of ~1000km3 of pyroclastic material from the magma chamber. Comprised of members A and B, the Lava Creek Tuff is a chemically zoned high silica rhyolite system that compositionally resets between emplacements of members. Whole rock incompatible trace element concentrations reconstruct the geochemical stratigraphy of the pre-eruptive Lava Creek Tuff chamber. The results define compositional zonation trends that clearly distinguish between members A and B, as well as identification of the lower and upper sub units of each member (e.g., upper A Zr=185-300ppm, Nb=49-51ppm; lower A Zr=162-166ppm, Nb =67-74ppm; upper B Zr=280-365ppm, Nb=57-62ppm; lower B Zr=170- 190ppm, Nb =53-69ppm). Such signatures could denote the presence or absence of the accessory mineral phases, chevkinite, allanite and zircon. Chevkinite and allanite are abundant in member A, and zircon varies in abundance between the subunits of both member A and B. Evidence that compositional zonation within the Lava Creek Tuff was likely not the result of fractional crystallization is suggested by modeled whole rock trace element concentrations derived from the Rayleigh fractionation equation, which do not produce trends that reflect the arrays produced by measured concentrations. The chemistry of individual feldspar phenocrysts acquired by electron microprobe and laser ablation analyses help to further characterize the subunits of members A and B in the pre-eruptive magma chamber. Sanidine phenocrysts from the upper and lower parts of members A and B range between Or46 - Or57 and exhibit rimward enrichment of compatible trace elements such as Ba and Sr. Rimward enrichment of compatible trace elements such as Ba and Sr suggest a role for mafic replenishment, however, variation of Sc vs. Th whole rock concentrations within the Lava Creek Tuff do not produce trends that intersect with Yellowstone basalt concentrations. This suggests that injections of mafic material did not occur rapidly enough or in large enough volumes to trigger the eruption of the Lava Creek Tuff.
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Details
- Title
- Spatiotemporal evolution of the Lava Creek tuff magma chamber in Yellowstone National Park
- Creators
- Jennipher Constantine Von Stauffenberg
- Contributors
- Peter B. Larson (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Environment, School of the (CAHNRS)
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525119901842
- Language
- English
- Resource Type
- Thesis