Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 171-186). Also available on the World Wide Web.

Approximately 150 meters (500 feet) of Grande Ronde Basalt and 140 meters (450 feet) of Wanapum Basalt of the Columbia River Basalt Group are exposed in the Bull Run Watershed. In Bull Run, the Grande Ronde Basalt is divided into three mappable units: "low Mg" R2 (at least one flow), "low Mg" N2 (approximately four flows), and "high Mg" N2 (two to three flows}. The Wanapum Basalt is represented by two members: Frenchman Springs Member (six flows) and Priest Rapids Member (one flow). These units are identified by instrumental neutron activation analysis, paleomagnetism based on measurements with a fluxgate magnetometer, petrography, lithology, jointing, and stratigraphic position.

Studies of the evolution of hotspot swells, mantle plumes, and Hawaiian basalts are presented in three parts in this dissertation. In part 1, the evolution of mid-plate hotspot swells are simulated numerically as an oceanic plate rides over a hot, upwelling mantle plume. The transient heat transfer equations, with time- and space-dependent boundary conditions, are solved in cylindrical coordinates. Geophysical data are used to constrain the models. Formation of the Hawaiian swell requires a mechanism of convective thinning of the lithosphere. The models constrain the Hawaiian heat source to have a maximum anomalous temperature of 250-300°C, and a perturbing heat flux 5-6 times the background value. On the other hand, the Bermuda swell is likely produced by heat conduction due to weakness of the heat source. In part 2, an analytic model of axisymmetric mantle plumes is presented. Plume parameters beneath the lithosphere, which are constrained from the swell models, are used to infer the plume source regions. The Hawaiian plume likely originates near the core-mantle boundary, but other hotspots may have shallower sources. Chemical plumes are much narrower than thermal plumes because of low chemical diffusivity in the mantle. For mantle plumes driven by combined thermal-chemical diffusion, the chemical signature of the source regions may only be observed near plume centers. Finally, melt generation and extraction along the Hawaiian volcanic chain are discussed in part 3. As a part of the plate moves over the heat source, melting largely takes place in the region where the lithospheric material is engulfed and swept away by the flow of the heat source. At least three mantle components must be involved in the melt generation: the plume material, the asthenosphere, and the engulfed lithospheric material. Significant amount of melts may also come from direct melting of the upwelling plume at depths below the initial plate-plume boundary. Melt extracts continuously from an active partial melting zone of 10-20 km thick, which moves outward as heating and compaction proceed. The models explain quantitatively the general characteristics of Hawaiian volcanism as the result of plume-plate interaction.

Columnar jointing is a fracture pattern, best known from locations such as the Giant's Causeway, or Fingal's Cave, in which cracks self-organize into a nearly hexagonal arrangement, leaving behind an ordered colonnade. In this thesis observations of columnar jointing are reported from both a controlled laboratory setting, and in cooled lava flows. Experiments were performed in slurries of corn starch and water, which form columnar joints when dried. This drying process is examined in detail, and it is shown how desiccation leads to the propagation of a sharp shrinkage front. In general, but with some significant exceptions, the size of columnar joints is inversely dependent on the speed of this shrinkage front during their formation. The exceptions, which include sudden jumps in column scale, show that hysteresis is also important in choosing the column scale. Novel observations of the 3D structure of joints in starch show that columnar joints do not settle down to a perfect hexagonal pattern, but rather mature into a continuously evolving dynamic pattern. This pattern is scale invariant, and the same statistical distribution of column shapes applies equally to joints in both starch and lava. Field work was performed to study columnar jointing in the basalts of the Columbia River Basalt Group and the island of Staffa, and the more heterogeneous lava flows of Southwestern British Columbia. The widths of columns and the heights of striae (chisel-like markings that record details of cooling) were examined in detail, and these length scales are shown to be inversely proportional to each other. An additional length scale, that of wavy columns, is also first reported here. Based on these measurements, empirical advective-diffusive models are developed to describe the transport of water in a drying starch-cake, and the transport of heat in a cooling lava flow. These models have only a single scaling parameter, the Péclet number, which relates the fracture front velocity times the column size to the (thermal or hydraulic) diffusivity. In both cases, the formation of columnar joints occurs at a Péclet number of about 0.2. This model explains the hundred-fold differences in scale between columnar joints in starches and lavas, and can be used as a tool for the interpretation of joint patterns in the field.

