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dc.contributor.advisor Wiegand, Peter en Devlahovich, Vincent A. en 2016-05-20T21:26:37Z en 2016-05-20T21:26:37Z en 2001 en 2001-06 en
dc.identifier.uri en
dc.description Includes bibliographical references (leaves 42-46) en
dc.description California State University, Northridge. Department of Geological Sciences. en
dc.description.abstract Igneous rocks are associated with exposures of San Onofre Breccia (SOB) on Santa Cruz Island as clasts and on Santa Catalina Island as sills and dikes. Samples collected from these two areas were analyzed for major oxides, trace elements, and isotope ratios. Santa Cruz Island SOB clasts have a fine-grained, holocrystalline, phorphyritic texture and exhibit minimal alteration. Fresh and unaltered plagioclase phenocrysts make up 20 to 25% of the rocks, and small amounts of biotite are found in most samples. Santa Catalina Island SOB samples have a fine-grained and altered or recrystallized matri x. Altered plagioclase phenocrysts are present in small amounts (generally 1 to 5%) along with quartz phenocrysts and calcite; chlorite is found in a few samples whereas biotite is lacking. Santa Cruz SOB clasts consist of low-K rhyolite and exhibit two compositional geochemical groupings Santa Catalina SOB samples range from medium-K basaltic andesite to rhyolite with most samples classified as dacite. Compared to Santa Cruz clasts, Santa Catalina samples exhibit greater trace-element enrichment and less fractionated REE and spider diagram patterns. Based largely on geochemical evidence, it is concluded that the Santa Cruz Island SOB clasts may be related to clasts in the overlying Blanca Formation, but differ significantly from Santa Cruz Island Volcanics and from Santa Catalina Island SOB samples. Additionally, it is concluded that the Santa Catalina Island SOB samples may be related to the overlying Santa Catalina Island Volcanics. Isotopic data suggest that these two occurrences of Miocene volcanic rocks were generated, after subduction of the Farallon plate had ceased, by decompression melting of a depleted mantle source, and subsequent crystal fractionation and interaction of these magmas with overlying, previously emplaced Catalina schist led to the unique geochemical signatures found in these samples. en
dc.description.statementofresponsibility by Vincent A Devlahovich en
dc.format application/pdf en
dc.format.extent viii, 47 pages en
dc.language.iso en en
dc.publisher California State University, Northridge en
dc.rights.uri en
dc.subject.other Dissertations, Academic -- CSUN -- Geology. en
dc.title Miocene igneous rocks associated with the San Onofre Breccia, Santa Cruz and Santa Catalina Islands, California en
dc.type Thesis en 2016-05-20T21:26:37Z en
dc.contributor.department Geological Sciences en M.S. en
dc.contributor.committeemember Howard, Robert B. en
dc.contributor.committeemember Dole, Jim W. en
dc.contributor.committeeMember Howard, Robert B. en
dc.contributor.committeeMember Dole, Jim W. en
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