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This thesis presents the results of a detailed study of the mineralogy and paragenesis of gold at the Sunrise Dam gold deposit. The Sunrise Dam mine is the largest gold deposit in the Archean Laverton Tectonic Zone of the Eastern Goldfields Province, Yilgarn Craton, Western Australia. A number of previous studies have established the geology, geochemistry and geochronology, but the nature of the gold mineralogy and distribution has remained poorly characterized. Mineralogical studies have established a paragenetic sequence consisting of five hydrothermal stages (D1, D2, D3, D4a and D4b) which are generally in accord with the major deformation events at Sunrise Dam gold deposit. The D4a stage was the dominant episode of Au deposition, followed, in importance by the D4b stage, which is characterized by more diverse ore mineralogy including base metal sulfides, sulfosalts, and telluride minerals. Based on EPMA results, native gold in D4a stage has higher purity, with a small range of Ag variations (fineness 923 ~ 977, average 945), than that of the D4b stage (fineness 596 ~ 983, average 899), in which fineness values decrease systematically in accord with mineral paragenesis, reflecting that gold deposition was from a progressively compositionally evolving hydrothermal fluid with respect to Au/Ag ratios. The occurrences of As-rich pyrites are restricted to steeply-dipping ore bodies, which are most likely structurally connected at various level by channel ways through which As-rich (D4a) hydrothermal fluid migrating upward. There is a systematic variation in composition of the tetrahedrite-group minerals ranging from Sb to As end-members with highly variable Zn:Fe ratios, which correlates with the later paragenetic stages (D3, D4a, and D4b) and mineral associations. The composition of the tetrahedrite-group minerals is useful as a petrogenetic indicator of the evolution of the hydrothermal mineralizing systems with time. A total of thirteen telluride mineral species, including two unnamed phases, were identified in the D4 veins. Among them nagyágite, the complex Pb-Sb-Au tellurosulfide is most abundant. The deposit is the second occurrence of this mineral in the Yilgarn Craton. Compositionally, nagyágite from Sunrise Dam conforms to ideal stoichiometry, with negligible As content and Au/(Au+Te) ratio of 0.325. The diverse mineralogy of the post-D4 veinlets relative to the host veins is attributed to small-scale reaction fronts established along zones of replacement. The presence of Au-Ag tellurides in D4 veins and the character of their breakdown products have implications for the gold recovery as well as for the genetic interpretation of the deposit. During the D4b stage, Au-richer telluride and Au-richer native gold mineralization formed earlier than Ag-(Au)-telluride and Ag-richer gold mineralization. Values of f(Te2) and f(S2) for the early telluride assemblages were determined at 300°C to be -10.7 to -7.8 (log fTe2) and 11.4 to -8.6( log fS2 ). The Au content of arsenian pyrite and arsenopyrite from four mineralizing stages (D1, D3, D4a and D4b) was measured using in-situ LA-ICP-MS. The average Au concentration is 44.5 ppm in pyrite (n = 224) with maximum value of 3,067 ppm, and 1,483 ppm in arsenopyrite (n = 35) with maximum value of 5,767 ppm, which are the highest concentrations reported for the Yilgarn Craton. The concentrations of invisible Au in arsenian pyrite at Sunrise Dam varies with mineralizing events, mineral paragenesis, and textural type. Gold is strongly enriched in D4a stage pyrite (average 80.8 ppm) and to a lesser extent in D4b pyrite (average 16.8 ppm). Pyrite from D1 (average 3.55 ppm) and D3 (average 2.96 ppm) show much lower levels of Au enrichment. The presence of metallic Au below the Au solubility limit in the Sunrise Dam pyrite is interpreted as evidence of an epigenetic origin for Au mineralization. Small-scale remobilization during dissolution-reprecipitation (D4a) and recrystallization (post-D4b) processes resulted in the Au enrichment and the upgrading of Au during successive hydrothermal events in the deposit. The speciation of Au at Sunrise Dam and the exceptional size of the deposit are the result of multiple fluid flow and multiple Au-precipitating mechanisms over a single plumbing system.

The post-orogenic history of the Appalachian Mountains, particularly the persistence of rough topography and the degree of river incision throughout the region, has been a longstanding focus of geomorphology studies. Numerous models have been developed to explain the evolution of this landscape, variously invoking episodic or continuous processes of uplift and erosion to drive the generation or reduction of topographic relief. Recently, late Cenozoic uplift has found favor as a mechanism for rejuvenating the topography of the southern and central Appalachians. This hypothesis has drawn on longitudinal river profiles, seismic tomography, and offshore sediment records as evidence of Neogene uplift.<div><br></div><div>Radiometric dating of surficial deposits provides a means to directly test models of episodic and continuous landscape evolution, as well as the Neogene uplift hypothesis. The research described in this thesis dates surficial sediments (river terraces, alluvial fans, and a filled sinkhole) and supergene manganese oxides using 26Al/10Be burial dating and 40Ar/39Ar geochronology, respectively. Our cosmogenic 26Al/10Be dating provides detailed histories of aggradation and incision along the Shenandoah and Tennessee Rivers since the early Pliocene. 40Ar/39Ar dating of manganese oxides permits estimates of surface preservation and denudation in the Shenandoah Valley and nearby watersheds throughout the Cenozoic.<br></div><div><br></div><div>The results of our work in the Shenandoah Valley, Tennessee River basin, and intervening areas indicate that the Appalachians experienced no significant pulse of uplift during the Cenozoic. Long-term preservation of supergene manganese oxides dates as far back as the Eocene, demonstrating minimal denudation and discontinuous formation that lend evidence to episodic landscape evolution models. Cosmogenic26Al/10Be burial ages along the Shenandoah and Tennessee Rivers reveal Pliocene aggradation, with enhanced deposition in the Shenandoah Valley during the mid-Piacenzian Warm Period. Both rivers likely experienced incision during the Pleistocene, likely due to climatic fluctuations. These results demonstrate that while the Appalachian landscape has remained largely unchanged for tens of millions of years, rapid Pleistocene changes in base level recently triggered significant incision of major drainages.<br></div>