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dc.contributor.authorThomas, Jay Bradley Jr.en_US
dc.date.accessioned2014-03-14T20:51:50Z
dc.date.available2014-03-14T20:51:50Z
dc.date.issued1998-05-18en_US
dc.identifier.otheretd-52598-142754en_US
dc.identifier.urihttp://hdl.handle.net/10919/36795
dc.description.abstractThe quartz dioritic Quottoon Igneous Complex (QIC) is a major Paleogene (65-56 Ma) magmatic body in NW British Columbia and SE Alaska that was emplaced along the Coast shear zone (CSZ). The QIC contains two different igneous suites that provide information about source regions, magmatic processes and evolving tectonic regimes that changed from a dominantly convergent to a dominantly strike-slip regime between 65 to 55 Ma. Heterogeneous suite I rocks (e. g. along Steamer Passage) have a pervasive solid-state fabric, abundant mafic enclaves and dikes, metasedimentary screens, and variable color indices (25-50). The homogeneous suite II rocks (e. g. along Quottoon Inlet) have a weak (to absent) fabric developed in the magmatic state (aligned feldspars, melt filled shears), and more uniform color indices (24-34) than in suite I. Suite I rocks have Sr concentrations <750 ppm, avg. LaN/YbN = 10.4, and initial 87Sr/86Sr ratios that range from 0.70513 to 0.70717. The suite II rocks have Sr concentrations >750 ppm, avg. LaN/YbN = 23.1, and initial 87Sr/86Sr ratios that range from 0.70617 to 0.70686. This study proposes that the parental QIC magma (initial 87Sr/86Sr = 0.706) can be derived bypartial melting of an amphibolitic source reservoir at lower crustal conditions. Geochemical data (Rb, Sr, Ba and LaN/YbN) and initial 87Sr/86Sr ratios preclude linkages between the two suites by fractional crystallization or assimilation and fractional crystallization (AFC) processes. The suite I rocks are interpreted to be the result of magma mixing between the QIC parental magma and a mantle derived magma. The samples do not lie along a single mixing line due to continued evolution through fractional crystallization/AFC processes subsequent to magma mixing. The suite II rocks may be generated by AFC. Initial 87Sr/86Sr ratio data suggests that similar processes to those that affected the QIC may also have operated during the generation of other portions of the Great Tonalite Sill of southeast Alaska.en_US
dc.publisherVirginia Techen_US
dc.relation.haspartJTHESIS2.pdfen_US
dc.rightsI hereby grant to Virginia Tech or its agents the right to archive and to make available my thesis or dissertation in whole or in part in the University Libraries in all forms of media, now or hereafter known. I retain all proprietary rights, such as patent rights. I also retain the right to use in future works (such as articles or books) all or part of this thesis or dissertation.en_US
dc.subjectQuottoon plutonen_US
dc.subjectquartz dioriteen_US
dc.subjecttonaliteen_US
dc.subjectmagmaen_US
dc.subjectBritish Columbiaen_US
dc.subjectAlaskaen_US
dc.subjectpetrographyen_US
dc.subjectmajor elementsen_US
dc.subjecttrace elementsen_US
dc.subjectrare earth elementsen_US
dc.subjectgeochemistryen_US
dc.subjectSr isotopesen_US
dc.subjectgeochemical modelingen_US
dc.subjectGreat Tonalite Sillen_US
dc.titlePetrologic Significance of Multiple Magmas in the Quottoon Igneous Complex, NW British Columbia and SE Alaskaen_US
dc.typeThesisen_US
dc.contributor.departmentGeological Sciencesen_US
dc.description.degreeMaster of Scienceen_US
thesis.degree.nameMaster of Scienceen_US
thesis.degree.levelmastersen_US
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen_US
thesis.degree.disciplineGeological Sciencesen_US
dc.contributor.committeechairSinha, A. Krishnaen_US
dc.contributor.committeememberSinha, A. Krishnaen_US
dc.contributor.committeememberCrawford, Maria L.en_US
dc.contributor.committeememberBeard, James S.en_US
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-52598-142754/en_US
dc.date.sdate1998-05-18en_US
dc.date.rdate1999-06-26
dc.date.adate1998-06-26en_US


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