The geophysical technique known as Multichannel Analysis of Surface Waves, or MASW (Park et al., 1999) is a relatively new seismic characterisation method which utilises Rayleigh waves propagation. With MASW, the frequency dependent, planar travelling Rayleigh waves are created by a seismic source and then measured by an array of geophone receivers. The recorded data is used to image characteristics of the subsurface. This thesis explains how MASW was used as a geotechnical investigation tool on windfarms in the lower North Island, New Zealand, to determine the stiffness of the subsurface at each wind turbine site. Shear‐wave velocity (VS) profiles at each site were determined through the processing of the MASW data, which were then used to determine physical properties of the underlying, weathered greywacke. The primary research site, the Te Rere Hau Windfarm in the Tararua Ranges of the North Island, is situated within the Esk Head Belt of Torlesse greywacke (Lee & Begg, 2002). Due to the high level of tectonic activity in the area, along with the high rates of weathering, the greywacke material onsite is highly fractured and weathering grades vary significantly, both vertically and laterally. MASW was performed to characterise the physical properties at each turbine site through the weathering profile. The final dataset included 1‐dimensional MASW shear‐wave evaluations from 100 turbine sites. In addition, Poisson’s ratio and density values were characterised through the weathering profile for the weathered greywacke. During the geotechnical foundation design at the Te Rere Hau Windfarm site, a method of converting shear wave velocity profiles was utilised. MASW surveying was used to determine VS profiles with depth, which were converted to elastic modulus profiles, with the input parameters of Poisson’s ratio and density. This study focuses on refining and improving the current method used for calculating elastic modulus values from shear‐wave velocities, primarily by improving the accuracy of the input parameters used in the calculation. Through the analysis of both geotechnical and geophysical data, the significant influence of overburden pressure, or depth, on the shear wave velocity was identified. Through each of the weathering grades, there was a non‐linear increase in shear wave velocity with depth. This highlights the need for overburden pressure conditions to be considered before assigning characteristic shear wave velocity values to different lithologies. Further to the dataset analysis of geotechnical and geophysical information, a multiple variant non‐linear regression analysis was performed on the three variables of shear wave velocity, depth and weathering grade. This produced a predictive equation for determining shear wave velocity within the Esk Head belt ‘greywacke’ when depth and weathering data are known. If the insitu geological conditions are not comparable to that of the windfarm sites in this study, a set of guidelines have been developed, detailing the most efficient and cost effective method of using MASW surveying to calculate the elastic modulus through the depth profile of an investigation site.

In a well-defined subrecess in the Appalachian thrust belt in northwestern Georgia, two distinct regional strike directions intersect at approximately 50°. Fault intersections and interference folds enable tracing of both structural strikes. Around the subrecess, tectonically thickened weak stratigraphic layers—shales of the Cambrian Conasauga Formation—accommodated ductile deformation associated with the folding and faulting of the overlying Cambrian–Ordovician regional competent layer. The structures in the competent layer are analogous to those over ductile duplexes (mushwads) documented along strike to the southwest in Alabama. The intersection and fold interference exemplify a long-standing problem in volume balancing of palinspastic reconstructions of sinuous thrust belts. Cross sections generally are constructed perpendicular to structural strike, parallel to the assumed slip direction. An array of cross sections around a structural bend may be restored and balanced individually; however, restorations perpendicular to strike across intersecting thrust faults yield an imbalance in the along-strike lengths of frontal ramps. The restoration leads to a similar imbalance in the surface area of a stratigraphic horizon, reflecting volume imbalance in three dimensions. The tectonic thickening of the weak-layer shales is evident in palinspastically restored cross sections, which demonstrate as much as 100% increase in volume over the restored-state cross sections. The cause of the surplus shale volume is likely prethrusting deposition of thick shale in a basement graben that was later inverted. The volume balance of the ductile duplex is critical for palinspastic reconstruction of the recess, and for the kinematic history and mechanics of the ductile duplex.

