Thesis (M.E.S.)--Evergreen State College, 2008. / "June, 2008." Title from title screen (viewed 4/8/2010). Includes bibliographical references.

No description available.

Lead isotope compositions have been obtained from five major volcanic and intrusive rock suites and several ore deposits on Vancouver Island. Lead, uranium and thorium concentrations and strontium isotope ratios have been obtained for a subset of these samples. The rock suites examined are the Paleozoic Sicker Group, Triassic Karmutsen Formation, Jurassic Island Intrusions and Bonanza Group volcanic rocks, and the Eocene Catface intrusions. Isotope geochemistry of the Sicker Group is consistent with the interpretation that it formed as an island arc. Relatively high 207pb/204pb ratios indicate sediment involvement in the subduction process, which suggests that the Sicker Group formed close to a continent. Buttle Lake ore deposits display decreasingly radiogenic lead isotope ratios with time, suggesting that the associated magmas become increasingly primitive. This supports the hypothesis that these deposits formed during the establishment of rifting in a back-arc environment. Karmutsen Formation flood basalts display isotopic mixing between an ocean island-type mantle source and average crust. Isotopic evidence is used to support a Northern Hemisphere origin for these basalts. Mixing is apparent in the lead and strontium isotope signatures of the Island Intrusions and Bonanza Group volcanic rocks, between depleted mantle and crustal (possibly trench sediments) components. This is consistent with formation of these rocks in an island arc environment. Eocene Catface intrusions have relatively high 207pb/204pb indicating that crustal material was involved in their formation. There are two groups of plutons corresponding to an east belt and west belt classification. Galena from the Zeballos mining camp related to the Eocene Zeballos pluton indicates that the mineralization was derived from the pluton. Galena lead isotope data from Vancouver Island may be interpreted in a general way by comparison with data from deposits elsewhere of known age and origin. No single growth curve model can be applied. Lead isotope characteristics of Vancouver Island are clearly different from those of the North American craton, reflecting the oceanic affinities of this terrane. A new technique has been developed to compare 207pb/204pb ratios between samples with differing 206pb/204pb ratios. The procedure projects 207pb/204pb ratios along suitable isochrons until they intersect a reference value of 206pb/204pb. This technique can be used for interpreting lead isotope data from old terranes, in which lead and uranium may have undergone loss or gain, and if lead and uranium abundances have not been measured. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The central Pelly Mountains in southeastern Yukon Territory consist of imbricate thrust sheets, which have undergone syn- and post-thrusting deformation and metamorphism. The local geology is further complicated by intrusion of Upper Cretaceous batholiths, and by strike-slip faulting related to the Tintina Fault, a major northwest-trending transcurrent fault of uppermost Cretaceous or early Tertiary age. This faulting disrupts the northeast edge of the study area. Upper Devonian and Mississippian strata are present in at least two of the thrust sheets, but the Mississippian volcanic rocks occur in only one of them. The volcanic rocks consist of volcaniclastic material with minor interbedded flows, and were deposited in a submarine environment. Several coeval and cogenetic syenite and trachyte domes and small stocks are the remains of vent areas. Although the volcanic rocks are all highly altered and show evidence of widespread chemical mobility, trace element data indicate that the rocks are meta-luminous trachytes, most closely resembling peralkaline volcanics generated in extensional environments. This suggestion of a predominantly extensional tectonic setting in mid-Mississippian time in the Pelly Mountains is consistent with recent tectonic syntheses for the area. Stratabound and stratiform massive base metal sulphide deposits that occur within the Mississippian volcanic sequence are similar in many respects to the Kuroko-type volcanogenic massive sulphide deposits of Japan. The Pelly Mountains deposits, however, are among the first known occurrences in the world of Kuroko-type mineralization in a rift environment. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Im Rahmen von UPNS4D+ wird von mir der Teilbereich der automatisierten untertägigen Detektion von Gangerzlagerstätten und seltenen Erden bearbeitet. Dies erfolgt mittels eines Multisensoransatzes, der aus einer Hyperspektralkamera, einer RGB-Kamera und einem Laserscanner besteht. Die Grundlagen für die Kombination von hyperspektraler Bildverarbeitung und einer RGB-Kamera sind in der Industrie im Bereich von automatisierten Sortieranlagen zu finden. Im Bereich der Fernerkundung ist der Einsatz hyperspektraler Bilder für die Detektion geologischer Merkmale seit einigen Jahrzehnten üblich. Hier kann im Rahmen meiner Forschung gezeigt werden, dass mittels hyperspektraler Bilder Pyrit unter Tage detektiert werden kann. / In my research I work on a system which detects automatically the ore and rare earth element in a mine. This is part of UPNS4D+. For the detection I use a multi sensor system which consists of a hyperspectral camera, a RGB camera and a Laser scanner. Basics of this combination can be found in the industry. The combination of a RGB camera and a hyperspectral camera enables an automatic sorting of for example waste materials. Landsat satellites in the 1970 uses spectral information in order to detect the geology of the surface. I have tested the hyperspectral imaging in the Reiche Zeche and I can now show that Pyrite can be detected.

