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

T. J. Fagan*, H. W. Day, B. R. Hacker

*この研究の対応する著者

研究成果: Article査読

18 被引用数 (Scopus)

抄録

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.

本文言語English
ページ(範囲)1105-1118
ページ数14
ジャーナルBulletin of the Geological Society of America
113
8
DOI
出版ステータスPublished - 2001 8
外部発表はい

ASJC Scopus subject areas

  • 地質学

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