Ph.D. / Louis Agassiz first raised the concept of a global ice age followed by an intriguing history of both proponents and opponents of the idea simultaneously contributing towards the evolution of geological notions up to the present-day ‘Snowball Earth’ model. The causes of glaciation and the sedimentary, geochemical and stratigraphic feedbacks subsequently received renewed interest. Different deposits of possible Neoproterozoic glacial successions were thus selected for detailed provenance analyses in this study. The successions selected are the Puncoviscana Formation on the Pampia Terrane (Northwestern Argentina), the Sierra del Volcán diamictite of the Tandilia System on the Río de la Plata craton (Eastern Argentina), the Kaigas and Numees Formations of the Richtersveld and Gariep areas on the Kalahari craton (Northwest South Africa and Southern Namibia) and the Karoetjes Kop Formation and Swartleikrans Bed of the Bloupoort Formation of the Vanrhynsdorp region on the Kalahari craton (Western South Africa). Diagnostic physicochemical aspects are utilized to ascertain whether the deposits studied are firstly of glacial derivation and, secondly, to constrain the provenance of every deposit. The latter culminate with identification of a regionally or globally significant event. The Sierra del Volcán diamictite is a glacial diamictite with a depositional age younger than 485±2 Ma and is correlatable with the Upper Ordovician Pakhuis Formation (Table Mountain Group) in South Africa. The recognition of a glacial deposit of Upper Ordovician age in eastern Argentina suggests that the Hirnantian ice sheet cover extended from southwest South Africa to eastern Argentina, stretching from the central Paraná basin across into central and northwest Argentina and southern Bolivia. A proximal glacial marine depositional environment is inferred within a subaqueous outwash fan deposited by sediment gravity flow. Periglacial deposits occur in the Pakhuis Formation, suggesting that the ice sheet had retreated with deposition in glacial outwash plains by braided river systems and windblown loess.

From introduction: Vein-type mineralization, particularly gold, copper, tin and tungsten has provided a source of metal to man for over 2000 years. These deposits are usually small but in some cases are of very high grade. Prior to 1940 veins were extremely important sources of metals because of their relatively high-grades. However, with improved mining, smelting and concentrating methods, much lower grade material became economic, hence these smaller deposits could no longer hold their dominance. Recently the energy crisis and escalating costs of capital for large projects has made smaller deposits attractive once more (Temblay and Descarreaux, 1978) . At the present time gold, tin and tungsten command high prices on world markets. It is for these reasons that a study of the evaluation techniques pertaining to these deposits has been undertaken. In this review the geological factors which influence the evaluation are stressed. In particular, emphasis is placed on the emplacement of vein deposits, and the subsequent chemical and structural modifications of these deposits. The latter part of the review concentrates on the limitations of the sampling and ore reserve techniques that can be applied to the evaluation of mineralized veins. In the conclusion those techniques that are most applicable are stressed, and an evaluation model is outlined.

