Structure, petrology, and tectonic history of the Leech River Complex northwest of Victoria, Vancouver Island

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doi: 10.1139/e82-161
Authors:Fairchild, Lee H.; Cowan, Darrel S.
Author Affiliations:Primary:
Univ. Wash., Dep. Geol. Sci., Seattle, WA, United States
Volume Title:Canadian Journal of Earth Sciences Revue Canadienne des Sciences de la Terre
Source:Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre, 19(9), p.1817-1835. Publisher: National Research Council of Canada, Ottawa, ON, Canada. ISSN: 0008-4077
Publication Date:1982
Note:In English with French summary. 30 refs.; illus. incl. 1 table, geol. sketch maps
Summary:This complex consists of metamorphosed pelitic rocks, sandstone, minor volcanic rocks, cherts and conglomerate of probable Late Jurassic - Cretaceous age. The assemblage experienced two similar deformations during which regional shortening induced macroscopic E-plunging folds and related coaxial, mesoscopic linear structures, parasitic folds, and axial-plane cleavages. Fragmentation along the cleavages disrupted layering and led to transposition during both events. Low-P metamorphism began during the first deformation and extended into the waning stages of the second. Intrusion of felsic sills was synchronous with deformation and metamorphism, which concluded approx 30-41 m.y. B.P. The Leech River fault, which forms the S boundary of the complex, is a zone of two to four subparallel faults that appear to dip steeply. This structure is interpreted as a left-lateral strike-slip fault, active exclusively after 39-41 m.y. The Leech River complex is interpreted as allochthonous with respect to the bulk of Vancouver Island, derived from a cryptic terrain to the W emplaced against Vancouver Island by left-lateral slip on the San Juan fault after 39-41. m.y. ago. Major-element analyses of three metavolcanic rocks are presented. [P.Br.]
Subjects:Axial-plane structures; Cleavage; Complexes; Cretaceous; Faults; Folds; Interference patterns; Interpretation; Jurassic; Lineation; Mesozoic; Metamorphic rocks; Metamorphism; Mineral assemblages; P-T conditions; Petrology; Plate tectonics; Prograde metamorphism; Regional metamorphism; Strike-slip faults; Structural analysis; Structural geology; Tectonics; Upper Jurassic; British Columbia; Canada; Vancouver Island; Western Canada; Leech River Complex
Coordinates:N482000 N484000 W1234500 W1240000
Abstract Numbers:83M/1999
Record ID:1983002667
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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