Tradicionalmente, os estudos que tinham a exploração pecuária como foco, se limitavam a análise de seus indicadores produtivos e econômicos, ou seja, dava-se um enfoque parcial, setorial ou disciplinar. Igualmente, de um ponto de vista estático e baixo equilíbrio. Por sua vez, a exploração pecuária é um sistema aberto, submetido à influência de um entorno que denominamos ambiente, e que, gerido pelo pecuarista, persegue determinadas finalidades. Por conseqüência, a exploração pecuária é sensível a um amplo leque de fatores de natureza biofísica, sociológica, econômica e de políticas. Neste sentido, as explorações pecuárias como sistemas sociais, são dinâmicas, reativas ou evolutivas, o que significa que as características mais importantes aparecem ao longo do tempo. Por isso, o estudo dos sistemas pecuários requer a consideração explícita da dita variável, tempo. O presente estudo pretende dar resposta a seguinte questão: que mudanças aconteceram nas explorações pecuárias da região de Basalto como reação aos condicionantes do entorno socioeconômico, em constante mudança, mas também, dependentes de fatores e características internas a própria exploração? A região de Basalto, a mais extensa do Uruguai, correspondente a 21% do território nacional, é caracterizada fundamentalmente por estar associada a sistemas extensivos de produção pecuária de baixa produtividade e investimento, onde pastoreiam conjuntamente, bovinos e ovinos. A abordagem metodológica utilizada neste estudo baseou-se na comparação do processamento de informações correspondentes aos anos 1994 e 2008, utilizando como ferramenta, entrevistas dirigidas as mesmas explorações pecuárias da região de Basalto com áreas superiores a 200 hectares. O reconhecimento das mudanças ocorridas nos sistemas pecuários da região de Basalto, no marco das transformações recentes do setor agropecuário do Uruguai, é fundamental para explorar evoluções distintas da pecuária extensiva daquela região, apesar da incerteza a respeito das políticas agrárias dos condicionantes socioeconômicos. Os resultados encontrados sugerem a existência de fatores que ameaçam a continuidade das explorações pecuárias em longo prazo e, conseqüentemente, a sustentabilidade dos ecossistemas pastoris. Estes fatores são de natureza diversa: ambientais econômicos e sociais. / Traditionally, the livestock production studies limited the analysis to productive and economic results, which is to say from a partial approach, or from only one discipline. Also, they were done from a static point of view and supposing a situation at equilibrium. However, the livestock farm is an open system, exposed the influence of its environment, and managed by livestock farmers who have certain purposes. Consequently, the cattle operation is sensible to an ample variety of factors of biophysical, sociological, economic, and ecological nature and also to policies. In this sense, the cattle operations like social systems are dynamic, reactive or adaptive, which means that the most important characteristics appear on the long time. For this reason, the study of the cattle systems requires the explicit consideration this variable, time. The present study tries to give answer to the following question: What changes arose in the cattle operations of the Basalt reacting to the conditions of the socio-economic environment in constant change, but also depending on the own operation internal factors and characteristics? The Region of the Basalt, the most extensive of Uruguay, 21% of the national territory, has been characterized essentially as having extensive systems of cattle production of low productivity and investment; where bovine and ovine graze simultaneously. The methodological approach in this study is based on the comparison of information corresponding to years 1994 and 2008, from the same sample of farms - of the Region of the Basalt with surfaces majors to the 200 hectares -. The data of the changes occurred in the cattle systems of the Basalt Region within the framework of the recent transformations of the farming sector of Uruguay, is fundamental to explore extensive cattle ranch different evolutions, in presence of the uncertainty with respect to the agrarian policies and to the socio-economic conditions. The results suggest the existence of factors that threaten the continuity of the cattle operations in the long term, and therefore, the sustainability of the pastoral ecosystems. These factors are of diverse nature: environmental, economic and social.

Master of Science / Department of Geology / Matthew Brueseke / It is generally accepted that beneath flood basalt provinces, Cu-Ni-PGE sulfide deposits may be found (Ridley, 2013). The focus of this study is the Steens Basalt, a mid-Miocene flood basalt from the northern Great Basin (USA) which contains between ~5-400 ppm copper and is characterized by large plagioclase phenocrysts, some of which can contain primary inclusions of copper despite the chalcophile nature of Cu (Hofmeister and Rossman, 1985; Johnston et al., 1991). The purpose of this project is to identify the distribution of Cu among coexisting phases in Steens Basalt, test whether plagioclase crystals in Steens lavas can host Cu, even when Cu is not visible, and test whether sulfide minerals/droplets are present in Steens Basalt samples with low Cu concentrations. Samples of Steens lavas were examined for sulfide minerals via reflected light microscopy, Raman spectroscopy, and X-ray diffraction with a molybdenum tube. Using an electron microprobe, silicate minerals, oxides, glass, and sulfides were analyzed for their Cu concentration, as well as other major and trace element chemistry. Glass did not contain detectable Cu which precluded partition coefficient (Kd) calculations. Based on average Cu concentration for the non-sulfides, magnetite contains the most Cu, followed by (forsteritic) weathered olivine, pyroxene, olivine, plagioclase, and ilmenite. Copper sulfides were discovered in samples MB97-19 and MB97-76C with additional non-copper sulfides in MB97-76B. In conclusion, these results lay the groundwork for further investigation into potential copper sulfide reserves in the magma plumbing as with other flood basalt packages linked to economically important mineral deposits.

