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Detrital zircon U-Pb geochronology and Hf isotope geochemistry of Paleozoic and Triassic passive margin strata of western North America

George Gehrels and Mark Pecha
Detrital zircon U-Pb geochronology and Hf isotope geochemistry of Paleozoic and Triassic passive margin strata of western North America
Geosphere (Boulder, CO) (December 2013) 10 (1): 49-65

Abstract

U-Pb geochronologic and Hf isotopic analyses have been conducted on detrital zircons extracted from 36 samples of Neoproterozoic through Triassic passive margin strata from western North America. The data serve as an improved reference for comparison with inboard strata that accumulated on the North American craton and outboard strata belonging to potentially displaced Cordilleran terranes. As expected, this reference documents significant variations in ages and Hf isotope compositions both north-south and also through time. The data also provide insights into the provenance of Cordilleran passive margin strata. During Neoproterozoic, Cambrian, and Early-Middle Devonian time, most grains were shed from relatively local basement rocks and from Mesoproterozoic clastic strata containing 1.2-1.0 Ga grains that originated in the Grenville orogen. This pattern was interrupted during Ordovician time, when much of the Cordilleran margin was blanketed by detritus shed from the northern Canadian Shield. Beginning in Late Devonian time, and continuing through late Paleozoic and Triassic time, most regions were dominated by locally derived detritus (largely recycled from underlying strata), but also received 0.7-0.4 Ga grains that were shed from the Franklinian, Caledonian, Appalachian, and Ouachita-Marathon orogens. This pattern is complicated in southern transects as a result of mid-Paleozoic emplacement of off-shelf assemblages onto the continental margin (e.g., Antler orogeny) and construction of Permo-Triassic magmatic arcs along the margin. Our data also provide a robust record of the crustal evolution of western North America, with significant production of juvenile crust during late Archean (3.0-2.5 Ga) and Paleoproterozoic (1.78-1.6 Ga) time and phases of mainly crustal reworking at 2.0-1.78, 1.5-1.3, 1.2-1.0, and 0.6-0.2 Ga. This history is somewhat different from that of other continents, with western Laurentia comprising a greater overall proportion of juvenile crust, punctuated by greater degrees of crustal reworking between 2.2 and 1.78 Ga and 0.3-0.2 Ga.


EISSN: 1553-040X
Serial Title: Geosphere (Boulder, CO)
Serial Volume: 10
Serial Issue: 1
Title: Detrital zircon U-Pb geochronology and Hf isotope geochemistry of Paleozoic and Triassic passive margin strata of western North America
Affiliation: University of Arizona, Department of Geosciences, Tucson, AZ, United States
Pages: 49-65
Published: 20131219
Text Language: English
Publisher: Geological Society of America, Boulder, CO, United States
References: 87
Accession Number: 2014-004478
Categories: Isotope geochemistryGeochronologyStratigraphy
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. geol. sketch map
N42°00'00" - N84°00'00", W141°00'00" - W52°00'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data from GeoScienceWorld, Alexandria, VA, United States. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201404
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