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The Origin of Serpentinites Associated with the Shuksan Metamorphic Suite Near Gee Point, Washington
Date Permissions Signed
5-20-2018
Date of Award
Winter 1978
Document Type
Masters Thesis
Degree Name
Master of Science (MS)
Department
Geology
First Advisor
Brown, Edwin H.
Second Advisor
Pevear, David R.
Third Advisor
Babcock, R. Scott (Randall Scott)
Abstract
Metavolcanic and metasedimentary rocks of the Shuksan Metamorphic Suite near Gee Point have been contact metamorphosed by high-temperature emplacement of ultramafic rock. This intrusion occurred at great depth (>25 km) and caused contact temperatures of about 500°C, resulting in epidote-amphibolite facies metamorphism. Minerals of the contact metamorphism are overprinted by mineral assemblages of the regional Shuksan blueschist facies metamorphism. The K/Ar age of the epidote-amphibolites is Jurassic (145-160 m.y.), and thus the age of Shuksan metamorphism is probably younger than Middle Jurassic.
Ultramafic rocks found near Gee Point have been metamorphosed to serpentinites during Shuksan metamorphism and should be considered part of the Shuksan Metamorphic Suite.
Shuksan blueschist facies metamorphism and the Gee Point epidote-amphibolite facies metamorphism probably occurred within a subduction zone. A tectonic model is proposed in which high-temperature ultramafic rock fills fractures and faults in a subducted plate, causing local contact metamorphism.
Comparison of metamorphic relations at Gee Point with rocks of the Franciscan Complex suggests that Franciscan eclogites may also result from contact metamorphism caused by ultramafic intrusions.
Type
Text
Keywords
Shuksan blueschist facies
DOI
https://doi.org/10.25710/0zk1-ra10
Publisher
Western Washington University
OCLC Number
1056712088
Subject – LCSH
Ultrabasic rocks; Geology--Washington (State)--Skagit County; Serpentinite--Washington (State)--Skagit County; Crystalline rocks
Geographic Coverage
Skagit County (Wash.)
Format
application/pdf
Genre/Form
masters theses
Language
English
Rights
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.
Recommended Citation
Wilson, Daniel L., "The Origin of Serpentinites Associated with the Shuksan Metamorphic Suite Near Gee Point, Washington" (1978). WWU Graduate School Collection. 779.
https://cedar.wwu.edu/wwuet/779
Geologic Map of the Northern Part of the Oso Quadrangle