Exposed weathering profiles of a series of Pololu lava flows in Kohala, Hawaii are ideal for investigating the sequence of reactions/reaction pathways of weathered basalt. Weathering reactions for saprolites show mineral sequences that include feldspar → halloysite ± gibbsite + solutes; clinopyroxene → hematite + minor halloysite + solutes; olivine → hematite + solutes; magnetite → hematite or other Fe-oxides/hydroxides. However, the presence of smectite in four samples suggests that smectite-group clays may form as short lived intermediates at the base of the weathering profile. Regionally, on Kohala, soils and saprolites are dominated by halloysite with small quantities of other clays such as kaolinite, gibbsite, and smectite. However, one horizon in the weathering profile at the study site in Kohala is dominated by gibbsite. Smectite is found at the base of the profile above impermeable areas where mass leaching has left increased alkaline and alkaline earth elemental (Mg, Ca, Na, and K) abundances relative to the parent rock. The amount of elemental gain varies from -5% to +75% for samples with smectite. Different climates generate different weathering profile depths. MASW (multi-channel analysis of surface waves) shows that the depth of the weathering profile is 15 meters. Seismic profiles correlate the depth of the weathering profile inland (~15 meters), with cliff face (~13 meters). Other than the gibbsite horizon, most mineral zones are too thin to be resolved through second-order velocity variations. P-wave reflection surveys are unsuitable for imaging the base of the weathering front because the transition to fresh rock may be gradational. However, within the saprolite section, boundaries between relict lava flow textures produce reflections that mimic expected stratigraphic patterns. Perpendicular to the shoreline, reflectors dip gently seaward, whereas parallel to the shoreline, lenticular packages of relict lava flows are observed.

No description available.

