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Geochemistry of ophiolitic rocks associated with the western part of the Elk outlier of the western Klamath terrane, southwestern Oregon

By
Mario J. Giaramita
Mario J. Giaramita
Department of Physics and Geology, California State University, Stanislaus, 801 W. Monte Vista Avenue, Turlock, California 95382, USA
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Gregory D. Harper
Gregory D. Harper
Department of Earth and Space Sciences, State University of New York Albany, 1400 Washington Avenue, Albany, New York 12222, USA
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Published:
January 01, 2006

A newly discovered dike complex and serpentinite-matrix mélange may represent basement for the Upper Jurassic Galice Formation in the Elk outlier of the western Klamath terrane, which lies far to the west of the Klamath Mountains province. The fault-bounded dike complex consists of virtually 100% parallel dikes with scarce diorite screens and amphibole-rich hydrothermal metamorphic assemblages, all consistent with it being a sheeted dike complex of an ophiolite. Magmatic affinities of the dikes are transitional island-arc tholeiite (IAT) to mid-ocean ridge basalt (MORB) and boninitic, similar to the Josephine ophiolite that underlies the Galice Formation elsewhere. The mélange includes blocks of mafic volcanic (many pillowed) and hypabyssal rocks, igneous breccia, amphibolite, pyroxenite, peridotite, and metasandstone in a sheared serpentinite matrix. Volcanic rocks and amphibolites have MORB magmatic affinities, and some of the pillow lavas are unusual highly fractionated Fe-Ti basalts. Hypabyssal blocks have MORB, within-plate, and calc-alkaline affinities. The magmatic affinities of the mélange blocks are distinct from the dike complex, and thus the mélange and dike complex are unrelated petrogenetically. The mélange may belong to the underlying Pickett Peak terrane of the Franciscan Complex, or it may be part of the western Klamath terrane and correlative to Lower Mesozoic ophiolitic rocks found elsewhere in “rift-edge facies” of the Josephine ophiolite. The Elk outlier is far to the north of the part of the western Klamath terrane that contains the Josephine ophiolite. Thus, the presence of a remnant of the Josephine ophiolite in the Elk outlier would be consistent with Cretaceous dextral strike-slip displacement proposed by previous workers or with the Josephine extending farther north than previously recognized.

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GSA Special Papers

Geological Studies in the Klamath Mountains Province, California and Oregon: A volume in honor of William P. Irwin

Arthur W. Snoke
Arthur W. Snoke
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Calvin G. Barnes
Calvin G. Barnes
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Geological Society of America
Volume
410
ISBN print:
9780813724102
Publication date:
January 01, 2006

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