Page 214 Not included in thesis. / <p> Hydrothermal carbonate was introduced into igneous rock in the Timmins area during an early, sea water alteration event when calcite (δ13C = 0 to -3o/oo) filled the primary porosity of basalt flows and during a later hydrothermal event when mafic and ultramafic igneous rock were altered into a zoned sequence consisting of an inner zone of ferroan or magnesian carbonate flanked by calcite- and chlorite-rich assemblages. The younger intense carbonate alteration event predated or was synchronous with regional metamorphism and deformation and was focused along structurally induced, permeable zones. Gold was introduced during and after the intense carbonate alteration.</p> <p> Away from carbonaceous sediments, δ13C-values of the ferroan carbonate are very uniform (-3.5 to -5o/oo) regardless of stratigraphic position, size, or gold tenor of the alteration zone. As carbonaceous sediments are approached, 13C of the ferroan carbonate becomes upto 4o/oo heavier. The 13C of the CO2 and δ18O and δD of the water components of the hydrothermal fluid are estimated to have been -3 to -6, +5 to +10, and -40 to -60o/oo respectively. The geological controls on the distribution of carbonate alteration, and the stable isotopic values of the hydrothermal components suggest that the H2O-CO2 hydrothermal fluid was of magmatic origin, a result of mantle degassing.</p> / Thesis / Doctor of Philosophy (PhD)

<p> Altered olivine tholeiite basalt on Mauna Ulu Volcano, Hawaii was examined petrographically and chemically to determine the mineralogy of the alteration products. Colour plays an important role in determining a general trend of alteration. </p> <p> The processes involved in the formation of Mauna Ulu have little effect on the alteration. The major influence is the type of volcanic gas and its constant interaction with the basaltic lava over an eight year period. The gas is oxidized as it cools, resulting in a zoning of different alteration products in a variety of colours and compositions. </p> <p> The major alteration phase was determined to be amorphous opaline silica. Other species present are hematite and sulphur, with minor halides, sulphates and sheet silicate (chlorite). </p> / Thesis / Bachelor of Science (BSc)

This study shows how the composition of gases released from a single magmatic source may be modified during their ascending path. The main processes that influence the composition of the gases in these high temperature fumarolic environments, are: 1) interactions with wallrocks during gas ascent, which change the fugacities of the metal volatile species and affect the equilibrium between major species (fH2S/fSO2; fH2/fH2O); 2) mixing with meteoric water with consequent Cl adsorption, which may account for the Cl depletion of the gases; 3) remobilisation of previously formed sublimates and/or incrustation deposits. Comparison between the thermochemical models and the mineralogical composition of the silica tubes at Kudryavy and Satsuma-Iwojima volcanoes suggests that high fO2 due to the mixing of the gases with air during their injection into the atmosphere significantly reduces the volatility of several trace elements (As, Sb, Sn, Na, K, Tl, Te, Se and Cd). Comparisons between the enriched metals in aerosols and in the gases suggest that Mo, Pb, Bi, Na, K, Cu, Zn or Fe, which are enriched in the gases, are preferentially deposited in the gas conduits and vents whereas the highly volatile metals (Te, Tl, Sb, As and Se) and Cd condense in the plume. This study determines the reactions that may occur during the alteration of rocks in high temperature fumarolic environments. Three different processes of alteration prevail: (1) Acidic alteration which is characterized by the complete absence of clays, because the constant supply of gases to these systems allows for the pH values of the acidic fluids to be maintained low enough to prevent the precipitation of clay minerals. Complete leaching of all cations, except Si, from the primary silicates leads to important "silicification" of the wall rock. The primary mineral cations are leached in the following order: K, Na > Ca > Fe, Mg > Al > Si, Ti. The fluids enriched in these cations circulate in microcracks at different temperatures and different redox conditions and lead to the precipitation of secondary incrustations. At Kudryavy the incrustations are mainly sulfates. At Usu the lower sulfur/fluoride ratio of the gases allows the occurrence of aluminum fluoride incrustations. The order of primary minerals dissolution (olivine > plagioclase > pyroxene > matrix glass > Fe-Ti oxides) is established for both sites studied. (2) Alteration by an oxidized volcanic gas, resulting from mixing with the atmosphere (500 to 300°C). At Kudryavy, thermochemical modeling suggests that anhydrite and anhydrous sulfates, which occur at intermediate temperatures, are formed by interactions of the rock with oxidized gas. (3) The most important outcome of this work is the identification of the features of alteration by the volcanic gas that directly reacts with the rock at high temperatures (T > 500°C). The Kudryavy rocks show evidences for mineral transformations, which occur in the presence of the volcanic gas phase. Volcanic gas directly reacts with rocks at high temperatures (T > 500°C). The gas destabilizes the primary minerals, remobilizes the rock-bearing cations, and leads to the formation of second mineral assemblages. These transformations occur in situ, without significant mobility (gain or loss) of the cations. The high temperature secondary associations are characterized by the presence of andradite, hedenbergite, hercynite, tridymite/cristobalite. Anhydrite and anhydrous Al sulfate may occur within these mineral assemblages if the gas is oxidized.

