Geology and U-Pb geochronology of Archean basement and Proterozoic cover in the Priest River Complex, northwestern United States, and their implications for Cordilleran structure and Precambrian continent reconstructions

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doi: 10.1139/e97-083
Authors:Doughty, P. T.; Price, R. A.; Parrish, R. R.
Author Affiliations:Primary:
Exxon Production Research Company, Houston, TX, United States
Queen's University, Canada
University of Leicester, United Kingdom
Volume Title:Canadian Journal of Earth Sciences Revue Canadienne des Sciences de la Terre
Source:Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre, 35(1), p.39-54. Publisher: National Research Council of Canada, Ottawa, ON, Canada. ISSN: 0008-4077
Publication Date:1998
Note:In English with French summary. 64 refs.; illus., incl. 2 tables, geol. sketch maps
Summary:Precambrian basement rocks exposed within tectonic windows in the North American Cordillera help to define the Precambrian crustal structure of western North America and possible reconstructions of the Late Proterozoic supercontinent Rodinia. New geologic mapping and U-Pb dating in the infrastructure of the Priest River metamorphic complex, northern Idaho, documents the first Archean basement (2651±20 Ma) north of the Snake River Plain in the North American Cordillera. The Archean rocks are exposed in the core of an antiform and mantled by a metaquartzite that may represent the nonconformity between basement and the overlying Hauser Lake gneiss, which is correlated with the Prichard Formation of the Belt Supergroup. A structurally higher sheet of augen gneiss interleaved with the Hauser Lake gneiss yields a U-Pb zircon crystallization age somewhat greater than 1577 Ma. The slivers of augen gneiss were tectonically interleaved with the surrounding Hauser Lake gneiss near the base of the Spokane dome mylonite zone, which arches across this part of the Priest River complex. We conclude that the Spokane dome mylonite zone lies above the Archean basement-cover contact and that it was, in part, equivalent to the basal decollement of the Rocky Mountain fold and thrust belt. New U-Pb dates on metamorphic monazite and xenotime reveal peak metamorphism at ca. 72 Ma. compatible with movement along the Spokane dome mylonite zone at that time. The Archean basement could be interpreted as the western extension of the Hearne province, or a new Archean basement terrane separated from the Hearne province by an Early Proterozoic suture. The unique assemblage of 2.65 Ga basement, ∼1.58 Ga felsic intrusive rocks, and the Middle Proterozoic Belt Supergroup can be used as a piercing point for the identification of the conjugate margin to Laurentia. Our new dating supports previous correlations of Australia's Gawler craton (2.55-2.65 Ga) and its 1590 Ma plutons with the Priest River complex basement gneisses. The Priest River complex basement may be a piece of eastern Australia stranded during rifting of the supercontinent Rodina in the Late Proterozoic.
Subjects:Absolute age; Augen gneiss; Basement; Continental drift; Dates; Gneisses; Metaigneous rocks; Metamorphic rocks; Metamorphism; Nesosilicates; Orthosilicates; Plate tectonics; Precambrian; Reconstruction; Sedimentary cover; Silicates; U/Pb; Zircon; Zircon group; Bonner County Idaho; Idaho; North America; North American Cordillera; United States; Northern Idaho; Priest River Complex
Coordinates:N481000 N481000 W1164500 W1164500
Abstract Numbers:98M/2258
Record ID:1998040883
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute.
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