Many geologic processes occur in association with hydrothermal fluids and some of these fluids are eventually trapped as fluid inclusions in minerals formed during the process. Fluid inclusions provide valuable information on the pressure, temperature and fluid composition (PTX) of the environment of formation, hence understanding PTX properties of the fluid inclusions is required. The most important step of a fluid inclusion study is the identification of Fluid Inclusion Assemblages (FIA) that represent the finest (shortest time duration) geologic event that can be constrained using fluid inclusions. Homogenization temperature data obtained from fluid inclusions is often used to reconstruct temperature history of a geologic event. The precision with which fluid inclusions constrain the temperatures of geologic events depends on the precision with which the temperature of a fluid inclusion assemblage can be determined. Synthetic fluid inclusions trapped in the one-fluid-phase field are formed at a known and relatively constant temperature. However, microthermometry of synthetic fluid inclusions often reveals Th variations of about ± 1- 4 degrees Centigrade, or one order of magnitude larger than the precision of the measurement for an individual inclusion. The same range in Th was observed in well-constrained natural FIAs where the inclusions are assumed to have been trapped at the same time. The observed small variations are the result of the effect of the fluid inclusion size on the bubble collapsing temperature. As inclusions are heated the vapor bubble is getting smaller until the pressure difference between the pressure of the vapor and the confining pressure reaches a critical value and the bubble collapses. It was observed that smaller inclusions reach critical bubble radius and critical pressure differences at lower temperatures than larger inclusions within the same FIA. Homogenization temperature (Th) variations depend on many factors that vary within different geological environments. In order to determine minimum and acceptable Th ranges fro FIAs formed in different environments we investigated several geologic environments including sedimentary, metamorphic, and magmatic hydrothermal environments. The observed minimum Th ranges range from 1-4 degrees Centigrade and acceptable Th range from 5-25 degrees Centigrade. The variations are mostly caused by the fluid inclusion size, natural temperature and pressure fluctuations during the formation of an FIA and reequilibration after trapping. Fluid inclusions containing H₂O-CO₂-NaCl are common in many geologic environments and knowing the salinity of these inclusions is important to interpret PVTX properties of the fluids. A technique that combines Raman spectroscopy and microthermometry of individual inclusions was developed to determine the salinity of these inclusions. In order to determine the salinity, the pressure and temperature within the inclusion must be known. The pressure within the inclusions is determined using the splitting in the Fermi diad of the Raman spectra of the CO₂ at the clathrate melting temperature. Applying the technique with to synthetic fluid inclusions with known salinity suggests that the technique is valid and useable to determine salinity of H₂O-CO₂-NaCl fluid inclusions with unknown salinity. / Ph. D.

This thesis presents briefly the geology of the Cerro de Pasco district to acquaint the reader with the general geological setting of the district. A study of ore controls for a typical lead-zinc replacement body at the world famous Cerro de Pasco mine in Peru, 102 km northeast of Lima, was undertaken for purposes of better understanding. The particular body selected, the San Alberto Ore Body, occurs as a northeast extension of a main mass of pyrite, known as the "pyrite body", and is enclosed in Triassic- Jurassic limestone. Primary ore controls were determined to be a "Y"-like intersection formed by NS Longitudinal Faulting with a NE striking bedding fault. Resultant brecciation created the necessary permeable conditions whereby ore fluids were channeled away from the pyrite body into the limestone for ore emplacement. Three phases of hydrothermal rock alteration were identified as silicic alteration, chloritic alteration and an outer zone of bleaching and recrystallization. One peculiarity is found in the mineral composition of the silicic alteration, and a hypothesis is presented to explain it. The paragenetic sequence given for hypogene and gangue minerals was determined from the examination of more than 150 thin and polished sections.