The Copiapó region in northern Chile contains numerous intrusion- and volcanichosted IOCG vein systems. These veins share many features with larger IOCG systems in the region (e.g., Candelaria, Punta del Cobre), including abundant hydrothermal magnetite or hematite ± Cu, Au, REE, and other elements, and exhibit similar styles of mineralization including voluminous breccias, stockwork, and massive veins. The relatively simple geometries and small size of veins offer advantages for study of zoning and genesis in an IOCG system; and, they also provide an interesting counterpoint to classic epithermal Ag-Au veins. The vein systems exhibit systematic patterns in the alteration and mineralization zoning in both time and space. Deeper exposures are characterized by high-temperature styles of sodic and sodic(-calcic) alteration with Fe and Cu depleted vein fill assemblages. This passes upwards through a proximal zone of magnetite-dominated vein fill with sparse to absent copper, and into a magnetite-dominated, copper-bearing portion of the vein. Copper is best developed at intermediate to shallow levels in association with the hematite-dominated portions of the system. More distal, carbonate dominated facies with minor hematite and chalcopyrite are also present. Shallow levels of the vein system may be characterized by a low-sulfur style of advanced argillic alteration, that may be stratabound, in discordant breccia bodies, or structurally controlled on faults. The assemblages differ from other ore forming environments by their lack of sulfide and/or sulfate minerals, and the abundance of hypogene iron oxide phases (hematite and/or magnetite). Vein systems are dominated by brecciation events that record repeated, cyclic pulses of mineralizing fluids. Stable and radiogenic isotopic analyses, combined with fluid inclusion and mineral phase equilibria indicate the fluids were hypersaline brines (generally >40 wt% NaCl(eq)) over a temperature range of 200º-450ºC. The shallow formation, structural styles, repeated mineralization events, and size of the IOCG vein systems have many parallels to the classic precious-metal rich Ag-Au epithermal systems. Nonetheless, the two types of veins differ in their geochemistry, reflecting the large differences in fluid salinities, commonly <10 wt% NaCl(eq) in epithermal settings as compared to 15 to > 50 wt% NaCl(eq) in IOCG systems.

