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Rocky Mountain (53rd) and South-Central (35th) Sections, GSA, Joint Annual Meeting (April 29–May 2, 2001)

Paper No. 0
Presentation Time: 1:00 PM-5:00 PM

SYNEMPLACEMENT DEFORMATION OF THE MIDDLE CRETACEOUS CAPTAIN COVE PLUTON: TILTING OR LARGE-SCALE TERRANE TRANSLATION?


BURGETT, Darren1, ANDRONICOS, Christopher L.2, BULLOSS, Nick1 and ROHRBAUGH, Robert T.1, (1)Department of Geological Sciences, Univ of Texas at El Paso, El Paso, TX 79968, (2)Geological Sciences, The Univ of Texas at El Paso, El Paso, TX 79968, darren@geo.utep.edu

The Captain Cove pluton is a middle Cretaceous calc-alkaline batholith emplaced in the Coast Plutonic Complex of western British Columbia. Foliations within the Captain Cove pluton are steeply dipping and vary from magmatic to solid-state. Deformation is most intense along the western side of the pluton where it intrudes the Kitkatla shear zone. Kinematic indicators, developed within both country rock gneisses and the pluton, include C/S fabrics, porphyroclasts and shear bands that indicate sinistral displacements during pluton emplacement. Upright, northwest trending folds developed near the margins of the pluton suggest sub-horizontal shortening during pluton emplacement. The pluton has a tadpole shape, with a series of east-northeast trending thrust faults developed near the head of the tadpole. A transpressive strain field is indicated by the presence of strike-slip shear-zones, thrust shear zones, and folds that record horizontal shortening. We conclude, based on these observations, that the Captain Cove pluton was intruded during sinistral transpressive shearing in mid-Cretaceous time. Butler et al. (1989) suggested that the Captain Cove pluton was tilted about a sub-horizontal NW trending axis, based on Paleomagnetic data. Alternatively, paleomagnetic data may indicate large northward translation with a vertical axis rotation of the Captain Cove pluton after its emplacement. We are currently acquiring pressure estimates using hornblende barometry. We will use hornblende barometry and structural relationships to estimate paleo-horizontal in order to test the tilting hypothesis. We will present our results at the meeting. This data will place important new constraints on Cretaceous tectonics along the western margin of North America.

Butler, R.F., Geherls, G.E., McClelland, W.C., May, S. R., and Klepacki, D. (1989), Discordant paleomagnetic poles from the Canadian Coast Plutonic Complex: Regional tilt rather than large-scale terrane displacement. Geology, 17, 691-694.

Session No. 7--Booth# 40

T1. Undergraduate Research Session (Posters)
Monday, 30 April 2001: 1:00 PM-5:00 PM
Geological Society of America Abstracts with Programs. Vol. 33, No. 5, April 2001, p.12
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