Thesis
Age and origin of the Archean and Paleoproterozoic basement rocks from the Priest River and Clearwater complexes, Northern Idaho
Washington State University
Master of Science (MS), Washington State University
2015
Handle:
https://hdl.handle.net/2376/103167
Abstract
Basement rocks are important for constraining the early history of the Earth. In this study, samples were collected from the basement terrane south of Coeur d'Alene, Idaho in order to determine the relationships of this crust to the Priest River complex to the north and the Clearwater complex to the southeast. Eleven metaigneous and three metasedimentary samples were studied for zircon U-Pb geochronology and Lu-Hf isotope composition. The metaigneous samples yield an Archean 207Pb/206Pb age of 2.65 Ga and Paleoproterozoic ages ranging from 1.87 Ga to 1.86 Ga. Together with previous dated basement rocks in the Clearwater complex, all samples collectively define a bimodal age distribution at ~2.65 Ga and ~1.86 Ga. The metasedimentary samples were dated to constrain the depositional age. The youngest detrital zircon in the Red Hog Ridge quartzite gives a 207Pb/206Pb age of 1.73 Ga. The age distribution of these quartzites is similar to the Neihart Quartzite in Montana, indicating a Laurentian source. A paragneiss sample has the youngest detrital zircon age of 1.46 Ga. The age pattern in this sample matches the signature of the Hauser Lake gneiss, indicating a non-Laurentian source. Zircon Hf analyses of samples from both complexes yield tight positive [epsilon]Hf(t) values (~ 0 - +4) for the Archean samples (2.66 Ga - 2.65 Ga) and a wide range of [epsilon]Hf(t) for the Paleoproterozoic samples (1.87 Ga - 1.84 Ga) from ~ -8 to +8. These zircon Hf results indicate that the Archean samples formed at 2.65 Ga were derived from a relatively homogenous mantle source and the Paleoproterozoic orthogneisses were formed at ~1.86 Ga from the mixing of various amount of depleted mantle input and evolved continental crust. It is likely that these basement rocks are from the same piece of basement province. In comparison with other basement terranes in northwestern Laurentia, the crystalline basement in the Priest River and Clearwater complexes appear to be distinct from the Wyoming province and the Medicine Hat block, although the latter is poorly known. If so, the Priest River and Clearwater complexes may represent a distinct Archean-Paleoproterozoic crustal block--the Clearwater block
Metrics
27 File views/ downloads
64 Record Views
Details
- Title
- Age and origin of the Archean and Paleoproterozoic basement rocks from the Priest River and Clearwater complexes, Northern Idaho
- Creators
- Da Wang
- 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
- 99900525150701842
- Language
- English
- Resource Type
- Thesis