Deep drilling is required to reach the geothermal fluids extracted for generation of electricity; therefore, the different rock properties and the hydrothermal alteration of the lithologies being drilled become an important factor to a conventional geothermal industry. If the correct equipment required to complete drilling is not selected, the rate of penetration (ROP) can be suboptimal, potentially increasing the cost of the project. Mechanical characterisation of hydrothermally altered rocks from geothermal reservoirs will lead to an improved understanding of rock mechanics in a geothermal environment. Core samples obtained from the Ngatamariki, Rotokawa and Kawerau Geothermal Fields covered a wide range of lithologies (ignimbrite, rhyolite lava, sandstone, mudstone, andesite lava/breccia and tonalite) encountered during drilling. A suite of non-destructive and destructive laboratory tests along with petrographical analysis were conducted on the samples. Some key findings are that samples that originated from the shallow and low temperature section of the Kawerau geothermal field had higher porosity (15 – 56%), lower density (1222 – 2114 kg/m3) and slower ultrasonic wave velocities (1925 – 3512 m/s (vp) and 818 – 1980 m/s (vs)), than the samples from a deeper and higher temperature section of the field (1.5 – 20%, 2072 – 2837 kg/m3, 2639 – 4593 m/s (vp) and 1476 – 2752 m/s (vs), respectively). The shallow lithologies had uniaxial compressive strengths (UCS) of 2 – 75 MPa, and the deep lithologies had strengths of 23 – 211 MPa. Typically samples of the same lithologies that originate from multiple wells across a field have variable rock properties because of the different alteration zones from which each sample originates. To obtain a way to relate this rock property data back to the geomechanical model, we developed a method - Alteration Strength Index (ASI) - to address the effect of hydrothermal alteration on mechanical rock properties. The index constitutes three components; the mineralogy parameter, derived from petrological analysis, alteration index (degree of alteration) and an assessment of mineral hardness; the fracture parameter, assigned based on an assessment of structural damage; and the porosity parameter, which accounts for the effect of voids. This method can be used to estimate a range of rock strengths comparable to UCS, and the ASI calibrated against measured UCS for the samples produced a strong correlation (R2 of 0.86). From this correlation an equation was derived to convert ASI to UCS. Because the ASI–UCS relationship is based on an empirical fit, the UCS value that is obtained from conversion of the ASI includes an error of 7 MPa for the 50th percentile and 25 MPa for the 90th percentile with a mean error of 11 MPa. A sensitivity analysis showed that the mineralogy parameter is the dominant characteristic in this equation, and the ASI equation using only mineralogy can be used to provide an estimated UCS range, although the uncertainty becomes greater. This provides the ability to estimate strength even when either fracture or porosity information are not available, for example in the case of logging drill cuttings. To determine the usefulness of the ASI method with drill cuttings and drilling data we compared it to two methods; mechanical specific energy (MSE) and R/N-W/D chart, both developed for the oil and gas industry, in a geothermal context. We demonstrated how they can be used to estimate a range of rock strengths for hydrothermally altered lithologies for the 800 metre long 17 inch (432 mm) diameter section of well NM8 in the Ngatamariki Geothermal Field, New Zealand. We found that MSE and the R/N-W/D charts correctly ranked relative strength to ROP for three of six lithologies, while ASI correctly ranked all six lithologies. We also show that the strength values predicted by ASI correlate to ROP better than those based on MSE or R/N-W/D. We argue that ASI is more comprehensive than these methods because it provides a range of rock strength indices for a given hydrothermally altered lithology, is based on the geology, and does not require drilling parameters (ROP, WOB, RPM, and Torque) to estimate rock strength. This is particularly important in geothermal systems where lithologies can exhibit high variability in their physical characteristics and geothermal fields tend to have widely spaced wells. Using ASI we show how hydrothermal alteration affects drilling, and when used in conjunction with a predictive geologic model, how it will aid with optimisation of drilling practices through drill bit selection. Rock failure modes are difficult to predict, and are important to rock engineering environments, which include drilling. By using rock property and mineralogy information, four modes of failure were identified – axial splitting, single plane shearing, y shaped failure and multiple fracturing - in this research. The results of this study indicate that these easily measured rock properties can be inferred to have some control over the failure mode of a sample under uniaxial loading; however it would be useful to examine these samples further at the microstructural level to determine the role of microfracturing in the occurrence of failure modes. Further research in this field has the potential to aid in drilling optimisation through the utilisation of drill bits designed to fracture rocks in the ways that they are predisposed to fail.

