Title
The Chemical Evolution of Oceanic and Continental Lithosphere: Case Studies in the US Cordillera
Date of Award:
8-2012
Document Type:
Dissertation
Degree Name:
Doctor of Philosophy (PhD)
Department:
Geology
Committee Chair(s)
John W. Shervals
Committee
John W. Shervals
Committee
Barry B. Hanan
Committee
Carol M. Dehler
Committee
Anthony R. Lowry
Committee
James P. Evans
Committee
Keith D. Putrika
Abstract
Investigations into ophiolite from California demonstrated that these ultramafic rocks formed within the mantle wedge of a subduction zone. Fore-arc locales are dominated by highly refractory peridotite, formed by hydrous-fractional partial melting that began in the garnet stability field and ended in the spinel stability field. These ophiolites also displayed enriched fluid-mobile element concentrations. Based on melt models, these elements should have extremely low concentrations, yet all pyroxenes display enriched compositions. A new algorithm was derived to model this fluid enrichment process, which represents the total addition of material to the mantle wedge source region and can be applied to any refractory mantle peridotite that has been modified by melt extraction and/or metasomatism. Investigations into the interaction of a mantle plume with continental lithosphere demonstrated that Yellowstone-Snake River Plain olivine tholeiites are compatible with genesis from a deep-seated mantle plume and were modeled via mixing of three components. The variable age, thickness, and composition of North American lithosphere guide this process. Drill core near Twin Falls, ID was examined to assess (1) the chemical evolution of olivine tholeiite, (2) how basalt evolves in continental settings, and (3) the dominant fractionation process, e.g., fractional crystallization, Raleigh fractional crystallization, or assimilation fractional crystallization.
Checksum
6db1dc95fda68f7b417f5bb398ceced0
Recommended Citation
Jean, Marlon Mauricio, "The Chemical Evolution of Oceanic and Continental Lithosphere: Case Studies in the US Cordillera" (2012). All Graduate Theses and Dissertations. 1281.
https://digitalcommons.usu.edu/etd/1281
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Comments
This work made publicly available electronically on July 30, 2012.