Structural, metamorphic, and geochronologic constraints on the origin of the Condrey Mountain Schist, north central Klamath Mountains, northern California
The Condrey Mountain Schist (CMS) occupies a window through Late Triassic amphibolite facies melange in the north central Klamath Mountains in northern California and southwest Oregon. Transitional blueschist-greenschist facies assemblages are widespread in mafic schists in the structurally lowest levels of the window; structurally higher CMS near the window margins contains medium- to high-pressure greenschist facies parageneses. An /sup 40/Ar//sup 39/Ar crossite age indicates a late Middle Jurassic age of metamorphism. Pressure-temperature estimates for the overlying CMS greenschists suggest temperatures similar to those in the central part of the window, but at slightly lower pressures. Thrusting of the overlying amphibolites at 150-156 MA occurred while the amphibolites were above about 500C. Stretching lineations indicate a movement vector of about N45W. Comparisons of the sequence and timing of metamorphic and structural events, radiometric ages, and movement directions during thrusting indicate the CMS does not represent an inlier of Kalamath Western Jurassic Belt flysch but is instead an older, isolated thrust plate. Similarities with the age of metamorphism and plutonism in the overlying amphibolites suggest the two plates may be remnants of the same Middle Jurassic paired metamorphic belt.
- Research Organization:
- Texas Univ., Austin (USA)
- OSTI ID:
- 6904543
- Country of Publication:
- United States
- Language:
- English
Similar Records
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Related Subjects
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AGE ESTIMATION
AMPHIBOLITES
ARGON 39
ARGON 40
ARGON ISOTOPES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CALIFORNIA
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
FEDERAL REGION IX
GEOLOGIC DEPOSITS
GEOLOGIC HISTORY
GEOLOGIC STRUCTURES
ISOTOPES
LIGHT NUCLEI
METAMORPHIC ROCKS
METAMORPHISM
MOUNTAINS
NORTH AMERICA
NUCLEI
ORIGIN
RADIOISOTOPES
RESERVOIR PRESSURE
RESERVOIR TEMPERATURE
ROCKS
SCHISTS
STABLE ISOTOPES
TECTONICS
USA
YEARS LIVING RADIOISOTOPES