This project examined the effects of burning on saw mark characteristics of isolated semi-fleshed white-tailed deer (Odocoileus virginianus) long bones as a substitute for human remains. Different classes of saws were examined to determine which type of saw mark characteristics are obliterated when burned and which are not. The saw mark characteristics that were examined are superficial false start scratches, false start kerfs, and completely sectioned cuts with breakaway spurs/notches. The long bones were burned at the Boston University School of Medicine using a muffle furnace, at differing temperatures and at differing time increments. The author hypothesized that the higher the temperature and the longer the duration of bone burning, the greater will be the obliterative effect on saw mark characteristics. All samples were examined using a Motic® Digital Light Microscope 12 VDC with a Nikon® MKII Fiber Optic Light attached with accompanying Motic® imaging and measuring software. Distances were measured between striations on complete cuts, false start kerf widths, and false start scratch widths using the Motic® imaging and measuring software. Images were also taken of the cross sections of the kerf floors. The striations on the kerf walls, false start kerf widths, and false start scratch widths were compared to the control samples. Measurements taken from false start scratches, false start kerfs, and complete cuts were averaged and compared to the averages from each temperature and the control samples, to assess the degree of shrinkage from thermal alteration. The false start kerf profile shapes were blindly examined and classified into Class A, B, C, or D(following the system of Symes 1992) and compared to the control samples. Kerf flare and blade drift were examined to determine if thermal alteration obliterated those saw mark characteristics. The chainsaw false start kerfs and complete cuts were examined macroscopically to determine what effects thermal alteration had on those types of marks. All thermally altered samples were assessed for color change, heat-related fracturing, and whether or not the saw marks were still visible. The author found that all saw marks made with the mitre saw, crosscut saw, and bow saw were still visible and identifiable, even in a fractured state and, when burned up to 700°C for one hour. Most of the false start kerf samples were classified into the correct kerf profile shape as outlines in Symes (1992). False start kerfs and complete cuts made with the chainsaw were blindly examined and showed that these marks are distinct and easily identifiable when the bone is completely intact or has very minimal fracturing. The crosscut saw false start scratch and crosscut saw complete cut samples showed signs of shrinkage. The average width of the false start scratch samples burned at 700°C for one hour was about 50% smaller than the control sample's average width. The same was true for the complete cut striation widths. Shrinkage did not appear to alter the crosscut saw false start kerf widths or the bow saw false start scratch widths. For all cuts made with the mitre saw shrinkage did appear to alter the samples. Warping did occur where some of the burned averages were larger than the control sample averages. This suggests that some warping did take place by widening the kerf, thus changing the analysis of the saw mark characteristics. Blade drift and kerf flare were seen in the samples and thus were not affected by thermal alteration. The author's hypothesis was not rejected, because in some cases thermal alteration did modify the saw mark characteristic measurements and in some cases thermal alteration did not alter the measurements. Some of the saw marks were affected by shrinkage, while others were not. False start kerf profile shape classification was not affected by thermal alteration. The chainsaw samples were affected most by the thermal alteration, because of the obliterative effects of heat-related fracturing which progressed generally with the greater temperature.

Orientador: Antenor Zanardo / Banca: Jorge Silva Bettencourt / Banca: Roberto Peres Xavier / Banca: Sebastião Gomes de Carvalho / Banca: Maria Margarita Torres Moreno / Resumo: A Mina Granusso está situada nas proximidades de Cordeirópolis/SP e constitui uma fonte importante de matéria-prima para o Pólo Cerâmico de Santa Getrudes. No local aflora uma sucessão de rochas da Formação Corumbataí (Permiano Superior) constituída na base por lamitos maciços que gradam para ritmitos siltosos, passando para um horizonte psamo-pelítico e culminando em uma seqüência de ritmitos siltoarenosos. Uma feição particular é a presença de zonas de alteração hidrotermal, associadas a veios quartzo-carbonáticos e fraturas, que impuseram às rochas alterações químicas, mineralógicas e texturais. Estudos petrográficos, químicos e de DRX indicam que após a compactação mecânica houve injeção de fluidos diagenéticos em um sistema de fraturas originando veios de quartzo de baixa cristalinidade e enriquecimento de sílica de horizontes silto-arenosos. Uma nova injeção fluidal impulsionada pela ação do magmatismo basáltico acelerou a formação de albitas e deu origem a veios com calcita, quartzo, clorita e pirita. Os dados de d18O e d13C mostram que os carbonatos se precipitaram de um fluido isotopicamente homogêneo sem variações drásticas de temperatura. Valores de d13C entre -8,1 a -4,5 (PDB) indicam uma fonte profunda para o CO2 que deu origem a calcita enquanto que valores de d18O entre +18,9 e +24,1 (SMOW) sugere interações sucessivas do fluido com a rocha hospedeira e abaixamento de temperatura. / Abstract: The Granusso mine is located near the Corderopolis city and constitutes an important source of raw material to the Santa Gertrudes Ceramic Cluster. Late Permian sedimentary rocks of the Corumbataí Formation outcrops in the area. The litological succession comprises a sequence of massif, banded to laminate siltstone topped by carbonate to sandy siltstone. Hydrothermal alteration is an important feature generally associated with host rock whitening. A large basaltic sill intruded the sequence and affected the evolution of the diagenetic and hydrothermal process. Petrographic, chemical and XRD dates suggest that after the mechanical compaction a fluid injection caused the precipitation of low-cristalinity quartz and silica enrichment of sandy-siltstone horizons. A new fluid injection driven by the Serra Geral magmatism triggered albite formation and gave rise to the pyrite-chlorite-quartzcalcite veins. Carbon and oxygen isotope studies of the host rocks and veins show that carbonate precipitated from a homogeneous fluid without strong changes in temperatures along hydrothermal conducts. d13C values of -4,5 to -8,1 (PDB) indicate a CO2 deep-source while d18O of +18,4 to +24,1 (SMOW) and the positive correlarion beetween d18O and d13C values suggest a temperature-dependent trend accompanied by a progressively increasing of fluid/rock interaction. / Doutor

