Metamorphic history of Alaska

Dusel-Bacon, Cynthia

doi:10.3133/ofr91556

Cited by 6 publications

(6 citation statements)

References 124 publications

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“…The Yakutat Group is regionally metamorphosed to zeolite to prehnite-pumpellyite facies and locally metamorphosed to greenschist facies (Dusel-Bacon, 1994; this study). Building upon mapping by Plakfer and Miller (1957), Richter et al (2005) subdivided the Yakutat Group into fl ysch and mélange assemblages.…”

Section: Tectonic Settingmentioning

confidence: 80%

Structural relationships in the eastern syntaxis of the St. Elias orogen, Alaska

Chapman¹,

Pavlis²,

Bruhn³

et al. 2012

Geosphere

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Section: Tectonic Settingmentioning

confidence: 80%

Structural relationships in the eastern syntaxis of the St. Elias orogen, Alaska

Chapman¹,

Pavlis²,

Bruhn³

et al. 2012

Geosphere

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“…2) Mortensen, 1990). Devonian-Mississippian augen granitoids are also present in eastern Alaska (Dusel-Bacon andAleinikoff, 1985, 1996) and southeastern Yukon (Piercey et al, 2003a) (Fig. 1).…”

Section: Augen Granitoid Suitesmentioning

confidence: 95%

Mid- to late Paleozoic K-feldspar augen granitoids of the Yukon-Tanana terrane, Yukon, Canada: Implications for crustal growth and tectonic evolution of the northern Cordillera

Ruks¹,

Piercey²,

Ryan³

et al. 2006

Geological Society of America Bulletin

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Potassic feldspar-bearing augen granitoids are a fundamental component of the architecture of the Yukon-Tanana terrane and the ancient Pacifi c margin of the northern Cordillera. These augen granitoids form a belt that extends from Alaska to southeast Yukon Territory, vary in age, and provide probes of the crustal evolution and tectonic history of the Yukon-Tanana terrane and ancient Pacifi c margin of North America in the Paleozoic. We present results of an integrated fi eld mapping, geochemical, Sm-Nd tracer isotopic, and U-Pb zircon geochronologic study of the augen granitoids in the Stewart River area in an attempt to understand their role in the crustal evolution and tectonic history of the Yukon-Tanana terrane and ancient Pacifi c margin of North America.Augen granitoids of the Stewart River area are of three distinct ages: Late Devonian, early Mississippian, and Permian. U-Pb zircon geochronology of these augen granitoids has yielded ages of 362.1 ± 2.7 Ma (Stewart River augen granite), 347.5 ± 0.7 Ma (Mount Burnham augen granite), and 264.8 ± 3.7 Ma (Wounded Moose augen granite). All of the augen granitoids, regardless of age, have negative ε Ndt values (−2.0 to −15.3) and Proterozoic-Archean depleted-mantle model ages (T DM = 1.37-2.56 Ga). These geochemical and isotopic attributes, coupled with the presence of inherited zircon with Precambrian ages, suggest that these granitoids are the product of crustal melting and crust-mantle mixing during three different cycles of arc magmatism in the Paleozoic. Furthermore, these granitoids represent net crustal recycling along the ancient Pacifi c margin of North America in the Paleozoic. Importantly, however, there are minor secular variations in crustal recycling, and the younger Permian augen granitoids exhibit higher ε Ndt , Nb/Ta, V/Yb, and Sc/Yb, consistent with a greater juvenile component in their genesis. This juvenile component is probably due to assimilation of underplated mafi c material derived from older early Mississippian Yukon-Tanana terrane arc magmatism and/or a greater mantle component due to enhanced infi ltration of underplated mafi c material into augen granitoid magma chambers through rheologically weak crust associated with Permian subduction.The older Late Devonian and early Mississippian augen granitoid suites represent two pulses of Yukon-Tanana terrane arc magmatic activity that developed in response to east-dipping subduction along the western edge of the North America craton in the mid-Paleozoic. This east-dipping Yukon-Tanana terrane arc system continued to evolve throughout the Mississippian to Early Permian and was coincident with the development of the Slide Mountain backarc basin that formed between the Yukon-Tanana terrane arc system and the North American craton; this east-dipping arc-backarc system continued until ca. 275 Ma. After ca. 275 Ma, the east-dipping arc and backarc magmatism ceased and was replaced by ca. 270-269 Ma high-pressure metamorphism and the establishment of a new subduction zone that formed in response t...

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“…1. The northern section consists of continental affinity metamorphic and granitoid rocks of the Yukon composite terrane that are partially overlain by sedimentary strata of the Neogene Tanana basin (Figures 2 and 3a) [ Dusel‐Bacon , 1994; Foster et al , 1994; Ridgway et al , 2007; Dusel‐Bacon and Williams , 2009]. The Northern Foothills and the Kantishna Hills regions represent the southernmost exposures of Yukon composite terrane rocks in our study area (Figures 1 and 3a).…”

Section: Background and Previous Studiesmentioning

confidence: 99%

Crustal structure across the central Alaska Range: Anatomy of a Mesozoic collisional zone

Brennan

Gilbert

Ridgway

2011

Geochem Geophys Geosyst

102

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[1] A first-order process in the growth of continents is the collision and accretion of terranes against continental margins. Collision leads to the formation of a suture zone between the accreted terrane and the former continental margin. New insights on the suturing process are observed from two receiver function transects across the Mesozoic Alaska Range suture zone. Three distinct crustal sections are identified from observations of crustal thickness, intracrustal discontinuities, and Vp/Vs: a northern section with ∼27 km thick crust of felsic to intermediate composition, a central section that is ∼37 km thick that exhibits intracrustal discontinuities and has felsic to intermediate composition, and a southern section that is ∼30 km thick and has a more mafic composition. We interpret these sections to correspond with the former continental margin (Yukon composite terrane), the suture zone proper, and the allochthonous oceanic terrane (Wrangellia composite terrane). The boundary between the Yukon composite terrane and the suture zone appears to be a subhorizontal discontinuity that accommodated underthrusting of crust from the suture zone beneath the former continental margin. The boundary between the suture zone and the Wrangellia composite terrane, in contrast, appears to be a relatively discrete, vertical boundary. The observed variability in the crust across the Alaska Range suture zone is likely controlled by the differing compositions of the terranes involved, which influences how each section responds to precollisional, syncollisional, and postcollisional deformation.

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Metamorphic history of Alaska

Cited by 6 publications

References 124 publications

Structural relationships in the eastern syntaxis of the St. Elias orogen, Alaska

Structural relationships in the eastern syntaxis of the St. Elias orogen, Alaska

Mid- to late Paleozoic K-feldspar augen granitoids of the Yukon-Tanana terrane, Yukon, Canada: Implications for crustal growth and tectonic evolution of the northern Cordillera

Crustal structure across the central Alaska Range: Anatomy of a Mesozoic collisional zone

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