Thesis (M.S.)--Oregon State University, 2003. / Includes folded maps in pocket. Typescript (photocopy). Includes bibliographical references. Also available online.

No description available.

Thesis (Ph. D.)--Oregon State University, 2000. / Typescript (photocopy). Includes bibliographical references. Also available on the World Wide Web.

Thesis (M.S. in geology)--Washington State University, May 2010. / Title from PDF title page (viewed on June 23, 2010). "School of Earth and Environmental Science." Includes bibliographical references (p. 87-96).

An extensive suite of hydrothermally altered basalts, gabbros, and plagiogranites, was recovered from the trench-facing slope of the Tonga forearc. The tectonic setting, lithology, and geochemistry of these samples make them a unique collection for comparison with suprasubduction zone (SSZ) ophiolites. Petrography, mineral chemistry, and geothermometry are used to constrain the metamorphic evolution of ocean crust formed in a modern SSZ setting. We report the discovery of the first suite of oceanic epidosites. Tongan epidosites metasomatically replaced basaltic and plagiogranite protoliths and formed under similar conditions to epidosites hosted in many SSZ ophiolites. The range of alteration temperatures and mineral assemblages in basalts and gabbros are similar to those described from both SSZ ophiolites and mid-ocean ridges (MORs). However, the degree of alteration in basalts and the presence of epidosites in the Tonga collection are most similar to alteration characteristics in SSZ ophiolites. We show that the trace element chemistry of epidote may be linked to the composition of fluids circulating deep in hydrothermal systems. This is possible due to the subordinate role crystal chemistry may play in controlling the trace element chemistry of hydrothermal minerals. Whole rock oxygen isotope ratios of the Tonga samples are generally similar to values determined from MOR and SSZ ophiolite samples; however, enriched values in plagiogranites and gabbros may indicate a late, low temperature metamorphic overprint associated with tectonic unroofing during trench rollback. Basalts show an interesting northward decrease in oxygen isotope ratios that remains unresolved. / Graduate

Thesis (doctoral)--Universiteit Utrecht, 2007. / Includes bibliographical references (p. 99-104).

Thesis (M.Sc.)--Acadia University, 2001. / Includes bibliographical references (leaves 151-156). Also available on the Internet via the World Wide Web.

Thesis (M.S.)--University of Nevada, Reno, 2006. / "December, 2006." Includes bibliographical references (leaves 55-60). Online version available on the World Wide Web.

M.Sc. / A prominent zone of deformation, identified as a possible hydrothermal fluid pathway, has recently been discovered by the author in the 64 SW4 21Line workings at Kopanang Gold Mine. The zone is between 3m and 16m wide, has a NE SW trend and dips steeply (65°-70۫°) towards the SE. Very little to no displacement seems to occur along this zone of alteration that is marked by intensive albite veining; the surrounding host rocks are also intensively altered (albitized). Albitization resulted from sodium metasomatism, during which Na was exchanged for K, and was accompanied by quartz dissolution which resulted in vug formation. This alteration event is also characterized by REE enrichment, which was found to be most intense in carbonate (ankerite) rich albitized vein fill material. A study of fluid inclusions indicates that the main hydrothermal fluid was of relatively low salinity (14.46 to 19.84 wt% NaCl ), having homogenization temperatures between 59.6 and 117°C. From these measurements it was concluded that a likely emplacement temperature for the studied feature would be in the order of 200°C-300°C at a pressure of roughly 0.5 to 1Kbar. A marked increase of Au grades is observed where the Vaal Reef, the most important economical reef horizon exploited at the mine, is affected by deformation, veining, and associated alteration. In light of the above observations it appears only reasonable to expect that this zone of deformation and hydrothermal alteration could either be the direct cause of, or at least have a prominent influence on the high gold values occurring in the area. A causal link between high Au grades, deformation and hydrothermal fluid flow would have obvious economic implications. The study therefore strives to characterise the extent and style of deformation, constrain the effects of hydrothermal alteration and nature of hydrothermal fluids associated with the structure, and assess its importance for Au mineralization

No description available.