Refining Ages of Granitic Rocks at the Intersection of the Sevier Orogeny and Priest River Core Complex in the Spokane Area
Faculty Mentor
Chad Pritchard, PhD
Presentation Type
Poster
Start Date
5-8-2024 9:00 AM
End Date
5-8-2024 10:45 AM
Location
PUB NCR
Primary Discipline of Presentation
Geosciences
Abstract
Granitic outcrops in the Spokane area have commonly been mapped as Cretaceous to Tertiary. Recent U/Pb ages using LA-ICP-MS of separated zircon grains are presented from numerous granitic outcrops to help refine geochronology of the region. Ages measured from granitic rocks in the area reflect three time periods, Cretaceous (Sevier Orogeny), Paleocene and Eocene (Priest River core complex). The Cretaceous granite is west of the Priest River core complex. Paleocene granitic rocks show strong deformation textures that may be associated with the early ages of core complex formation. Small slivers of highly deformed orthogneiss and paragneiss west of the Priest River core complex could have been translated by normal faults from the upper part of the core complex, or are themselves small core complexes. Eocene granite along the eastern margin of the core complex in the Spokane area is likely directly related to partial melting associated with the core complex. Economic deposits, such as Silver Hill, seem to be located at margins of Eocene intrusions and these defendable ages will be used to further understand the geologic history of the Spokane area.
Recommended Citation
Smith, Marilyn L.; Pritchard, Chad PhD; and Gaschnig, Richard PhD, "Refining Ages of Granitic Rocks at the Intersection of the Sevier Orogeny and Priest River Core Complex in the Spokane Area" (2024). 2024 Symposium. 43.
https://dc.ewu.edu/srcw_2024/ps_2024/p1_2024/43
Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International License.
Refining Ages of Granitic Rocks at the Intersection of the Sevier Orogeny and Priest River Core Complex in the Spokane Area
PUB NCR
Granitic outcrops in the Spokane area have commonly been mapped as Cretaceous to Tertiary. Recent U/Pb ages using LA-ICP-MS of separated zircon grains are presented from numerous granitic outcrops to help refine geochronology of the region. Ages measured from granitic rocks in the area reflect three time periods, Cretaceous (Sevier Orogeny), Paleocene and Eocene (Priest River core complex). The Cretaceous granite is west of the Priest River core complex. Paleocene granitic rocks show strong deformation textures that may be associated with the early ages of core complex formation. Small slivers of highly deformed orthogneiss and paragneiss west of the Priest River core complex could have been translated by normal faults from the upper part of the core complex, or are themselves small core complexes. Eocene granite along the eastern margin of the core complex in the Spokane area is likely directly related to partial melting associated with the core complex. Economic deposits, such as Silver Hill, seem to be located at margins of Eocene intrusions and these defendable ages will be used to further understand the geologic history of the Spokane area.
