Award Date

1-1-2005

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Geoscience

First Committee Member

Eugene I. Smith

Number of Pages

116

Abstract

The Pine Valley Volcanic Field in southwestern Utah consists of at least 24 mafic lava flows and 10 vents. Eruptions have spanned the past 2.4 m.y. The youngest eruptions at the Snow Canyon and Diamond Valley cones occurred between 1 and 20 ka. Lava flows range in composition from basalt to andesite, and include both alkaline and subalkaline rocks throughout the field. Trace element abundances for the youngest lavas show both oceanic island basalt (OIB) and mid-oceanic ridge basalt (MORB) components in their source. Sr and Nd isotopic ratios exhibit evolved values, spanning a large range from epsilon Nd of 0.54 and 87Sr/86Sr of 0.7036 to epsilon Nd of -7.83 and 87Sr/86Sr of 0.7055. The apparent conflict between geochemical evidence for an asthenospheric source (MORB and OIB-like trace element abundances) and a lithospheric source (evolved isotopic ratios) is resolved through a model that calls upon contamination of an asthenospheric melt with ancient (isotopically-evolved) mid-oceanic ridge basalt (MORB) within the lithosphere.

Keywords

Basalt; Field; Flows; Geochemistry; Petrogenesis; Pine; Pleistocene; Pliocene; Relationship; Tectonics; Transition; Utah; Valley; Volcanic; Zone

Controlled Subject

Geology

File Format

pdf

File Size

3737.6 KB

Degree Grantor

University of Nevada, Las Vegas

Language

English

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