No description available.

Les roches vulcanogéniques de la Mine de Seival appartiennent à la Formation Hilário du Bassin de Camaquã, d’âge Néoprotérozoique. Ces roches contiennent six mines inactives avec diverses prospections de cuivre–argent. Les minéralisations semblent associées à un contrôle structurel intense du régime ruptile. La compréhension de la transformation chimique de l’hydrothermalisme associé aux paléo-contraintes est assez faible dans la région. Nous proposons de caractériser la chimie des minéraux des phases magmatiques, tardi–magmatiques et hydrothermales ainsi que de comprendre les contraintes structurales et la géochimie des veines tardives de barytine et calcite. Pour ce faire, nous avons effectué des analyses minéralogiques, et chimiques des phases magmatiques et d’altération. La chimie minérale associée à la modélisation thermodynamique a permis de caractériser l’altération comme tardi– magmatique. L’albitisation (650 à 350 °C) s’est produite en association avec une chloritisation (312 à 120 °C) et avec de la pyrite et de la chalcopyrite. Les températures les plus basses (150 à 50 °C) ont été reliées à la formation de smectite et d’inter-stratifié de chlorite/smectite et avec de la chalcocite–covellite, chalcocite–bornite ou barytine. Nous effectuons les analyses structurales des mesures de cinématique et de la direction des failles/fractures. L’analyse structurale a montré trois contraintes principales survenant dans la Mine Seival et dans le District Minier de Lavras do Sul : compression NW–SW ; compression NE–SW ; distension ENE–SWS. La contrainte NW–SE est la principale direction de contrainte associée à la minéralisation et aux filons minéralisés dans ces deux régions. / The volcanogenic rocks of the Seival Mine belong to Hilário Formation from Camaquã Basin, with ages Neoproterozoic. These rocks contain six inactive mines with various prospects of copper-silver. Mineralization are associated with intense structural control in brittle regime. Chemical transformation of hydrothermal alteration associated with paleostress is not very well understood in the region. We propose a characterization of mineral chemistry of the magmatic phases, tardi–magmatic and hydrothermal as well as understand the paleostress and geochemistry of late veins. For this, we realized analyses of mineral chemistry of magmatic and alteration phase. Mineral chemistry coupled with thermodynamic modeling allowed to characterize the alteration as tardi–magmatic. The albitization (650 to 350 °C) occurred in association with chloritization (312 to 120 °C), and with pyrite and chalcopyrite. The lowest temperatures (150 to 50 °C) were related to formation of smectite and interlayered chlorite/smectite, and with chalcocite–covellite, chalcocite–bornite or barite. We perform structural analyzes through kinematic measures and failure/fracture directions. The analysis on faults, fractures and mineralization showed three main stresses occurring in the Seival Mine and Lavras do Sul Mining District: NW–SE compression; NE–SW compression; ENE–SWS distension. The NW–SE paleostress is the main effort related to the dikes and mineralization in both areas.

