Date of Award
5-2025
Document Type
Thesis
Degree Name
Master of Science in Geology
Department
Geological Sciences
First Reader/Committee Chair
Codi Lazar, Ph.D.
Abstract
Serpentinites are metamorphic rocks typically produced by hydrating mantle peridotites to form assemblages containing one or more serpentine minerals. They occur in various tectonic and geologic settings, such as submarine hydrothermal systems, ophiolite sequences, and the forearc mantle. Serpentinites are associated with highly reduced conditions, as indicated by low oxygen fugacity (ƒO₂) values. Previous investigations suggest that oxygen fugacity varies with tectonic setting due to differences in environmental conditions. To test this hypothesis, we analyzed serpentinites from a wide variety of tectonic settings in western North America: The New Idria forearc diapir (CA), Canyon Mountain Island arc complex (OR), Josephine ophiolite (OR), and the Franciscan accretionary prism complex (CA) (Fig. 1). We present petrographic and geochemical analyses of serpentinites from each setting and determine oxidation states using phase equilibria, converting aH₂ values to ∆log ƒO₂ relative to QFM. The results show that ƒO₂ values overlap across all tectonic settings, indicating that oxygen fugacity alone cannot be used to determine a serpentinite’s tectonic origin based on accessory mineral assemblages.
Recommended Citation
Seymour, Bryan H.T., "A MINERALOGICAL AND GEOCHEMICAL INVESTIGATION OF THE INFLUENCE OF TECTONIC SETTING ON ACCESSORY MINERAL ASSEMBLAGES IN SERPENTINITES ALONG THE WESTERN NORTH AMERICAN MARGINS" (2025). Electronic Theses, Projects, and Dissertations. 2176.
https://scholarworks.lib.csusb.edu/etd/2176