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Master of Science (MS)
Brown, Edwin H.
Burmester, Russell F.
Babcock, R. Scott (Randall Scott)
A complex record of orogenesis is preserved in part of a large country rock septum within the southeast Coast Plutonic Complex (CPC) near the Kwoiek Creek area of British Columbia. The study area includes part of the large 90-84 Ma Scuzzy Pluton. Country rock is the Settler Schist near the pluton, and the slightly metamorphosed Permo-Jurassic Bridge River assemblage, a subduction-accretionary complex, and the hemipelagic Cayoosh assemblage. Earliest deformation produced isoclinal folds and an axial planar foliation. Subsequent folds are southwest vergent, and produced a spaced cleavage. High angle reverse faulting along the Bralorne-Kwoiek Creek Fault followed. The area then underwent greenschist to sillimanite facies metamorphism and associated deformation produced by intrusion of the Scuzzy Pluton.
Pebble shapes in metaconglomerates in the host rocks are dominantly oblate and show no relationship to distance from the pluton, reflecting strains prior to intrusion of the pluton. The flattened pebble fabric is tightly to isoclinally folded by deformation related to intrusion of the pluton.
The metamorphic zones and associated foliation parallel the pluton, locally crossing regional structural trends. Rocks in the aureole were deformed throughout intrusion. Early synkinematic andalusite in the Scuzzy aureole is pseudomorphed by late postkinematic sillimanite and kyanite. Pressures of 3.4 kbar, obtained from roof pendants, indicate the parts of the pluton were at shallow crustal levels early during intrusion. Pressures determined for rocks in the pluton and the aureole that reflect later conditions during metamorphism are between 4.4 to 5.9 kbar, indicating a pressure increase of 1 to 2.5 kbar during intrusion. Shear sense indicators show that rocks farther than 0.5 km from the pluton moved downward, while those near the contact underwent solid-state flow upward.
This information indicates that high grade metamorphism and associated deformation coincide with intrusion of the Scuzzy pluton, and that crustal loading occurred during its emplacement. The cause of crustal loading is most simply explained by the accumulation of magma, plutonic or volcanic, at higher levels in the crust. Thrust loading during plutonism is not ruled out, but is less likely given the absence of solid-state fabrics in the pluton.
Coast Plutonic Complex, Orogenesis, Scuzzy pluton
Western Washington University
Subject – LCSH
Geology, Structural--British Columbia--Kwoiek Creek Region; Metamorphism (Geology)--British Columbia--Kwoiek Creek Region
Kwoiek Creek Region (B.C.)
Copying of this document in whole or in part is allowable only for scholarly purposes. It is understood, however, that any copying or publication of this thesis for commercial purposes, or for financial gain, shall not be allowed without the author's written permission.
Alvarez, Kristine M. (Kristine Marie), "Structure and Metamorphism of the Kwoiek Creek Area, British Columbia" (1996). WWU Graduate School Collection. 829.