Masters Theses


"The Mt. Sheridan Roosevelt Gabbro of the Wichita Mountains igneous province in Southwestern Oklahoma underwent dynamic crystallization, resulting in three distinct gabbro zones with a range of pegmatite morphologies spread throughout. The three zones are informally named the lower, central, and upper zones. The lower zone consists of a quartz and alkali feldspar poor, plagioclase and pyroxene rich, poorly altered, gabbro cumulate. The central zone is comprised of a heavily altered quartz and alkali feldspar rich gabbro with few cumulate textures. The upper zone is mineralogically and texturally identical to the lower zone, distinguished only by its higher elevation. The presence of reversely zoned plagioclase crystals indicates changes within the magma chamber during crystallization, possibly facilitated by magma replenishment or seismic activity.

The various pegmatites found throughout the gabbro are mineralogically identical and formed from an identical evolved melt expelled from interstitial spaces within the cumulate pile during crystallization. The evolution of the pegmatite from millimeter wide interstitial diffuse pegmatite to meter wide planar dikes reflect the migration mechanisms of the evolved pegmatite melt through the cumulate pile: melt diapirs as pegmatite pods, self propagating fractures as melanocratic and leucocratic irregular dikes, and brittle fractures as zoned dikes. The migration mechanisms of pegmatite melt were dependent on the volume of melt collected and the rigidity of the surrounding cumulate pile. When a large volume of expelled pegmatite melt collected, the melt was able to buoyantly migrate upward through the cumulate pile and, if it migrated through the crystallization front, became incorporated into the active magma chamber. This resulted in the crystallization of a more evolved gabbro in the central zone"--Abstract, page iii.


Hogan, John Patrick

Committee Member(s)

Oboh-Ikuenobe, Francisca
Laudon, Robert C.


Geosciences and Geological and Petroleum Engineering

Degree Name

M.S. in Geology and Geophysics


Geological Society of America
Missouri University of Science and Technology
Sigma Xi


This thesis was published in two volumes. The first volume contains pages i through xiii and 1 through 209. The second volume contains pages 210 through 439 (Appendices B through I, Bibliography and Vita)


Missouri University of Science and Technology

Publication Date

Spring 2011


2 volumes (xiii, 439 pages), maps

Note about bibliography

Includes bibliographical references (pages 435-438).

Geographic Coverage

Wichita Mountains (Okla.)


© 2011 Daniel Russell Lasco, All rights reserved.

Document Type

Thesis - Restricted Access

File Type




Subject Headings

Gabbro -- Oklahoma
Geology -- Oklahoma -- Wichita Mountains
Petroleum -- Geology -- Oklahoma -- Wichita Mountains

Thesis Number

T 9833

Print OCLC #


Electronic OCLC #


Link to Catalog Record

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