The Kalahari Goldridge mine is located within the Archaean Kraaipan Greenstone Belt about 60 km SW of Mafikeng in the Northwestern Province, South Africa. Several gold deposits are located within approximately north - south-striking banded iron-formation (BIF). Current opencast mining operations are focused on the largest of these (D Zone). The orebody is stratabound and hosted primarily in the BIF, which consists of alternating chert and magnetite-chloritestilpnomelane-sulphide-carbonate bands ranging from mm to cm scale. The ore body varies in thickness from 15 to 45 m along a strike length of about 1.5 km. The BlF is sandwiched between a sericite-carbonate-chlorite schist at the immediate footwall and carbonaceous meta-pelites in the hanging-wall. Further west in the footwall, the schists are underlain by mafic meta-volcanic amphibolite. Overlying the hanging-wall carbonaceous metapeiites are schist units and meta-greywackes that become increasingly conglomeratic up the stratigraphy. Stilpnomelane-, chlorite- and minnesotaite-bearing assemblages in the BlFs indicate metamorphic temperatures of 300 - 450°C and pressures of less than 5 kbars. The BIF generally strikes approximately 3400 and dips from 60 to 75°E. Brittle-ductile deformation is evidenced by small-scale isoclinal folds, brecciation, extension fractures and boudinaging of cherty BIF units. Fold axial planes are sub-parallel to the foliation orientation with sub-vertical plunges parallel to prominent rodding and mineral lineation in the footwall. Gold mineralization at the Kalahari Goldridge deposit is associated with two generations of subhorizontal quartz-carbonate veins dips approximately 20 to 40°W. The first generation consists of ladder vein sets (Group lIA) preferentially developed in Fe-rich meso bands, whilst the second generation consists of large quartz-carbonate veins (Group lIB), which crosscut the entire ore body extending into the footwall and hanging-wall in places. Major structures that control the ore body are related to meso-scale isoclinal folds with fold axes subparallel to mineral elongation lineations, which plunge approximately 067°E. These linear structures form orthogonal orientation with the plane of the mineralized shallowdipping veins indicating stretching and development of fluid - focusing conduits. A second-order controlling feature corresponds to the intersection of the mineralized veins and foliation planes of host rock, plunging approximately 008°N and trending 341°. G0ld is closely associated with sulphides, mainly pyrite and pyrrhotite and to a lesser extent with bismuth tellurides, and carbonate gangue. The ore fluid responsible for the gold deposition is in the C-O-H system with increased CH₄ contents attributed to localized hydrolysis reaction between interbedded carbonaceous sediment and ore fluid. The fluid is characterized by significant C0₂ contents and low salinities below 7.0 wt % NaCl equivalent (averages of 3.5 and 3.0 wt % NaCl equivalent for the first and second episodes of the mineralization respectively) . Calculated values of f0₂. ranging from 10⁻²⁹·⁹⁸ to 10⁻³²·⁹⁶ bars, bracket the C0₂-CH₄ and pyrite-pyrrhotite-magnetite buffer boundaries and reveal the reducing nature of the ore fluid at deposition. Calculated total sulphur content in the ore fluid (mΣs), ranges from 0.011 to 0.018M and is consistent with the range (10⁻³·⁵ to 10⁻¹M) reported for subamphibolite facies ore fluids. The close association of sulphides with the Au and nature of the fluid also give credence that the Au was carried in solution by the Au(HS)₂ - complex. Extensive epigenetic replacement of magnetite and chlorite in BIF and other meta-pelitic sediments in the deposit by sulphides and carbonates, both on meso scopic and microscopic scales gives evidence of an interaction by a CO₂- and H₂S-bearing fluid with the Fe-rich host rocks in the deposit. This facilitated Au precipitation due to changes in the physico-chemical conditions of the ore fluid such as a decrease in the mΣs and pH leading to the destabilization of the reduced sulphur complexes. Local gradients in f0₂ may account for gold precipitation in places within carbonaceous sediments. The fineness of the gold grams (1000*Au/(Au + Ag) ranges from 823 to 921. This compares favourably with the fineness reported for some Archaean BIFhosced deposits (851 - 970). Mass balance transfer calculations indicate that major chemical changes associated with the hydrothermal alteration of BIF include enrichment of Au, Ag, Bi, Te, volatiles (S and CO₂), MgO, Ba, K and Rb but significant depletion of SiO₂ and minor losses of Fe₂O₃. In addition, anomalous enrichment of Sc (average, 1247%) suggests its possible use as an exploration tool in the ferruginous sediments in the Kraaipan greenstone terrane. Evidence from light stable isotopes and fluid inclusions suggests that the mineralized veins crystallized from a single homogeneous fluid source during the two episodes of mineralization under the similar physicochemical conditions. Deposition occurred at temperatures rangmg from 350 to 400°C and fluid pressures ranging from 0.7 to 2.0kbars. Stable isotope constraints indicate the following range for the hydrothermal fluid; θ¹⁸H₂O = 6.65 to 10.48%0, 8¹³CΣc = -6.0 to -8.0 %0 and 8³⁴SΣs = + 1.69 to + 4.0%0 . These data do not offer conclusive evidence for the source of fluid associated with the mineralization at the Kalahari Goldridge deposit as they overlap the range prescribed for fluid derived from devolatization of deep-seated volcano-sedimentary piles near the brittle-ductile transition in greenstone belts during prograde metamorphism, and magmatic hydrothermal fluids. / KMBT_363 / Adobe Acrobat 9.54 Paper Capture Plug-in