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Structural, metamorphic, and geochronologic constraints on the origin of the Clearwater core complex, northern Idaho

P. Ted Doughty, Kevin R. Chamberlain, David A. Foster and Grant S. Sha
Structural, metamorphic, and geochronologic constraints on the origin of the Clearwater core complex, northern Idaho (in Whence the mountains? Inquiries into the evolution of orogenic systems; a volume in honor of Raymond A. Price, James W. Sears (editor), Tekla A. Harms (editor) and Carol A. Evenchick (editor))
Special Paper - Geological Society of America (2007) 433: 211-241

Abstract

New structural, metamorphic, and geochronologic data from the Clearwater complex, north-central Idaho, define the origin and exhumation history of the complex. The complex is divisible into an external zone bound by normal faults and strike-slip faults of the Lewis and Clark Line, and an internal zone of Paleoproterozoic basement exposed in two shear zone-bounded culminations. U-Pb sensitive high-resolution ion microprobe (SHRIMP) dating of metamorphic zircon overgrowths from the external zone yield zircon growth at ca. 70-72 Ma and 80-82 Ma, during peak metamorphism and before tectonic exhumation of the external zone. U-Pb SHRIMP dating of metamorphic zircon rims from the internal zone record growth at ca. 64 and between 59 and 55 Ma. The older ages record pre-extension metamorphism. The younger rim ages were derived from fractured zircons in the Jug Rock shear zone, and they document the beginning of exhumation of the internal zone along deep-seated shear zones that transported the basement rocks to the west. The (super 40) Ar/ (super 39) Ar ages record quenching of the external zone starting ca. 54 Ma and the internal zone between 53 and 47 Ma by movement along the bounding faults and internal shear zones. After ca. 47 Ma, extension was accommodated via a west-dipping detachment that was active until after ca. 41 Ma. The Clearwater complex is interpreted as an Eocene metamorphic core complex that formed in an extensional relay zone between faults of the Lewis and Clark Line.


ISSN: 0072-1077
EISSN: 2331-219X
Coden: GSAPAZ
Serial Title: Special Paper - Geological Society of America
Serial Volume: 433
Title: Structural, metamorphic, and geochronologic constraints on the origin of the Clearwater core complex, northern Idaho
Title: Whence the mountains? Inquiries into the evolution of orogenic systems; a volume in honor of Raymond A. Price
Author(s): Doughty, P. TedChamberlain, Kevin R.Foster, David A.Sha, Grant S.
Author(s): Sears, James W.editor
Author(s): Harms, Tekla A.editor
Author(s): Evenchick, Carol A.editor
Affiliation: Eastern Washington University, Department of Geology, Cheney, WA, United States
Affiliation: University of Montana, Department of Geosciences, Missoula, MT, United States
Pages: 211-241
Published: 2007
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 72
Accession Number: 2008-088183
Categories: Structural geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 plates, 4 tables, geol. sketch maps
N46°15'00" - N47°45'00", W116°15'00" - W115°00'00"
Secondary Affiliation: Amherst College, USA, United StatesNatural Resources Canada, CAN, CanadaUniversity of Wyoming, USA, United StatesUniversity of Florida, USA, United StatesHalliburton Energy Services, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute.
Update Code: 200827
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