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Mid-Paleozoic initiation of the northern Cordilleran marginal backarc basin: Geologic, geochemical, and neodymium isotope evidence from the oldest mafic magmatic rocks in the Yukon-Tanana terrane, Finlayson Lake district, southeast Yukon, Canada

2004; Geological Society of America; Volume: 116; Issue: 9 Linguagem: Inglês

10.1130/b25162.1

1943-2674

Stephen J. Piercey, Donald C. Murphy, James K. Mortensen, Robert A. Creaser,

earthquake and tectonic studies

Research Article| September 01, 2004 Mid-Paleozoic initiation of the northern Cordilleran marginal backarc basin: Geologic, geochemical, and neodymium isotope evidence from the oldest mafic magmatic rocks in the Yukon-Tanana terrane, Finlayson Lake district, southeast Yukon, Canada Stephen J. Piercey; Stephen J. Piercey 1Mineral Deposit Research Unit, Department of Earth and Ocean Sciences, University of British Columbia, 6339 Stores Road, Vancouver, British Columbia V6T 1Z4, Canada Search for other works by this author on: GSW Google Scholar Donald C. Murphy; Donald C. Murphy 2Yukon Geological Survey, P.O. Box 2703 (K-10), Whitehorse, Yukon Y1A 2C6, Canada Search for other works by this author on: GSW Google Scholar James K. Mortensen; James K. Mortensen 3Department of Earth and Ocean Sciences, University of British Columbia, 6339 Stores Road, Vancouver, British Columbia V6T 1Z4, Canada Search for other works by this author on: GSW Google Scholar Robert A. Creaser Robert A. Creaser 4Department of Earth and Atmospheric Sciences, University of Alberta, 126 ESB, Edmonton, Alberta T6G 1E3, Canada Search for other works by this author on: GSW Google Scholar Author and Article Information Stephen J. Piercey 1Mineral Deposit Research Unit, Department of Earth and Ocean Sciences, University of British Columbia, 6339 Stores Road, Vancouver, British Columbia V6T 1Z4, Canada Donald C. Murphy 2Yukon Geological Survey, P.O. Box 2703 (K-10), Whitehorse, Yukon Y1A 2C6, Canada James K. Mortensen 3Department of Earth and Ocean Sciences, University of British Columbia, 6339 Stores Road, Vancouver, British Columbia V6T 1Z4, Canada Robert A. Creaser 4Department of Earth and Atmospheric Sciences, University of Alberta, 126 ESB, Edmonton, Alberta T6G 1E3, Canada Publisher: Geological Society of America Received: 04 Apr 2002 Revision Received: 31 Oct 2003 Accepted: 19 Nov 2003 First Online: 02 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 Geological Society of America GSA Bulletin (2004) 116 (9-10): 1087–1106. https://doi.org/10.1130/B25162.1 Article history Received: 04 Apr 2002 Revision Received: 31 Oct 2003 Accepted: 19 Nov 2003 First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Stephen J. Piercey, Donald C. Murphy, James K. Mortensen, Robert A. Creaser; Mid-Paleozoic initiation of the northern Cordilleran marginal backarc basin: Geologic, geochemical, and neodymium isotope evidence from the oldest mafic magmatic rocks in the Yukon-Tanana terrane, Finlayson Lake district, southeast Yukon, Canada. GSA Bulletin 2004;; 116 (9-10): 1087–1106. doi: https://doi.org/10.1130/B25162.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search Abstract The Fire Lake formation of the Yukon-Tanana terrane in the Finlayson Lake region, Yukon, Canada, consists primarily of Late Devonian (ca. 365–360 Ma) mafic metavolcanic rocks and smaller volumes of mafic and ultramafic subvolcanic metamorphosed intrusions. In this paper, field, geochemical, and Nd isotope attributes of these rocks are presented in an attempt to understand their tectonic setting, the magmatic processes involved in their formation, and their roles in Cordil-leran crustal growth. The mafic rocks of the Fire Lake formation exhibit a wide diversity of geochemical signatures and are classified into seven chemically defined suites: (1) back-arc-basin basalt, (2) enriched mid-oceanic-ridge basalt (E-MORB), (3) oceanic-island basalt (OIB), (4) Th-rich OIB, (5) boninite, (6) island-arc tholeiite, and (7) light rare earth element (LREE)–enriched island-arc tholeiite. The diversity of geochemical signatures is interpreted to represent variable mixtures of asthenospheric (MORB-type) mantle, subarc mantle wedge, and lithospheric (OIB-type) mantle with or without elemental contributions from the subducted slab and/or continental crust. These suites of rocks are also associated with fine-grained basinal sedimentary facies, variations in metavolcanic and metasedimentary unit thickness, extensional synvolcanic faults, and apparent extensional-fault–controlled emplacement of mafic intrusive rocks and hydrothermal volcanic-hosted massive sulfide mineralization. The suites also exhibit a broad spatial distribution; those with "arc" signatures (Nb/Thmn < 1; mn—normalized to primitive mantle values) are located primarily in the western parts of the formation, and suites with "nonarc" signatures (Nb/Thmn ≥ 1) are located primarily within the eastern parts of the formation. Collectively, these geologic and geochemical attributes are interpreted to stem from the transition from arc magmatism to the initiation of an extensional backarc basinal environment associated with an east-dipping subduction zone.The initiation of backarc-basin magmatism recorded in the Fire Lake formation was part of a much larger Late Devonian backarc basinal system forming along the western edge of the margin of North America. The Fire Lake formation is interpreted to represent (1) the commencement of Yukon-Tanana arc rifting and separation from the North American cratonic margin, and (2) the initiation of a marginal (backarc) basin (now the Slide Mountain terrane) inboard of the Yukon-Tanana arc system. This tectonic evolution likely occurred either as a result of slab rollback toward the west within the convergent margin responsible for Yukon-Tanana arc activity or as a result of the propagation of the Slide Mountain backarc-basin spreading ridges into the Yukon-Tanana arc system. This Yukon-Tanana arc rifting episode was also broadly coincident with rifting and hydrothermal activity within rocks of the North American craton.The geochemical and isotopic signatures of magmatic rocks in the Fire Lake formation have some features similar to intraoceanic arc rocks (e.g., boninites, island-arc tholei-ites), and many have juvenile Nd isotope signatures (i.e., ϵNd(t) > 0; most have ϵ Nd(t) > +5), suggesting that the pericratonic terranes of the northern Cordillera have a significant juvenile component. If this is the case throughout the Yukon-Tanana terrane, then the pericratonic terranes may have contributed much more juvenile material to Cordil-leran crustal growth in the Phanerozoic than has previously been considered. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.