The origin of diamonds, their preservation and transport to the surface have been important issues over the last decades after the acknowledgement that diamonds are xenocrysts in the host kimberlites and after the discovery of new transport media such as lamproites. Different types of diamonds -E-type diamonds, P-type diamonds- and different types of hosts - Eclogites, Peridotites- have been distinguished. Each type corresponds to particular formation criteria. Ecogitic Diamonds are mostly related to subduction processes, whereas more uncertainties remain regarding the formation of Peridotitic Diamonds. Komatiite extraction and subduction of graphite-bearing serpentinites have been proposed as the more likely processes involved in their formation. A typical mantle signature for diamonds implies a thick, cool, reduced lithosphere. The keel-shape model is the most popular. Archaean cratons are therefore the most promising exploration target and area selection will expect to follow the Clifford's Rule. However, the evidence of cratonic areas hidden under younger formations · through seismic profiles and the discovery of diamond structurally trapped outside their stability field, have increased the potential of diamondiferous areas. Preservation of diamonds inside the lithosphere requires that the mantleroot remains insulated against excessive reheating and tectonic reworking. Mantle-root friendly and mantle-root destructive structures are distinguished. Small-size cratons are usually the most promising exploration targets. Transport of diamonds to the surface is dependant on' the same criteria of preservation. Only kimberlites and lamproites have been recognized as efficient transport media. Their ascent to the surface is conditioned by a multitude of parameters, amongst them the nature of the magma, the speed of ascent, the presence of pre-existing structures in the crust and the availability of ground water in the near-surface environment. The origin of kimberlite magma probably lies near the transition zone. Mixtures of depleted asthenospheric · sources and metasomatically enriched and possibly subducted materials are likely to be at the origin of the different kimberlite magmas. Kimberlite magmatism correlates generally in time with global tectonic events, triggered by either plume activity or by subduction processes, depending of the tectonic school of thought. Kimberlite alignments have been interpreted as hotspot tracks, and kimberlite magmas as volatile-rich melts issued from the remaining plume tail. The plume head produces flood-basalts in an adjacent "thinspot" of the lithosphere, generally on the edges of the cratons. Kimberlite and lamproite ascent to the surface are unconditionally influenced by regional structures. Rift structures, ring structures, transform faults, suture zones and deep-seated faults have been mentioned as controlling or accompanying features of kimberlite magmatism. Nearsurface emplacement constraints are better understood and the ultimate shape of the intrusion(s) depends on the nature of the country rocks, the availability of ground water and the near-surface faulting pattern. The recent discovery of "fissure" kimberlites is one of the more important breakthroughs of the last decade. With a better understanding of the processes involved in diamond formation, preservation and of kimberlite emplacement, major diamond discoveries have recently increased on all the continents. Successful diamond exploration requires today an integration of all geophysical, petrologic, geochemical and structural information available. The particular study of the northwestern Australian lamproite and kimberlite fields, the Brazilian kimberlites, the easternNorth American kimberlite fields, the Lac de Gras kimberlite field, the South African rich kimberlite provinces, and the Yakutian kimberlite fields provide concrete examples of the geotectonic controls on primary diamond deposits. Area selection criteria based on the previous models and examples, are expected to yield to many more discoveries in the coming years. / KMBT_363 / Adobe Acrobat 9.54 Paper Capture Plug-in

The alluvial diamond deposits along the Vaal River, between Barkly West and the Vaal-Harts confluence, have been worked for more than one century by thousands of private diggers. The diamonds are recovered from two sedimentary units of Cenozoic age, the Older Gravels and the Younger Gravels. These rest on a basement of Ventersdorp Supergroup andesites and Karoo Sequence sediments, which have been intruded by Cretaceous kimberlites. The gravels are, in turn, overlain by the Riverton Formation and the Hutton Sand. On a large scale, tectonic setting, geomorphology and palaeoclimate have played a major role in the formation of diamondiferous placers in the area under investigation. A study of the sedimentology of the Younger Gravels was carried out with the aim of acquiring an understanding of the processes responsible for the economic concentration of high quality diamonds. An investigation of facies assemblages, clast composition, clast size, palaeocurrent directions external geometry, particle morphology and led to the conclusion that the Younger Gravels were deposited in a proximal braided stream environment during high discharge. A small-scale experiment was carried out to test the efficiency of different sedimentological trap sites in concentrating kimberlite indicator minerals. The results show that the concentration of indicator minerals is dependent on the size fraction chosen, bed roughness and gravel calibre. The examination of surface features on pyrope, picroilmenite and chrome diopside from kimberlite led to the conclusion that most of these minerals are locally derived. Diamond grade variations within the Younger Gravels are influenced by a combination of factors, including bed roughness, channel width and sorting process from the source. Alluvial diamond exploration programmes must take into account the tectonic setting, the palaeoclimate, the level of erosion, the stability of the drainage system in the area as well as the presence of local trap sites in the river profile. It is concluded that the diamonds are the product of a long and complex process of erosion, reworking and concentration and are derived from Cretaceous kimberlites in the area.

