Structure, petrology, and tectonic history of the Leech River complex northwest of Victoria, Vancouver Island
The Leech River complex 45 km northwest of Victoria consists of metamorphosed pelitic rocks, sandstone, and minor volcanic rocks, chert, and conglomerate of probable Late Jurassic to Cretaceous age. The assemblage experienced two similar deformational events during which regional shortening induced macroscopic east-plunging folds and related coaxial, mesoscopic linear structures, parasitic folds, and axial-plane cleavages. Fragmentation along the developing cleavages disrupted layering and eventually led to transposition during both events. Regional, progressive, low-pressure greenschist- to amphibolite-facies (andalusite–staurolite–biotite) metamorphism began during the first deformation and extended into the waning stages of the second. Intrusion of composite felsic sills was synchronous with deformation and metamorphism, which concluded about 39–41 Ma, according to K–Ar data. The Leech River fault, which forms the southern boundary of the complex, is a zone of two to four subparallel faults. All are re...