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Early Proterozoic magmatism in Yukon, Canada: constraints on the evolution of northwestern Laurentia

Citation

Thorkelson, D and Mortenson, JK and Creaser, RA and Davidson, GJ and Abbott, JG, Early Proterozoic magmatism in Yukon, Canada: constraints on the evolution of northwestern Laurentia, Canadian Journal of Earth Sciences, 38, (10) pp. 1479-1494. ISSN 0008-4077 (2001) [Refereed Article]

DOI: doi:10.1139/cjes-38-10-1479

Abstract

Northwestern Laurentia, after cratonization at about 1.85 Ga, underwent a series of tectonic and magmatic events during the Proterozoic that were followed by separation of Laurentia from another landmass, probably Australia. The oldest magmatic event produced the Bonnet Plume River Intrusions (BPRI), which intruded the Wernecke Supergroup as short dikes and small stocks. The BPRI are hydrothermally altered tholeiitic diorites, gabbros, and subordinate anorthositic and syenitic rocks, with trace element signatures consistent with a rift origin. Depleted mantle model ages range from 2.29 to 2.57 Ga and εNd values range from +0.7 to -1.7. An increasing crustal component is apparent in rocks with more evolved compositions. Four U-Pb zircon ages (1705.9 ± 0.7, 1709.4 ± 1.4, 1711.1 ± 5.1, and 1713.6 ± 12.7 Ma) indicate a Paleoproterozoic age for the BPRI. These dates constrain the age of the Wernecke Supergroup to ≥ ca. 1710 Ma, making it the oldest supracrustal succession in western Laurentia, e.g., >240 Ma older than the Belt Supergroup of southeastern British Columbia and the northwestern United States. The Wernecke Supergroup was deposited in the first rift basin to open along the western margin of Laurentia, but was later inverted by the pre-1.6 Ga Racklan Orogeny, an event possibly influenced by transmission of compression from the Yavapai and Mazatzal orogenies in southern Laurentia. The Neoproterozoic southwestern United States - east Antarctica (SWEAT) reconstruction, which places Australia next to northwestern Laurentia, is supported by linkages between Paleoproterozoic and Mesoproterozoic geological features in northwestern Canada and Australia.

Item Details

Item Type:Refereed Article
Research Division:Earth Sciences
Research Group:Geology
Research Field:Igneous and Metamorphic Petrology
Objective Division:Expanding Knowledge
Objective Group:Expanding Knowledge
Objective Field:Expanding Knowledge in the Earth Sciences
Author:Davidson, GJ (Dr Garry Davidson)
ID Code:23264
Year Published:2001
Web of Science® Times Cited:53
Deposited By:Centre for Ore Deposit Research - CODES CoE
Deposited On:2001-08-01
Last Modified:2011-09-27
Downloads:0

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