The thermal fouling data of Watkinson were recomputed on the assumption that increases in pressure drop were caused entirely by roughness of the fouling deposit and not at all by blockage. The results indicate that roughness played some role in the sand-water runs, but no role in the gas oil runs. The anomalous increases in overall heat transfer coefficient with degree of fouling in the first two sand-water runs were thus explained by the effect of roughness on liquid film heat transfer coefficient. The original loop was modified, the principal change being the replacement of the manual temperature recording system by a digital Data Logging System. Fluid and wall temperatures, as well as differential pressure, could thus be automatically recorded as a function of time. Better control of independent operating variables such as fluid velocity, inlet temperature and heat flux could therefore be achieved, and the effects of temporary fluctuations in these operating conditions could be observed and separated from fouling effects. Thermal fouling runs were made in the modified heat transfer loop on samples of Bayer Process spent liquor from the ALCAN aluminum refinery in Arvida, P.Q. The only discernible trends in the results were increases in rate and degree of fouling with increasing heat flux to a maximum value, followed by a sharp decrease, at liquor velocities less than 5 ft/sec, and the absence of thermally detectable fouling at higher velocities. The unreproducibi1ity of the results is believed to be attributable, at least in part, to changes in chemical composition of the liquor throughout the experiments. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

Lead isotope analyses of galena from multiple ore deposits restricted to specific tectono-stratigraphic terranes can provide information on the age and origin of the lead. In this thesis, three separate studies of lead isotopes applied to the metallogenesis of parts of the Canadian Cordillera are presented. Lead isotope data from quartz-gold vein deposits and volcanogenic and related deposits in the Insular Belt group plot in four distinct clusters on Pb-Pb plots. Each cluster corresponds to a specific deposit type and host rock category. Two parallel evolutionary trends in the lead isotopic composition exist: 1) Sicker-hosted volcanogenic deposits to Sicker-hosted veins, and 2) Karmutsen and Bonanza-hosted volcanogenic and related deposits to Karmutsen and Bonanza-hosted veins. The trends indicate a genetic relationship between host rock and isotopic composition. These observations favour a host rock source for the lead in vein deposits and, by association, a comparable source for the gold. Plutonic or abyssal direct sources of metals are not consistent with the lead isotopic data. It is suggested that the gold was extracted from the country rock, and concentrated as veins by hydrothermal activity related to Tertiary plutons. Vein deposits are isotopically distinct from volcanogenic and related deposits, providing an empirical test for distinguishing syngenetic from epigenetic deposits. Karmutsen and Bonanza-hosted deposits are more depleted in 207Pb than similar deposits in Sicker Group rocks, indicating significantly different sources for volcanic components of these two important rock units. Lead isotope data from quartz-gold veins in the Cariboo area of the Omineca Belt, and from similar veins in the adjacent Intermontane Belt indicate that these two vein types are genetically unrelated. A mid-Mesozoic model age calculated for the Cariboo gold mineralisation event indicates that all of the deposits examined are clearly epigenetic, despite reported stratiform textures at the Mosquito Creek mine. K-Ar dates from a quartz-barite vein and from regionally metamorphosed phyllite support a synmetamorphic origin for the veins, but a distal plutonic origin is not ruled out. Recent work by Godwin and Sinclair (1982) has shown that syngenetic, shale-hosted, sedimentary exhalative deposits in the autochthonous part of the Canadian Cordillera contain lead which has evolved in a high U/Pb environment. This 'shale' curve evolution model applies to deposits which have an upper crustal (host-rock) lead source. Ainsworth-Bluebell, Carmi and Slocan camps, and lead associated with the Moyie intrusions, all contain lead which plots substantially and variably below the 'shale' curve. Their departures from this curve provide evidence for a second, uranium poor, possibly lower crustal lead source, for which a growth curve, referred to as the Bluebell curve, can be constructed. The lead data are interpreted within the framework provided by these two growth curves. Mixing of lead between these two lead reservoirs is proposed to explain the linear array of data from Slocan and Carmi camps. Mixing lines, joining points of equal time on the two growth curves, provide a method for interpreting lead data from these deposits. Introduction of relatively unradiogenic lead into the upper crust via magmas which originated in the lower crust is invoked to explain the mixing. The three studies considered here illustrate the differences in lead isotopic characteristics of different tectono-stratigraphic terranes and show that the development of local models for the interpretation of common lead isotope data has application to exploration. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The apatite crystal structure-A5(TO4)3X-allows for complex substitutions of various minor and trace elements including volatile constituents, rare earth elements, and redox sensitive elements (e.g., As, Mn, Fe, S) (Piccoli and Candela, 1994; Piccoli and Candela, 2002; Pan and Fleet, 2002; Teiber et al., 2015; Harlov, 2015). In this study, apatite grains from 19 intrusions across northeastern Nevada with varied petrogenetic and metallogenic properties were analyzed by electron probe microanalysis (EPMA) to obtain major and trace element abundances. Systematic variations in Sr and REE concentrations in apatite grains from granitic host rocks are the result of competition with pre-existing and coexisting minerals in silicate melts. The presence of zoning in cathodoluminescence colors combined with high Sr concentrations in apatite from many of the Eocene granodiorite rocks suggest magma mixing affected the geochemical evolution in many of the Eocene igneous systems. In addition, high Sr concentrations in apatite grains from Late Cretaceous two-mica granites may reflect significant magmatic input from lower crustal and/or mantle sources despite the felsic nature of these intrusive rocks.A new EPMA analytical routine to measure arsenic down to detection limits of approximately 20 ppm allowed a more extensive characterization of As concentration in igneous apatite than has previously been published. Still, correlations between As and other trace-element concentrations are not evident, which may reflect the simple substitution of As5+ for P5+ in the apatite structure. Petrologic controls on As content include redox state, indicated by the high Asapat/Asbulk-rock in relatively oxidized intrusive rocks. An additional control is competition among other magmatic phases, exsolving aqueous fluids, or sulfide melts, indicated by enrichment of As in apatite cores relative to apatite rims. Past studies on redox-sensitive elements in igneous apatite have focused on Mn and S, but with further investigation, As may also prove to be a key redox-sensitive trace element in apatite for interpreting igneous and hydrothermal processes.

