Timing of arc construction and metamorphism in the Slate Creek Complex, Northern Sierra Nevada, California

Timothy Jay Fagan, H. W. Day, B. R. Hacker

Research output: Contribution to journalArticle

13 Citations (Scopus)

Abstract

Late Paleozoic to early Mesozoic rocks in the Sierra Nevada and Klamath Mountains, western United States, preserve a record of lateral growth of continental crust by incorporation of ophiolites, volcanic arcs, and associated sedimentary rocks. Deciphering the timing of arc construction and metamorphism is critical for elucidating tectonic and thermal evolution during this type of crustal growth, but is difficult in complex accretionary terranes. In this study, we address the timing of arc construction and regional metamorphism in the Slate Creek Complex, a volcano-plutonic terrane in the central part of the northern Sierra Nevada. New 40Ar-39Ar ages from relict volcanic hornblende demonstrate that the youngest volcanic unit in the Slate Creek Complex is ca. 170 Ma, at least 30 m.y. younger than previous estimates of ca. 200 Ma for metaplutonic rocks in the lower part of the complex. Consequently, the Slate Creek Complex is polygenetic, with two distinct episodes of arc magmatism. The distribution of mineral assemblages and textures indicates that greenschist and epidote-amphibolite facies metamorphism is younger than 170 Ma and is associated with cross-cutting plutons that yield cooling ages of 150 Ma and younger. Amphiboles from foliated rocks in the Slate Creek Complex yield plateau ages of 156.1 ± 0.6 and 152.0 ± 0.7 Ma that date cooling subsequent to or dynamic recrystallization during the metamorphic event. Age and lithologic similarities suggest that the lower parts of the Slate Creek Complex correlate with plutons (ca. 200 Ma) and the volcanic cover sequence of the Rattlesnake Creek terrane in the Klamath Mountains. The uppermost volcanic unit correlates with the ca. 170 Ma Western Hayfork terrane that structurally overlies the Rattlesnake Creek terrane. Metamorphism in the Slate Creek Complex correlates broadly with a similar late metamorphic event in the Klamath Mountains.

Original languageEnglish
Pages (from-to)1105-1118
Number of pages14
JournalBulletin of the Geological Society of America
Volume113
Issue number8
DOIs
Publication statusPublished - 2001 Aug
Externally publishedYes

Fingerprint

slate
metamorphism
terrane
pluton
mountain
rock
cooling
creek
greenschist
thermal evolution
regional metamorphism
epidote
amphibolite facies
tectonic evolution
hornblende
amphibole
continental crust
island arc
magmatism
sedimentary rock

Keywords

  • Amphibole
  • Ar/Ar
  • Continental accretion
  • Island arcs
  • Jurassic
  • Sierra Nevada

ASJC Scopus subject areas

  • Earth and Planetary Sciences (miscellaneous)

Cite this

Timing of arc construction and metamorphism in the Slate Creek Complex, Northern Sierra Nevada, California. / Fagan, Timothy Jay; Day, H. W.; Hacker, B. R.

In: Bulletin of the Geological Society of America, Vol. 113, No. 8, 08.2001, p. 1105-1118.

Research output: Contribution to journalArticle

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