Imaging spectrometry data or hyperspectral imagery acquired using airborne systems have been used in the geologic community since the early 1980&rsquo / s and represent a mature technology. The solar spectral range 0.4&ndash / 2.5 &amp / #956 / m provides abundant information about hydroxyl-bearing minerals, sulfates and carbonates common to many geologic units and hydrothermal alteration assemblages. Satellite based Hyperion image data is used to implement and test hyperspectral processing techniques to identify alteration minerals and associate the results with the geological setting. Sisorta gold prospect is characterized by porphyry related epithermal and mesothermal alteration zones that are mapped through field studies. Image specific corrections are applied to obtain error free image data. Extensive field mapping and spectroscopic survey are used to identify nine endmembers from the image. Partial unmixing techniques are applied and used to assess the endmembers. Finally the spectral correlation mapper is used to map the endmembers which are kaolinite, dickite, halloysite, illite, montmorillonite and alunite as clay group and hematite, goethite and jarosite as the iron oxide group. The clays and iron oxides are mapped with approximately eighty percent accuracy. The study introduces an image specific algorithm for alteration minerals identification and discusses the outcomes within the geological perspective.

The demand for energy and new oil reservoirs around the world has increased rapidly while oil recovery from depleted reservoirs has become more difficult. Oil production from fractured carbonate reservoirs by water flooding is often inefficient due to the commonly oil-wet nature of matrix rocks. Chemical enhanced oil recovery (EOR) processes such as surfactant-induced wettability alteration and interfacial tension reduction are required to decrease the residual oil saturation in matrix blocks, leading to incremental oil recovery. However, improvement in recovery will depend on the degree of wettability alteration and interfacial tension (IFT) reduction, which in turn are functions of matrix permeability, fracture intensity, temperature, pressure, and fluid properties. The oil recovery from fractured carbonate reservoirs is frequently considered to be dominated by the spontaneous imbibition mechanism which is a combination of viscous, capillary, and gravity forces. The primary purpose of this study is to model wettability alteration in the lab scale for both coreflood and imbibition cell tests using the chemical flooding reservoir simulator. The experimental recovery data for fractured carbonate rocks with different petrophysical properties were history-matched with UTCHEM, The University of Texas in-house compositional chemical flooding simulator, using a highly heterogeneous permeability distribution. Extensive simulation work demonstrates the validity and ranges of applicability of upscaled procedures, and also indicates the importance of viscous and capillary forces in larger fields. The results of this work will be useful for designing field-scale chemical EOR processes. / text

The effect of brine ionic composition on oil recovery was studied for a limestone reservoir rock at a high temperature. Contact angle, imbibition, core flood and ion analysis were used to find the brines that improve oil recovery and the associated mechanisms. Contact angle experiments showed that modified seawater containing Mg[superscript 2+] and SO4[superscript 2-] and diluted seawater change aged oil-wet calcite plates to more water-wet conditions. Seawater with Ca[superscript 2+], but without Mg[superscript 2+] or SO₄[superscript 2-] was unsuccessful in changing calcite wettability. Modified seawater containing Mg[superscript 2+] and SO₄[superscript 2-], and diluted seawater spontaneously imbibe into the originally oil-wet limestone cores. Modified seawater containing extra SO₄[superscript 2-] and diluted seawater improve oil recovery from 40% OOIP (for formation brine waterflood) to about 80% OOIP in both secondary and tertiary modes. The residual oil saturation to modified brine injection is approximately 20%. Multi ion exchange and mineral dissolution are responsible for desorption of organic acid groups which lead to more water-wet conditions. Further research is needed for scale-up of these mechanisms from cores to reservoirs. / text