Bibliography: p. 420-430. / In this thesis the processes that produced diamond placer deposits within closed endoreic basins along the west coast of Namibia are addressed. These deposits, first discovered in 1908, and documented by Kaiser in 1926, occur in an area of wind deflation between latitudes 26 and 28 degrees South. Salt rock weathering and aeolian abrasion has eroded elongated depressions that are up to 120 m deep, that happen to be parallel with the dominant wind flow from the south and south-southeast, which governs aeolian processes in the coastal tract. The velocity of winds from the south and south-southeast frequently averages 50 to 60 km/hour between October and March, and gusts at 80 to 90 km/hour. At these velocities, grains exceeding -1 phi (2 mm) in diameter are commonly entrained into the saltation load above stone pavement surfaces, making this an extremely active aeolian environment.

El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / In the mining industry, due to the extraction and processing of ore, a significant amount of tailings are produced which are discharged into deposits. In some cases, these are in contact with effluents and generate acid waters that pollute the environment and affect the health of the inhabitants. Additionally, these tailings within their composition contain valuable metals that can be reused through a process of mineral flotation. As a part of this research, a study based exclusively on laboratory tests was performed on the tailings deposit located in the Recuay–Peru district, where the presence of concentrations of Pb, Zn, and Ag at 48.36% was obtained, 23% and 250 g/TM. Thus, this study aims to take advantage of polymetallic tailings deposits that are in an abandonment state by extracting valuable ore through the flotation process based on their chemical composition and mineralogical characterization.

Sand boil formation due to underseepage is a potential failure mechanism for levees in the Lower Mississippi River Valley. Sand boils were identified in the Buck Chute study area in the 1990s during high water events and during the 2009 Flood. The site is unique due to the presence of point bar and abandoned channel deposits. To understand the role of these alluvial deposits on sand boil formation at the site, a geologic investigation of the subsurface was conducted. Using shallow geophysics, cone penetrometer tests (CPT), borings, and a geographic information system (GIS), it was concluded that the thin blanket associated with point bar deposits, abandoned channel deposits causing a blocked seepage path, and head differential changes caused by the Muddy Bayou Control Structure were the controls of sand boil formation at Buck Chute.