Thesis
Precambrian basement rocks of the Clearwater metamorphic complex: a new piercing point along the western margin of Laurentia
Washington State University
Master of Science (MS), Washington State University
2012
Handle:
https://hdl.handle.net/2376/104733
Abstract
Interest in the geochronology of Eocene metamorphic core complexes in the northern Cordillera of the United States has increased in the past decade. The driving forces behind many of these studies have been the discovery of previously unrecognized Precambrian basement rocks and the increased precision and accessibility of geochronology instrumentation. Until this study, only a handful of dates have been published for metaigneous and metasedimentary rocks of the Clearwater complex. Geological mapping coupled with laser-ablation zircon geochronology have identified new exposures of Neoarchean (2676 Ma) and Paleoproterozoic (1853 Ma) metaigneous rocks. Isotopically, metaigneous rocks have positive initial epsilon Nd values suggesting the involvement of juvenile mantle material and recycled Archean lithosphere. Metasedimentary rocks in the study area fall into two categories: sediments with U-Pb detrital zircon ages > 1.73 Ga and sediments with U-Pb detrital zircon ages < 1.73 Ga; both categories exhibit slightly negative to slightly positive initial Nd epsilon values. Metasedimentary rocks with U-Pb ages >1731 Ma indicate a time of deposition after the emplacement of Paleoproterozoic intrusions and probably prior to the formation of the ~1.45 Ga Belt-Purcell Supergroup. Metasedimentary rocks with U-Pb ages < 1731 Ma indicate a time of deposition after the emplacement of Paleoproterozoic intrusions and after initiation of the Belt-Purcell sedimentation. Although the exact nature of the contact relationships between the metaigneous basement rocks and the surrounding metasedimentary rocks is not know in detail, the rocks in the eastern Clearwater complex provide new isotopic, geochronologic, and lithologic information about the poorly understood time period between creation of Precambrian basement and the formation of the Mesoproterozoic Belt-Purcell Supergroup. In total, these new data provide a new piercing point along the western margin of Laurentia that can be used in the reconstruction of Rodinia.
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Details
- Title
- Precambrian basement rocks of the Clearwater metamorphic complex
- Creators
- Andrew Christian Jansen
- 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, Wash. :
- Identifiers
- 99900525006601842
- Language
- English
- Resource Type
- Thesis