Thesis (M.S. in Earth and Environmental Sciences)--Vanderbilt University, Aug. 2008. / Title from title screen. Includes bibliographical references.

Thesis (B.S.)--University of Missouri, School of Mines and Metallurgy, 1900. / The entire thesis text is included in file. Typescript. Illustrated by author. Title from title screen of thesis/dissertation PDF file (viewed December 22, 2008)

No description available.

The mechanism of emplacement of ultramafic intrusions has been a controversial subject for many years. This thesis summarizes evidence favoring the intrusion of ultramafic rocks as magmas. Experiments were conducted to study the effect on the melting behavior or ultramafic rocks of carbon dioxide, sodium, sulphur and water at temperatures up to 925°C. and pressures up to 2125 atmospheres. No melts were produced but it is felt that the evidence presented justifies further work on the problem. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

Four olivine gabbro plugs crop out on the basaltic plateau in the south Cariboo region of British Columbia. The plugs form elliptical knobs of unaltered gabbro which stand 100 to 200 feet above the plateau surface. They are 300 to 600 feet in greatest diameter, as seen in plan view. Two plugs, Mt. Begbie and Forestry Hill, are described in detail in this thesis. Alignment of tabular feldspar grains resulting from the upward flow of magma, has produced a foliation in both Mt. Begbie and Forestry Hill plugs. Foliation dips toward the centre at moderate to steep angles in both plugs. Small, scattered lenses of leucogabbro and picritic gabbro lie approximately in the plane of foliation. Marginal foliation is assumed to be roughly parallel to the walls of the plug. Foliation trends indicate that both plugs are funnel-shaped, increasing in diameter toward the surface. The essential minerals of the plugs are olivine, calcic-augite and plagioclase. They are strongly zoned indicating a disequilibrium environment of crystallization. From a consideration of mineralogical and chemical characteristics it is concluded that the original magma was an alkali basalt magma. Differentiation by fractional crystallization produced small volumes of marginal dolerite and pegmatitic gabbro in the outer portions of Mt. Begbie plug. The trend of differentiation leads to iron-enrichment in the marginal dolerite, and then to alkali-enrichment in the pegmatitic gabbro. The four plugs occupy former volcanic vents which, in late Tertiary time, fed lava to the surrounding plateau. The exposed portions of the plugs crystallized possibly within 50 to 150 feet of the surface. General geological relationship, petrological similarity, and the close comparison of fused whole-rock powders suggest a definite kinship of the plugs to the surrounding basaltic lava. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Digitized by Kansas State University Libraries

Call number: LD2668 .T4 1953 B7 / Master of Science

No description available.

published_or_final_version / Earth Sciences / Master / Master of Philosophy

The unique Selukwe Subchamber of the Great Dyke is bounded by the Shurugwi greenstone belt (SGB) on the west side for approximately 25 km and granitoids on the east side, as compared to other subchambers of the Great Dyke that are bounded on both sides by granitoids. It is also the narrowest section of the entire Great Dyke. The extensive xenolith suite is found on the western flank and the central zone of the subchamber. This study focuses on the PAR 11 borehole and the surface xenoliths in the Selukwe Subchamber (SSC). The PAR 11 core was drilled into an anomalous sequence of ultramafic rocks situated in the Mafic Succession of the SSC. There are basically two rock types in the PAR 11 borehole: peridotites and pyroxenites. Comparison of the major and trace element geochemistry of the PAR 11 body with the MR 92 data of Coghill (1994) for the SSC reveals that they are similar but less evolved. The mineral assemblages and proportions of phases in the PAR 11 borehole samples are indicative of essentially the same composition as that which formed the layered sequence of the Great Dyke. Therefore, on the basis of the rock types and chemical compositions, the PAR 11 body and the Great Dyke cumulates appear to be petrologically and chemically similar and had the same petrogenesis. There are three rock types in the xenolith suite that have been observed in the mafic succession of the Unki area: peridotites, pyroxenites and gabbros. Major and trace elements show a wide range of compositions that have CaO/Al2O3 ~ 1, which are dissimilar to both PAR 11 and MR 92 borehole data. REE patterns show depletion of LREE, with flat HREEs indicating a different magma to that which gave rise to the Great Dyke. Such flat patterns are typical of a primitive mantle source similar to that of komatiite magma. Stowe, (1974) describes dunite and chromite in the SGB and does not describe pyroxenites and gabbros. Therefore, it is not clear in the first instance that the xenoliths were derived from the SGB. It also does not necessarily mean that these rock types did not occur in the SGB and, if they did, maybe they were derived from an intrusion within the SGB that is at depth and never been seen iv before. The xenoliths do not have mineral compositions that are similar to the Great Dyke and therefore precludes them as having been derived from the Great Dyke Marginal Facies, a possible source of such rocks. Therefore, it is concluded from this study that they were inherited from another source which also does not appear to be the SGB because there is no report of such rock types (other than peridotite) in the SGB. They are also not mantle derived. The metasedimentary rocks that occur as xenoliths are banded iron formation and quartzites and are all clearly derived from the different formations of the SGB. The quartzites are from the Mont d’Or Formation and Wanderer Formation. The BIFs are from the Upper Greenstone and Wanderer Formation. The Shurugwi Greenstones were stripped off from the western flank whereas the Archean granitoids to the eastern flank of the Great Dyke remained. The conclusion from this study is that the Shurugwi greenstones and Archean granitoids of the Selukwe area were intruded by the large volume of new magma that was the parental magma to the Great Dyke. The hot parental magma carried up with it xenoliths from outside the Great Dyke and large blocks from within the Great Dyke to the uppermost rocks of the level of the P1 pyroxenite layer and mafic unit.