Chilliwack composite terrane in northwest washington: Neoproterozoic-silurian passive margin basement, ordovician-silurian arc inception

E. H. Brown, George E Gehrels, V. A. Valencia

Research output: Contribution to journalArticle

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Abstract

The Chilliwack composite terrane in northwest Washington is part of an assemblage of mid-Paleozoic arc terranes extending from California to Alaska. Some terranes bear evidence of exotic origin, whereas others apparently formed proximal to western Laurentia, posing a complex problem in unraveling the Paleozoic accretionary history of the Cordillera. In our proposed broader definition, the Chilliwack composite terrane includes the volcanic and sedimentary East Sound and Chilliwack groups, and the plutonic and metamorphic Turtleback and Yellow Aster complexes. New zircon ages indicate that the plutonic and volcanic rocks are mutually related as parts of the same arc complex and that its inception was as old as Late Ordovician to Silurian, older than most other parts of the mid-Paleozoic terrane assemblage. Base-ment to the arc complex is a passive margin assemblage of metamorphosed quartzose sandstone and calc-silicate rock of the Yellow Aster Complex, bracketed in age by ca. 1000 Ma detrital zircons and 418 Ma intrusive rocks. This association of paragneiss basement and overlying and (or) intruding arc resembles that of older parts of the extensive Yukon-Tanana terrane in the northern Cordillera. Detrital zircon ages support a western Laurentian pericratonic origin for the paragneiss basement and the overlying arc. However, an early to mid-Paleozoic connection of this assemblage to the exotic outboard Alexander terrane is also indicated, based on (1) Mesoproterozoic and early Paleozoic detrital zircons in Devonian sedi-mentary rocks of the arc, and also in certain other pericratonic Devonian terranes and strata of the miogeocline; (2) Late Ordovician - Silurian igneous ages; and (3) an earliest Devonian or older metamorphic age of the basement paragneiss.

Original languageEnglish (US)
Pages (from-to)1347-1366
Number of pages20
JournalCanadian Journal of Earth Sciences
Volume47
Issue number10
DOIs
StatePublished - Oct 2010

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passive margin
Silurian
terrane
Ordovician
Paleozoic
zircon
cordillera
calc silicate rock
Laurentia
plutonic rock
rock
volcanic rock
sandstone
history

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)

Cite this

Chilliwack composite terrane in northwest washington : Neoproterozoic-silurian passive margin basement, ordovician-silurian arc inception. / Brown, E. H.; Gehrels, George E; Valencia, V. A.

In: Canadian Journal of Earth Sciences, Vol. 47, No. 10, 10.2010, p. 1347-1366.

Research output: Contribution to journalArticle

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