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Age, chemistry, and correlations of Neoproterozoic-Devonian igneous rocks of the Arctic Alaska-Chukotka Terrane; an overview with new U-Pb ages

Jeffrey M. Amato, John N. Aleinikoff, Vyacheslav V. Akinin, William C. McClelland and Jaime Toro
Age, chemistry, and correlations of Neoproterozoic-Devonian igneous rocks of the Arctic Alaska-Chukotka Terrane; an overview with new U-Pb ages (in Reconstruction of a late Proterozoic to Devonian continental margin sequence, northern Alaska; its paleogeographic significance, and contained base-metal sulfide deposits, Julie A. Dumoulin and Alison B. Till)
Special Paper - Geological Society of America (July 2014) 506: 29-57

Abstract

The Arctic Alaska-Chukotka terrane is a microcontinent with an origin exotic to Laurentia. We used a sensitive high-resolution ion microprobe (SHRIMP) to date nine samples of Neoproterozoic rock and five samples of Devonian rock from the Brooks Range and Seward Peninsula of Alaska and from the Chukotka Peninsula of northeastern Russia. Felsic magmatism occurred at 968 Ma and 742 Ma in the Brooks Range and at 865 Ma and 670-666 Ma on Seward Peninsula. Felsic igneous rocks in Chukotka were dated at 656 Ma and 574 Ma. Devonian igneous rocks are found throughout the Arctic Alaska-Chukotka terrane, and we dated samples with ages of 391 Ma, 390 Ma, 385 Ma, 371 Ma, and 363 Ma. The felsic character of the Neoproterozoic rocks suggests formation at least in part through crustal melting. The age of the crustal source rocks that melted to form the Neoproterozoic rocks is inferred to be Mesoproterozoic based on Nd model ages ranging from 1.6 to 1.4 Ga. Rocks of this age range have been reported from the basement of Baltica but are rare in Laurentia. The 565 Ma orthogneisses on Seward Peninsula have ca. 1.1 Ga Nd model ages. Devonian igneous rocks have a wide range of model ages ranging from 1.6 to 0.8 Ga. The tectonic setting of the 968 Ma, 865 Ma, and 742 Ma rocks is unknown. The ca. 670 Ma magmatism on Seward Peninsula is interpreted to have occurred in an arc setting based on geochemistry and similarities in their ages to the Avalonian-Cadomian arc system peripheral to Gondwana. Latest Neoproterozoic magmatism is inferred to have occurred in a rift setting based on composition and the Paleozoic passive margin sequence that was deposited across the Arctic Alaska-Chukokta terrane. Devonian magmatism likely occurred in an arc and/or backarc rift setting. Significant uncertainties remain concerning the age of the Arctic Alaska-Chukotka terrane basement, particularly the age of the host rocks for Neoproterozoic intrusions.


ISSN: 0072-1077
EISSN: 2331-219X
Coden: GSAPAZ
Serial Title: Special Paper - Geological Society of America
Serial Volume: 506
Title: Age, chemistry, and correlations of Neoproterozoic-Devonian igneous rocks of the Arctic Alaska-Chukotka Terrane; an overview with new U-Pb ages
Title: Reconstruction of a late Proterozoic to Devonian continental margin sequence, northern Alaska; its paleogeographic significance, and contained base-metal sulfide deposits
Author(s): Amato, Jeffrey M.Aleinikoff, John N.Akinin, Vyacheslav V.McClelland, William C.Toro, Jaime
Author(s): Dumoulin, Julie A.
Author(s): Till, Alison B.
Affiliation: New Mexico State University, Department of Geological Sciences, Las Cruces, NM, United States
Affiliation: U. S. Geological Survey, Anchorage, AK, United States
Pages: 29-57
Published: 201407
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
ISBN: 978-0-8137-2506-2
References: 81
Accession Number: 2014-076398
Categories: GeochronologyIgneous and metamorphic petrology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 5 tables, geol. sketch maps
N66°00'00" - N69°40'00", W165°00'00" - W141°00'00"
N64°00'00" - N72°00'00", W170°00'00" - E153°00'00"
N37°00'00" - N83°00'00", W170°00'00" - E28°00'00"
N64°19'60" - N66°34'00", W168°04'60" - W161°19'60"
Secondary Affiliation: U. S. Geological Survey, USA, United StatesRussian Academy of Sciences, North East Scientific Research Institute, RUS, Russian FederationUniversity of Iowa, USA, United StatesWest Virginia University, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2017, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 201440
Program Name: USGSOPNon-USGS publications with USGS authors
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