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Architecture of pericratonic Yukon-Tanana terrane in the northern Cordillera
Author(s) -
J J Ryan,
A Zagorevski,
N R Cleven,
A. J. Parsons,
Nancy Joyce
Publication year - 2021
Language(s) - English
Resource type - Reports
DOI - 10.4095/326062
Subject(s) - terrane , geology , north american plate , cretaceous , devonian , shear zone , geochemistry , fibrous joint , metamorphic rock , paleontology , geomorphology , tectonics , plate tectonics , medicine , anatomy
West-central Yukon and eastern Alaska are characterized by widespread metamorphic rocks that form part of the allochthonous, composite Yukon-Tanana terrane and parautochthonous North American margin. Structural windows through the Yukon-Tanana terrane exposeparautochthonous North American margin in that broad region, particularly as mid-Cretaceous extensional core complexes. Both the Yukon-Tanana terrane and parautochthonous North American margin share the same Late Devonian history, making their discrimination difficult; however, distinct post-LateDevonian magmatic and metamorphic histories assist in discriminating Yukon-Tanana terrane from parautochthonous North American margin rocks. The suture between Yukon-Tanana terrane and parautochthonous North American margin is obscured by many episodes of high-strain deformation. Their main boundingstructure is probably a Jurassic to Cretaceous thrust, which has been locally reactivated as a mid-Cretaceous extensional shear zone. Crustal-scale structures within composite Yukon-Tanana terrane (e.g. the Yukon River shear zone) are commonly marked by discontinuous mafic-ultramafic complexes. Someof these complexes represent orogenic peridotites that were structurally exhumed into the Yukon-Tanana terrane in the Middle Permian.