The sup 40 Ar/ sup 39 Ar thermochronology of the eastern Mojave Desert, California, and adjacent western Arizona with implications for the evolution of metamorphic core complexes

Journal Article · Sat Nov 10 04:00:00 EST 1990 · Journal of Geophysical Research; (United States)

OSTI ID:5262925

Foster, D A; Harrison, T M ^[1]; Miller, C F ^[2]; Howard, K A ^[3]

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1. State Univ. of New York, Albany (USA)
2. Vanderbilt Univ., Nashville, TN (USA)
3. Geological Survey, Menlo Park, CA (USA)

The application of {sup 40}Ar/{sup 39}Ar thermochronology provides information about the timing and nature of thrusting, plutonism, metamorphism, denudation, and detachment faulting. The {sup 40}Ar/{sup 39}Ar ages of 175 to 125 Ma from the Clipper, Piute, Turtle, Mohave, Bill Williams, and Hualapai Mountains are interpreted to be the result of a middle Mesozoic thermal event(s) caused by crustal thickening. The {sup 40}Ar/{sup 39}Ar data from the Clipper and Piute Mountains suggest that this thermal event was followed by a period of cooling at rates of 1-5C/m.y. Orogenesis culminated during the Late Cretaceous when rocks exposed in the Old Woman-Piute, Chemehuevi, and Sacramento Mountains attained temperatures >500C which reset the K-Ar systems of minerals from Proterozoic rocks. High-grade metamorphism in the Old Woman Mountains area was caused by the intrusion of the Old Woman-Piute batholith at 73 {plus minus} 1 Ma. Cooling rates following batholith emplacement in the Old Woman Mountains were {approximately}100C/m.y. between 73 and 70 Ma and 5-10C/m.y. from 70 to {approximately}30 Ma. By 30 Ma, rocks exposed in the Old Woman-Piute, Marble, Ship, Clipper, and Turtle Mountains were below {approximately}100C. The {sup 49}Ar/{sup 39}Ar ages from the Sacramento Mountains suggest that mylonization caused by the onset of regional extension occurred at 23 {plus minus} 1 Ma. When extension started in the Chemehuevi Mountains, rocks exposed in the southwestern and northeastern portions of footwall to the Chemehuevi detachment fault were at {approximately}180C and {approximately}350C, respectively. Unroofing of the footwalls to detachment faults in the Sacramento and Chemehuevi Mountains resulted in average cooling rates of 10-50C/m.y. between 22 and 15 Ma.

• OSTI ID: 5262925
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 95:B12; ISSN JGREA; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
AGE ESTIMATION
ALKALI METAL ISOTOPES
ARGON 39
ARGON 40
ARGON ISOTOPES
ARID LANDS
ARIZONA
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CALIFORNIA
CONTINENTAL CRUST
COOLING
CRETACEOUS PERIOD
DEFORMATION
DESERTS
DEVELOPED COUNTRIES
EARTH CRUST
EVEN-EVEN NUCLEI
EVEN-ODD NUCLEI
EXTRUSION
FABRICATION
FEDERAL REGION IX
GEOLOGIC AGES
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC HISTORY
GEOLOGIC STRUCTURES
ISOTOPE DATING
ISOTOPES
LIGHT NUCLEI
MATERIALS WORKING
MESOZOIC ERA
METAMORPHISM
MINERALS
MOUNTAINS
NORTH AMERICA
NUCLEI
OROGENESIS
POTASSIUM ISOTOPES
PRECAMBRIAN ERA
RADIOISOTOPES
RESERVOIR ROCK
RESERVOIR TEMPERATURE
STABLE ISOTOPES
TECTONICS
USA
VOLCANISM
YEARS LIVING RADIOISOTOPES