Award Date

1-1-2002

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Geoscience

First Committee Member

Terry L. Spell

Number of Pages

151

Abstract

Thermochronologic data and geobarometry from the Granite Mountains indicate exhumation of mid-crustal plutons during Late Cretaceous extensional tectonics. U/Pb zircon and 40Ar/39Ar ornblende ages indicate intrusion, crystallization, and geologically instantaneous cooling through 500°C at ∼75 Ma. K-feldspar multi-diffusion domain modeling indicates a cooling rate gradient from SW to NE of 63, 32, and 16°C/Ma for three samples spanning a transect across the range. NE K-feldspar cooled through ∼252°C by 73 Ma while other samples remained >375°C suggesting a short lived down-to-the-east normal faulting event at ∼75 to 74 Ma. Faster cooling rates with later initial K-feldspar recording (∼71 Ma) suggest extension continued along a shallow down-to-the-southwest detachment active from ∼73 to 69 Ma. U-Th/He apatite ages suggest the Late Cretaceous extensional event juxtaposed the deeper-seated Granite Mountains plutons with the shallow-level southern Providence Mountains plutons and the two cooled through 70°C as a single block.

Keywords

California; Collapse; Complex; Exhumation; Geobarometry; Granite; Mountains; Orogen; Plutonic; Sevier; Southeast; Thermochronology

Controlled Subject

Geology

File Format

pdf

File Size

3655.68 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

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