Award Date

6-2006

Degree Type

Thesis

Degree Name

Master of Science in Geoscience

Department

Geoscience

First Committee Member

Eugene Smith, Chair.

Number of Pages

130

Abstract

The basalts of the Norris-Mammoth corridor within the Yellowstone Plateau volcanic field have an outcrop erupted volume of ~94 km3. Basalt in the Yellowstone Plateau volcanic field is minor in volume compared to 3,700 km3 of felsic lavas, domes, and pyroclastic rocks. The tholeiitic eruptive products formed small Hawaiian-style shield volcanoes. A newly identified volcanic vent, called the Panther Creek vent, within the Swan Lake Flat basalt stratigraphic unit, was primarily Strombolian in its eruption style. This vent is the first recognized cinder cone in Yellowstone National Park.

All basaltic units within the Norris-Mammoth corridor, and the Yellowstone Plateau volcanic field, can be differentiated by isotopes and trace element geochemistry. This suggests that independent partial melting events of asthenospheric mantle were responsible for the petrogenesis of the basalts within the Norris-Mammoth corridor. The simplest model to explain the genesis of the youngest basalt unit (Swan Lake Flat basalt that erupted from the Panther Creek vent) in the Norris-Mammoth corridor is one of "source mixing." Partial melting produced EMORB-like basalt in the upper mantle. This basalt was contaminated or mixed with older, fractionated basalt within the lithospheric mantle.

More precise ages for post-Yellowstone caldera basalts, along with accurate Nd and Sr isotopes show a general decrease in 87Sr/86Sr and increase in ENd with decreasing age of Norris-Mammoth corridor basalts. This suggests that the basalts in the Norris-Mammoth corridor may be recording a new influx asthenospheric partial melts into the overlying lithosphere. Pooling of multiple basaltic partial melts in the lithosphere may be melting surrounding crust, generating rhyolitic magma that may coalesce to form a batholith-sized magma chamber and produce a new caldera cycle.

Keywords

Basalt—Analysis; Petrogenesis; Pleistocene Geologic Epoch; United States--Yellowstone National Park; Volcanic ash; tuff; etc.

Disciplines

Geology | Volcanology

Language

English

Comments

Best copy available.

Incomplete paper data.

Refer to PDF file for exact formulas.


Share

COinS