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Title: Protolith relations of the Gravina belt and Yukon-Tanana terrane in central southeastern Alaska

Abstract

Metamorphic rocks west of the Coast Mountains batholith in central southeastern Alaska are divided into the Gravina belt, Taku terrane, and newly defined Ruth assemblage. The Ruth assemblage comprises metapelite, quartzose metaclastic strata, quartzite, marble, felsic metatuff, mafic metavolcanic rocks, and orthogneiss. Depositional and emplacement ages of 367 {plus minus} 10 Ma and 345 {plus minus} 13 Ma inferred from discordant U/Pb zircon analyses on felsic metatuff and granodioritic orthogneiss, respectively, require that at least portions of the Ruth assemblage be Late Devonian and early Mississippian in age. The assemblage is similar in age and protolith to, and thus correlated with, the Yukon-Tanana terrane. The Gravina belt is characterized by upper Jurassic and lower Cretaceous mafic volcanic rocks and tuffaceous turbiditic clastic strata that unconformably overlie the Alexander terrane. Metamorphic rocks that structurally underlie the Taku terrane and Rugh assemblage are included in this assemblage. Trace element geochemistry and the abundance of pyroclastic flows associated with tuffaceous turbidites suggest that the Gravina belt evolved in an intra-arc basinal setting. In central southeastern Alaska, the mid-Cretaceous structure that currently separates the Ruth assemblage (Yukon-Tanana correlative) from the Gravina belt marks the fundamental boundary between the Alexander-Wrangellia terrane and inboard Yukon-Tanana andmore » Stikine terranes.« less

Authors:
 [1]; ;  [2];  [3]
  1. Univ. of California, Santa Barbara (United States)
  2. Univ. of Arizona, Tucson (United States)
  3. Syracuse Univ., NY (United States)
Publication Date:
OSTI Identifier:
7003962
Resource Type:
Journal Article
Journal Name:
Journal of Geology; (United States)
Additional Journal Information:
Journal Volume: 100:1; Journal ID: ISSN 0022-1376
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; ALASKA; GEOLOGIC FORMATIONS; VOLCANIC REGIONS; METAMORPHIC ROCKS; ISOTOPE DATING; PETROGENESIS; VOLCANIC ROCKS; CARBONIFEROUS PERIOD; CORRELATIONS; CRETACEOUS PERIOD; DEVONIAN PERIOD; GEOCHEMISTRY; JURASSIC PERIOD; LEAD ISOTOPES; URANIUM ISOTOPES; ZIRCON; ACTINIDE ISOTOPES; AGE ESTIMATION; CHEMISTRY; DEVELOPED COUNTRIES; GEOLOGIC AGES; IGNEOUS ROCKS; ISOTOPES; MESOZOIC ERA; MINERALS; NORTH AMERICA; PALEOZOIC ERA; ROCKS; SILICATE MINERALS; USA; 580000* - Geosciences

Citation Formats

McClelland, W C, Gehrels, G E, Patchett, P J, and Samson, S D. Protolith relations of the Gravina belt and Yukon-Tanana terrane in central southeastern Alaska. United States: N. p., 1992. Web. doi:10.1086/629574.
McClelland, W C, Gehrels, G E, Patchett, P J, & Samson, S D. Protolith relations of the Gravina belt and Yukon-Tanana terrane in central southeastern Alaska. United States. doi:10.1086/629574.
McClelland, W C, Gehrels, G E, Patchett, P J, and Samson, S D. Wed . "Protolith relations of the Gravina belt and Yukon-Tanana terrane in central southeastern Alaska". United States. doi:10.1086/629574.
@article{osti_7003962,
title = {Protolith relations of the Gravina belt and Yukon-Tanana terrane in central southeastern Alaska},
author = {McClelland, W C and Gehrels, G E and Patchett, P J and Samson, S D},
abstractNote = {Metamorphic rocks west of the Coast Mountains batholith in central southeastern Alaska are divided into the Gravina belt, Taku terrane, and newly defined Ruth assemblage. The Ruth assemblage comprises metapelite, quartzose metaclastic strata, quartzite, marble, felsic metatuff, mafic metavolcanic rocks, and orthogneiss. Depositional and emplacement ages of 367 {plus minus} 10 Ma and 345 {plus minus} 13 Ma inferred from discordant U/Pb zircon analyses on felsic metatuff and granodioritic orthogneiss, respectively, require that at least portions of the Ruth assemblage be Late Devonian and early Mississippian in age. The assemblage is similar in age and protolith to, and thus correlated with, the Yukon-Tanana terrane. The Gravina belt is characterized by upper Jurassic and lower Cretaceous mafic volcanic rocks and tuffaceous turbiditic clastic strata that unconformably overlie the Alexander terrane. Metamorphic rocks that structurally underlie the Taku terrane and Rugh assemblage are included in this assemblage. Trace element geochemistry and the abundance of pyroclastic flows associated with tuffaceous turbidites suggest that the Gravina belt evolved in an intra-arc basinal setting. In central southeastern Alaska, the mid-Cretaceous structure that currently separates the Ruth assemblage (Yukon-Tanana correlative) from the Gravina belt marks the fundamental boundary between the Alexander-Wrangellia terrane and inboard Yukon-Tanana and Stikine terranes.},
doi = {10.1086/629574},
journal = {Journal of Geology; (United States)},
issn = {0022-1376},
number = ,
volume = 100:1,
place = {United States},
year = {1992},
month = {1}
}