Nd isotopic characterization of metamorphic rocks in the Coast Mountains, Alaskan and Canadian cordillera: ancient crust bounded by juvenile terranes

S. D. Samson, P. J. Patchett, W. C. McClelland, G. E. Gehrels

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Abstract

Nd isotopic data are reported for 52 samples from the crustal region between the Alexander-Wrangellia terrane and the Stikine terrane of the Alaskan and Canadian Cordillera. This region is composed of the Gravina belt, a Jurassic-Cretaceous assemblage of volcanic and clastic sedimentary rocks, the Taku terrane, and four assemblages of metamorphic rocks. The isotopic signatures indicate that a substantial component of each metamorphic assemblage was derived from Precambrian continental crust. Possible tectonic scenarios that can explain the present geometry of the YTT with respect to the Alexander-Wrangellia and Stikine terranes include: 1) the YTT is the upturned stratigraphic basement of the Stikine terrane, 2) part of the YTT was structurally emplaced beside the Stikine terrane in a transpressive tectonic regime, 3) the Stikine terrane and other inboard terranes are huge sheets that were thrust over the margin of the YTT before the final accretion of the Alexander-Wrangellia terrane. -from Authors

Original languageEnglish (US)
Pages (from-to)770-780
Number of pages11
JournalTectonics
Volume10
Issue number4
StatePublished - 1991

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ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics

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