Tectonothermal Evolution of the Southern Omineca Belt, Southeastern British Columbia

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atmire.migration.oldid4595
dc.contributor.advisorPattison, David
dc.contributor.authorWebster, Ewan
dc.contributor.committeememberGuest, Bernard
dc.contributor.committeememberSimony, Philip
dc.contributor.committeememberCuthbertson, Jennifer
dc.contributor.committeememberLarson, Kyle
dc.contributor.committeememberBirss, Viola
dc.date.accessioned2016-07-13T19:50:30Z
dc.date.available2016-07-13T19:50:30Z
dc.date.issued2016
dc.date.submitted2016en
dc.description.abstractThis study documents the geological structure, metamorphism, U-Pb geochronology, 40Ar/39Ar thermochronology and tectonic evolution of the Omineca belt of southeastern British Columbia. In this area, three tectonic domains with different tectono-metamorphic histories spatially overlap. In the southwest of the study area, Early Jurassic deformation and greenschist facies metamorphism (D1M1) is crosscut by Middle Jurassic intrusions of the Nelson suite (174-161Ma) that were emplaced at approximately 9-15km depth. A subdomain of Jurassic 40Ar/39Ar cooling ages is centered over these intrusions, suggesting rapid cooling and exhumation to upper crustal levels, where they have remained. The Jurassic structures are progressively overprinted northwards by Early Cretaceous deformation and Barrovian metamorphism (D2M2) in a domain that is abruptly terminated to the west by the Eocene Midge Creek fault (MCF) and to the east by the Purcell Trench faults (PTF). Peak sillimanite zone metamorphism occurred at 6-7kbar and 650-700ºC. The D2M2 domain is the southerly continuation of a 144-134Ma domain of regional deformation and metamorphism to the north of the study area. Metamorphic isograds associated with M2 metamorphism are transected by intrusions of the mid-Cretaceous Bayonne suite (118-90Ma). Microstructures and cross-cutting relations reveal that D2 deformation outlasted M2 metamorphism, was ongoing as late as 118Ma, but ceased by 111Ma. South of the Barrovian metamorphic belt and in the hangingwall of the PTF and MCF, 40Ar/39Ar ages record a regional, mid-Cretaceous thermal event. The Early Cretaceous D2M2 makes a southerly transition into a domain of Late Cretaceous (ca. 80-70Ma) regional Barrovian metamorphism and deformation (D3M3) bounded by the PTF and Blazed Creek-Next Creek fault. 40Ar/39Ar cooling ages are indistinguishable from monazite U-Pb ages of peak metamorphism (ca. 70Ma), implying rapid exhumation of these rocks during the Late Cretaceous. This narrow domain of cooling ages extends across the cryptic interface between the Early and Late Cretaceous Barrovian metamorphic belts, suggesting exhumation as one continuous block. 53-45Ma 40Ar/39Ar cooling ages in the immediate footwall of the PTF suggest extension did not commence until ~53Ma. Therefore, exhumation occurs via a two-stage process: 1) rapid decompression in the Late Cretaceous (70-60Ma); 2) exhumation in the footwall of Eocene extensional structures (53-45Ma).en_US
dc.identifier.citationWebster, E. (2016). Tectonothermal Evolution of the Southern Omineca Belt, Southeastern British Columbia (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/27991en_US
dc.identifier.doihttp://dx.doi.org/10.11575/PRISM/27991
dc.identifier.urihttp://hdl.handle.net/11023/3129
dc.language.isoeng
dc.publisher.facultyGraduate Studies
dc.publisher.institutionUniversity of Calgaryen
dc.publisher.placeCalgaryen
dc.rightsUniversity of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission.
dc.subjectGeochemistry
dc.subjectGeology
dc.subjectMineralogy
dc.subject.classificationmetamorphicen_US
dc.subject.classificationPetrologyen_US
dc.subject.classificationominecaen_US
dc.subject.classificationGeochronologyen_US
dc.subject.classificationTectonicsen_US
dc.titleTectonothermal Evolution of the Southern Omineca Belt, Southeastern British Columbia
dc.typedoctoral thesis
thesis.degree.disciplineGeology and Geophysics
thesis.degree.grantorUniversity of Calgary
thesis.degree.nameDoctor of Philosophy (PhD)
ucalgary.item.requestcopytrue
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