Geotechnical investigations undertaken by GHD Pty Ltd uncovered a previously undescribed rock type in the suburbs of Footscray and Alphington approximately 5 km west and 6.5 km east of Melbourne CBD respectively. The rock encountered appeared to be a breccia type rock with angular high strength fine gravel to boulder sized fragments of relatively unweathered grey to dark grey basalt surrounded by a matrix of orangish brown fine grained brittle material resembling hard clay. Pillow basalts were also encountered in the deposits in the form of 0.6 m or larger globular but highly fractured basalt bodies within the rock mass. The rock was eventually identified as a hyaloclastite, a rock type formed when basalt lava flows into water bodies and is quench fragmented. The debris forms piles of basalt and volcanic glass fragments. The volcanic glass fragments are thermodynamically unstable and are altered to palagonite within as little as 20 years from initial deposition. No prior reference to the occurrence of hyaloclastite in the Melbourne region could be found. As such, the location, extent and geotechnical properties of this rock type are unknown, posing a potential risk to infrastructure and construction projects. This study aimed to investigate the possible origins of the hyaloclastite; develop a theory of emplacement/origin; identify other locations where this rock type may exist; determine the geotechnical properties and engineering geological behaviour of the rock; and develop a classification system for the rocks encountered. A variety of methods were used to gather sufficient information to allow the occurrences and geological and geotechnical nature of hyaloclastites and pillow basalts in the Melbourne area to be better understood. Samples of the rock were obtained during the geotechnical investigations undertaken in Footscray and Alphington and outcrop mapping was completed on exposures identified during the course of this study. Historical borehole logs and as built drawings were obtained to assist in the understanding of the previous description terminology associated with the rock now identified as hyaloclastite. Standard and “non-standard” laboratory testing was undertaken as well as classification testing. The field of block-in-matrix rocks “bimrocks” was assessed as a possible method to assist in the understanding of the behaviour and geotechnical properties of the hyaloclastite rock with or without pillow basalts. The RMR, Q-System and GSI rock mass classification systems were used to help understand the rockmass characteristics. A weak rock classification system, a weathered rock characterisation system and a ground behaviour characterisation system were also used to provide information on the possible behaviour of the hyaloclastite type rocks. Development of both 2D and 3D geological models of the two sites indicate that the hyaloclastites encountered in Melbourne were deposited in “lava-deltas”. The hyaloclastites were deposited on advancing subaqueous delta fronts with an overlying layer of subaerial basalt above what has been termed the “passage zone” which represents the historical level of water into which the lava flowed. Strength testing undertaken on the various samples suggested that the hyaloclastite should be classified as a weak rock, with UCS values of ranging from approximately 1 MPa to 10 MPa, and a median UCS value of 1.37 MPa. Using the compiled UCS data and PLT data an estimate of the PLT Is50 to UCS conversion factor “k” was calculated as 10.4. The results of jar slake testing and weatherability index testing were variable: whilst the majority of samples showed no sign of slaking, one sample showed a strong reaction. The samples of disaggregated rock were classified as sandy gravel as per AS1726:1995. Whilst the fine to medium gravel was of subangular grains of basalt the sand was found to be made up of angular fragments of palagonite. Plasticity index and XRD testing of fines obtained from the disaggregation process indicated that the fines are comprised of illite and smectite clay minerals and behave as a high plasticity silt. Several categorisation methods utilised indicated that the hyaloclastite type rockmass strength parameters are controlled partly by the strength of the matrix and partly by the discontinuities and that the rock mass strength is dominated by the pillow basalt behaviour (typical hard rock type behaviours) only once the content of these structures in these rocks exceeds a volume content of 75% pillows to 25% hyaloclastite. Rock mass strength and deformation calculations indicate that the hyaloclastite rock mass is both very weak and also highly deformable (rock mass modulus <100 MPa) when compared with the highly weathered subaerial basalt (~500 MPa) and the fresh/slightly weathered basalt (~15000 MPa). A value of petrographic constant mi used in the Generalised Hoek Brown Criterion was also determined to be 7.01. This is considerably different to the values suggested for “breccia” in the literature of 19±8. A modulus ratio of 150 was also estimated using testing data from Melbourne and also Iceland. The extent of hyaloclastite in the Melbourne region remains unknown. Whilst the location of these deposits is associated with the base of palaeovalleys now infilled by volcanic products, hyaloclastite does not occur in the base of all the palaeovalleys and is expected to be controlled by sea level change and also disruption of drainage lines by damming caused by earlier subaerial flows. Geotechnical practitioners must be aware of the potential occurrence of hyaloclastite as both the hyaloclastite and hyaloclastites with pillow basalt rock masses were found to be significantly weaker and more deformable than the highly weathered subaerial basalt rock. Misidentification of the rock as highly weathered basalt during geotechnical investigation may result in significant under-design. In addition, rock mass behaviour categorisation indicates that block-falls of pillow basalt from excavation walls and roofs may be a risk. Increased excavation effort to remove the pillow basalt structures should also be factored in to projects. To aid identification and understanding of the potential hazards associated with hyaloclastite type rocks, a series of reference sheets has been developed. These reference sheets aim to increase practitioners’ knowledge of hyaloclastites, and the implications for excavation and construction. The reference sheets also provide geomechanical details. Three-dimensional simplified engineering geological block models have also been included to provide graphical information on the relationships and possible geohazards of the various rock types. Future research should aim to further define the extent and engineering properties of hyaloclastites in the Melbourne region and to further define the petrographic constant mi, a better estimate of modulus ratio based on instrumented UCS tests. It is also hoped that now this rock has been recognised in Melbourne that the geotechnical community will reassess previous projects and start to build knowledge on the whereabouts of hyaloclastite and pillow basalt type rocks in the Melbourne area.

Missions to Mars aim to characterize rock and subsurface soil samples and possibly bring some back to Earth for more thorough and sophisticated examination. The Martian surface is covered with basalt which has high compressive strength (andamp;gt;130 MPa), and is more difficult to drill than the much softer sedimentary formations that are presently being drilled using diamond core drills. The main objective of this thesis work is to provide the requisite groundwork towards the development of improved and sustainable drills for subsurface drilling applications on Mars, when their goals are obtaining samples. Since progressive drill-wear is substantial in sustained drilling, the experiments were designed and conducted to study the tool-wear mechanisms and understand the associated effects on drilling performance in subsurface drilling of basalt. Core drilling experiments are conducted with different drill geometries and cutting conditions in a Martian simulant, basaltic rock; monitoring thrust force, torque and measuring tool-wear for a series of successive depth-increments. Based on the experimental results an optimization model has been developed for maximizing drilling depth with minimum tool-wear. This preliminary work will help the development of smart and sustainable drills for dry drilling applications for future NASA missions to Mars.