Date of Award:
5-2002
Document Type:
Thesis
Degree Name:
Master of Science (MS)
Department:
Geosciences
Department name when degree awarded
Geology
Committee Chair(s)
John W. Shervais
Committee
John W. Shervais
Abstract
The Cuesta Ridge ophiolite is one of the best-preserved remnants of mid-Jurassic ophiolite in California. Geologic mapping and petrologic studies show that it comprises (1) harzburgite mantle tectonite, (2) dunite-rich mantle transition zone (MTZ), (3) wehrlite and pyroxenite, (4) isotropic gabbro, (5) sheeted dike/sill complex, (6) volcanic rocks (7) late-stage dikes and flows, and (8) tuffaceous radiolarian chert.
The sheeted dike/sill complex is dominated by quartz diorite, with significant modal quartz and hornblende. The volcanic section is dominated by arc tholeiite and boninitic lavas. Boninites, with high MgO, Cr, and Ni comprise 40% of the volcanic rocks. Latestage dikes and lava flows below the overlying chert, have a MORB-like affinity.
These data suggest formation in a supra-subduction zone setting with three stages of arc-related magmatism before late-stage MORB magmatism. I infer formation above the east-dipping proto-Franciscan subduction zone and suggest that ophiolite formation was terminated by a ridge subduction/collision event.
Checksum
a25aa8a0425cfc74da001cc2662a80e3
Recommended Citation
Snow, Cameron A., "Geology of the Cuesta Ridge Ophiolite Remnant near San Luis Obispo, California: Evidence for the Tectonic Setting and Origin of the Coast Range Ophiolite" (2002). All Graduate Theses and Dissertations, Spring 1920 to Summer 2023. 6737.
https://digitalcommons.usu.edu/etd/6737
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