Graduation Date
Summer 2018
Document Type
Thesis
Program
Master of Science degree with a major in Environmental Systems, option Geology
Committee Chair Name
Brandon Browne
Committee Chair Affiliation
HSU Faculty or Staff
Second Committee Member Name
Jasper Oshun
Second Committee Member Affiliation
HSU Faculty or Staff
Third Committee Member Name
Melanie Michalak
Third Committee Member Affiliation
HSU Faculty or Staff
Fourth Committee Member Name
Mark Hemphill-Haley
Fourth Committee Member Affiliation
HSU Faculty or Staff
Subject Categories
Geology
Abstract
Quaternary mafic volcanism in the western Basin and Range and in the southeastern Sierra Nevada is largely controlled by extensional stresses that promote magma generation through decompression melting of the lithospheric and asthenospheric mantle. Where volcanism occurs in the Sierra Nevada, like at the Golden Trout Volcanic Field GTVF), the eruption rate, number of vents, and eruption volume is an order of magnitude less than at neighboring Basin and Range volcanic fields such as the Big Pine Volcanic Field (BPVF). To determine the factors that cause these differences in adjacent and contemporaneous volcanic fields, I sampled rocks from both fields and analyzed major and trace element compositions of olivine phenocrysts via electron microprobe, stable oxygen isotope compositions of olivine via laser fluorination, and whole-rock radiogenic isotope compositions via HR MC-ICP-MS. Major and trace element compositions between the GTVF and BPVF are overlapping with Fo values ranging from 67.61 to 88.77 and 77.72 to 88.13, respectively. δ18O values are higher at GTVF (5.680 to 6.520 ‰) than at BPVF (5.554 to 5.750 ‰). Whole rock 87Sr/86Sr and 143Nd/144Nd ratios at the GTVF range from 0.705420 to 0.706026 and 0.512492 to 0.512604 and overlap with values from BPVF and other regional volcanic fields. Similar mantle source compositions between the GTVF and BPVF indicate that differences in eruption rate, number of vents, and eruption volume are resultant from greater amounts of crustal contamination at GTVF. The presence of magmas with similar source compositions in and near the southern Sierra Nevada suggests that the regional extension characteristic of the Basin and Range has affected the southeastern Sierra Nevada block. Unfaulted crust in regionally extensional tectonic settings limits magma ascent, but doesn’t seem to inhibit magma genesis at depth.
Citation Style
GSA
Recommended Citation
Szymanski, Mark E., "Trace element and isotopic fingerprinting of olivine phenocrysts as recorders of magmatic processes in the Golden Trout Volcanic Field, Kern Plateau, CA" (2018). Cal Poly Humboldt theses and projects. 197.
https://digitalcommons.humboldt.edu/etd/197