Thesis (M.S.)--University of Georgia, 2001. / Includes bibliographical references (leaves 74-78). Also available in electronic format via Internet.

published_or_final_version / Earth Sciences / Master / Master of Philosophy

Thesis (Ph. D.)--Dept. of Geology and Geophysics, University of Adelaide, 1992. / Typescript (Photocopy). Includes copies of 4 papers by the author as appendix 4 (v. 1). Errata slip inserted. Includes bibliographical references (leaves 170-192 (v. 1)).

Thesis (M.S.)--University of North Carolina at Wilmington, 2005. / Includes bibliographical references (leaves: [131]-134)

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 337-356). Available also in a digital version from Dissertation Abstracts.

Honors Project--Smith College, Northampton, Mass., 2010. / Includes bibliographical references (p. 44-45).

No description available.

Mapping of the north-eastern portion of the Bird1s River Complex revealed that two large xenoliths composed of pyroclastic rocks and sandstone of the Cave Sandstone Stage have reacted with the dolerite. All the reaction phenomena normally associated with Karroo Dolerite are encountered. These are: (a) Metasomatism during the stage of iron enrichment of the dolerite with the production of a pyroxene-plagioclase metasomatic granophyre (b) Metasomatism during the stage of alkali enrichment of the dolerite with the production of a potassium feldspar adinole C c) Assimilation 'vi th the production of contaminated doleri tes Cd) Fusion 'vi th the production of glassy rocks including buchi tes (e) The production of rheomorphic veins

The Del Bac Hills are a northeast-trending chain composed of mid-Tertiary Turkey Track porphyry dikes and flows, overlain by potassic basaltic andesites intercalated with sediments. These hills are considered the southernmost extension of the Tucson Mountains and lie along a northeast-trending basement scarp which extends across the Tucson Basin. Turkey Track porphyry intrudes the San Xavier conglomerate as two parallel dikes, closely associated in time but with different magnetic orientations. Potassium-argon dating of a flow associated with the older dike yielded a mean of 26.8 m.y. for plagioclase phenocrysts and groundmass. Plagioclase of the younger dike sampled 50 feet from the contact with the San Xavier conglomerate and at a depth of approximately 200 feet yielded an anomalous age of 46.4 m.y., representing 0.29 x 10^-10 moles per gram excess Ar4° in comparison with the extrusive. The 21 basaltic andesite flows are essentially contemporaneous at 24-25 m.y. Tight grouping of K/Rb and Rb/Sr for the basaltic andesites confirms the field inference of two separate sources. Specific gravity and initial Sr^87/Sr^86 determinations for the porphyry and basaltic andesites do not preclude a comagmatic origin for the two rock types. Post-extrusive faulting along three principal directions has established the present configuration of the hills.

Kimberlite, an ultrabasic diamond-bearing hypabyssal rock-type which has its origin in the Earth's upper mantle, characteristically contains rare, well-rounded xenoliths of peridotite and eclogite. These xenoliths, which undoubtedly originate from some considerable depth below the Earth's surface, possibly represent samples of upper mantle material. They have received much attention from earth scientists and numerous theories as to their origin have been proposed. Forty-two selected peridotite xenoliths from the Bultfontein, Wesselton, Dutoitspan and Roberts Victor kimberlite pipes of the Kimberley area, South Africa, and 24 eclogite xenoliths from the Roberts Victor pipe have been examined in detail using a variety of petrological and mineralogical techniques. The petrologic research comprises conventional petrographic studies, the determination of accurate modal compositions and the presentation of 22 new whole-rock chemical analyses, nine of which are of garnet peridotite, four of spinel peridotite and nine of eclogite, one being a diamondiferous specimen. Detailed mineralogical studies of the constituent minerals of the xenoliths comprises descriptive mineralogy, in most cases an estimation of the compositions of these minerals from the measurement of physical properties, X-ray powder diffraction data and the presentation of 21 new chemical analyses of pure mineral separates. This includes five analyses of clivine, five of orthopyroxene, eight of garnet, one of chrome diopside and two of omphacite. The results of the investigation have shown that the peridotites consist essentially of forsterite and enstatite with minor or trace amounts of one or more of pyrope-rich garnet, chrome diopside, chrome spinel, phlogopite and rarely graphite, and often exhibit features consistent with plastic movement and tectonic deformation. The peridotites are believed to be derived from an ultrabasic upper mantle, which is both chemioally and physically zoned. The eclogite xenoliths, which are composed mainly of pyrope-almandine garnet and omphacitic clinopyroxene and occasionally contain kyanite, corundum and diamond, are not samples of a primary eclogitic upper mantle nor the products of an eclogite fractionation related to kimberlite genesis. Chemically they are not typical of extrusive basalts and probably either represent pockets of partially fractionated basic magma trapped at mantle-level in an eclogite-stable environment or samples of high-grade crustal metamorphic eclogite accidentally incorporated into the Roberts Victor kimberlite.