Abstract
Age and tectonic setting of eclogites in the St. Cyr area, Yukon-Tanana Terrane, Canadian Cordillera
Abstracts with programs - Geological Society of America, Vol.44(7), p.494
Geological Society of America, 2012 annual meeting
11/2012
Abstract
Variably retrogressed to well-preserved eclogites are found as meter- to tens of meter-scale lenses within quartzofeldspathic rocks in the St. Cyr area, Yukon of the Canadian Cordillera. The quartzofeldspathic schists consist of both sedimentary and igneous protoliths that display a continuous, steep to moderately dipping, northwest-striking foliation. Metasedimentary rocks include garnet- and kyanite-bearing quartzites, garnet-mica schists and feldspar-quartz-mica schists. Felsic meta-igneous rocks include garnet-bearing metatonalites and metatrondhjemites. The eclogites and their host rocks form a coherent slab approximately 30 km long by 6 km thick. Serpentinized ultramafic rocks and associated gabbros and amphibolites are interleaved tectonic slices within the eclogite-bearing quartzofeldspathic crust. We use SHRIMP-RG and LA-ICP-MS U-Pb zircon geochronology and trace element geochemistry to characterize the age and tectonic affinity of protoliths, detrital provenance and timing of high-pressure (HP) metamorphism in the St. Cyr area. Eclogite yields protolith ages of 379 + or - 4 and 369 + or - 3 Ma. Eclogite boudins have N-MORB and island arc tholeiite protoliths. Provenance ages of metasedimentary rocks range from ca. 1.8 Ga to 370 Ma, similar in age to the oldest rocks in the Yukon-Tanana Terrane. Felsic intrusive rocks give magmatic ages between 346 + or - 4 and 333 + or - 3 Ma, coeval with the Klinkit magmatic succession of the Yukon-Tanana Terrane. Late Permian HP metamorphism of the eclogites and their host quartzofeldspathic schists occurred between 274 + or - 4 and 266 + or - 3 Ma. Zircons from both eclogites and quartzofeldspathic schists give trace element signatures characteristic of eclogite-facies metamorphism, with depleted heavy rare earth element patterns and no Eu anomaly. The association of eclogites with HP arc-derived sedimentary and felsic intrusives indicates a primary association with felsic arcs of the Yukon-Tanana Terrane rather than intra-oceanic rocks of the Slide Mountain Terrane. Slices of ultramafic and lower grade metabasic rocks now spatially associated with the eclogite-bearing HP unit may represent imbrication of Yukon-Tanana and Slide Mountain Terrane material during exhumation of the HP crust.
Details
- Title: Subtitle
- Age and tectonic setting of eclogites in the St. Cyr area, Yukon-Tanana Terrane, Canadian Cordillera
- Creators
- Meredith Petrie - University of Iowa, Department of Geoscience Iowa City, IA USA United StatesJane A GilottiWilliam C McClellandCees R van Staal
- Resource Type
- Abstract
- Publication Details
- Abstracts with programs - Geological Society of America, Vol.44(7), p.494
- Conference
- Geological Society of America, 2012 annual meeting
- Publisher
- Geological Society of America (GSA)
- ISSN
- 0016-7592
- Alternative title
- Geological Society of America, 2012 annual meeting
- Language
- English
- Date published
- 11/2012
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984240891502771
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