Thesis
Geochronology of the metamorphic rocks of the western Clearwater complex: a study using Lu-Hf garnet and U-Pb zircon geochronology
Washington State University
Master of Science (MS), Washington State University
2019
Handle:
https://hdl.handle.net/2376/102578
Abstract
Recent work in the Clearwater metamorphic complex and associated Priest River complex has revealed a wealth of Precambrian basement exposures and a complex Precambrian metamorphic record preserved in the rocks of north-central Idaho (Sha et al., 2004; Zirakparvar, 2007; Jansen, 2012; Nesheim et al., 2012; Wang, 2015; Vervoort et al., 2016). The rocks exposed in the western part of the Clearwater metamorphic complex have until recently remained relatively unresearched. In this study, U-Pb zircon analyses of orthogneisses identified new Archean (2667 Ma) and Paleoproterozoic (1878 Ma) crystallization ages from the western part of the Clearwater complex. These ages are associated with Precambrian crust building magmatism recognized from the recently proposed Clearwater block (Vervoort et al., 2016). Detailed mapping and U-Pb zircon analyses also reveal new exposures of possible pre-Belt metasedimentary rocks. Detrital zircon samples analyzed yield U-Pb ages entirely >1720 Ma and lack "western source" zircons from the so-called "North American magmatic gap" ca. 1610-1490 Ma (Ross and Villeneuve, 2003). Possible sediment sources for abundant 1.8-1.7 Ga detrital zircons found in the proposed pre-Belt samples are discussed, including the Yavapai and Mazatzal provinces of southwest Laurentia, the "Big White Arc" of Link et al. (2016), the Big Sky orogeny southwest of the Great Falls tectonic zone, and the Gawler craton of Australia. Lutetium-hafnium garnet isochron ages for metamorphic rocks from both the western and interior zones of the Clearwater complex ca. 1409, 1349, 1325, and 1187 Ma are reported as well. Garnet growth ca. 1.4 Ga is interpreted to be related to the emplacement of the Moyie sills. Garnet growth ca 1.3 Ga may be related to the East Kootenay orogeny. The garnet-bearing sample which yielded an age of 1187 Ma is interpreted to represent a mixing of garnet growth associated with the older East Kootenay orogeny and the assembly of the supercontinent Rodinia ca. 1.1-1.0 Ga. The sum of ages reported in this study further resolves the complex Precambrian tectonic record preserved along the deformed western margin of Laurentia.
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Details
- Title
- Geochronology of the metamorphic rocks of the western Clearwater complex
- Creators
- Clay Daniel McDonie
- Contributors
- Jeffrey D. Vervoort (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Environment, School of the (CAHNRS)
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525175601842
- Language
- English
- Resource Type
- Thesis