The South Manasan ultramafic intrusion (ca. 1880 Ma) located in the Early Proterozoic Thompson Nickel Belt (TNB) contains Ni and platinum group element (PGE) mineralization hosted by disseminated sulfide. Whole-rock Ni values range from 0.3 to 1.7 wt. % and total precious metals (TPMs) range from 0 to 1.3 ppm Pt + Pd + Au and equate to tenor values (i.e., metal in 100% sulfide) of 11-39 wt. % Ni and 8-27 ppm TPMs. The South Manasan intrusion is a steeply dipping sill-like body with a boudinaged outline having a strike length of approximately 1200 m, average width of 125 m and a minimum depth extent of 1000 m. The intrusion is composed of approximately 25% fresh dunite, 50% serpentine altered dunite and 25% tectonized and carbonate altered dunite. The most intense alteration is found near the intrusion’s margin where it is in contact with metasedimentary rocks of the Pipe Formation, part of the surrounding Ospwagan Group. In fresh dunite the sulfide assemblage characterized by an intercumulate texture is dominated by pentlandite with accessory pyrite; the latter having a symplectic-like texture. The pentlandite-pyrite assemblage in the serpentinized dunite, although still characterized overall by an intercumlate-texture, has well developed platy intergrowths with chlorite and serpentine. In the most intensely modified unit (the carbonate altered dunite) the sulfide assemblage consists primarily of pyrrhotite and pentlandite. Whole-rock geochemical data (n=360), modal mineralogy and mineral chemistry obtained on representative drill core throughout the South Manasan intrusion have been used to establish a type section in order to evaluate the relative roles of primary magmatic versus secondary (i.e., serpentinization, carbonate alteration and deformation) processes. These data indicate that the primary silicate-sulfide assemblage was systematically modified during : serpentinization, carbonate alteration and deformation of the South Manasan intrusion such that a sequence of primary versus secondary events can be established. Intrusion of the original komatiitic magma and formation of the South Manasan intrusion took place at a shallow level into consolidated Ospwagan Group sediments with subsequent contamination of this melt with crustal S. This triggered sulfide saturation and generation of an immiscible sulfide melt. Calculated Ni and TPM tenor values constrain the R factor to between 500 and 2500. The early crystallization of olivine inhibited the sulfide melt from settling to the bottom of the magma column and as a consequence, the sulfides now have a primary interstitial magmatic texture. The current sulfide association dominated by pentlandite>>pyrite>chalcopyrite has a mineral paragenesis that is consistent with subsolidus re-equilibration of a primary pentlanditepyrrhotite- chalcopyrite assemblage. The subsequent processes of serpentinization, deformation and carbonate alteration resulted in modifying the primary sulfide assemblages and their textures (i.e., to platy habits), but did not greatly alter the bulk composition, in particular metal contents, except for addition of volatiles (H2O, CO2). It is concluded therefore that the enrichment of the sulfide assemblage at South Manasan in Ni and PGEs is a consequence of a primary magmatic process involving high R factor and that the effects of later overprinting processes (alteration, deformation) are not responsible for the presently observed high-tenor sulfide association.

In this thesis we examine the generation mechanisms of Pc 5 ULF waves during geomagnetic storms. Also, we study the interaction between Pc 5 ULF waves and energetic particles in the radiation belts and the observed energetic particle flux modulation by Pc 5 ULF waves is verified using particle simulations. Firstly, we present case studies of Pc 5 pulsations using ground-based magnetometer and satellite data during geomagnetic storm times, specifically we selecting three storm time events which show a brief increase in Dst in the main phase of the storms. By studying these events, we attempt to identify the generation mechanisms responsible for the geomagnetic pulsations. The observed pulsations exhibit the characteristic features of a Field Line Resonance. Our results also show evidence for the penetration of ULF wave power in the Pc 5 band to much lower L-shells than normal, suggesting significant reduction of the local Alfven eigenfrequency continuum as compared to non-storm times. This may have considerable significance for the interaction between ULF waves and MeV electrons in the outer radiation belt during storms. Secondly, based on the hypothesis that Pc 5 ULF waves may play an important role in energetic particle dynamics in the radiation belt and ring current, we investigated the relationship between Pc 5 pulsations and energetic particle flux oscillations. We observed very strong Pc 5 oscillations during the great magnetic storm of March 24, 1991 [Lee et al., 2007] and electron flux simultaneously oscillating with the same frequencies in the time domain. We also characterize two more events and present an examination of the relationship between the electron flux modulation and Pc 5 ULF pulsations. Based on our observations, the modulation of energetic particles might be associated with a drift-resonance interaction, or the advection of an energetic particle density gradient. Finally, we numerically calculate the trajectories and energy change of charged particles under the influence of model ULF wave electric fields. This modeling work is used to help to explain the observations and provides evidence which supports the modulation mechanisms such as advection of a flux gradient and drift resonance.

国立情報学研究所で電子化したコンテンツを使用している。

Thesis (M.S.)--Auburn University, 2007. / Abstract. Includes bibliographic references (ℓ. 70-71)

Thesis (Ph. D.)--Macquarie University, Division of Environmental & Life Sciences, Department of Earth and Planetary Sciences, 2005. / Includes bibliographical references (leaves 202-224).

Th.--Archéol. / Bibliogr. p. 235-246.

Thesis (MSc (Geography and Environmental Studies))--University of Stellenbosch, 2005. / 81 Leaves printed on single pages i-xi, preliminary pages and numbered pages 1- 70. Includes bibliography, list of tables and list of figures. / Digitized at 300 dpi color PDF format (OCR), using KODAK i 1220 PLUS scanner. / ENGLISH ABSTRACT: Geological field mapping is often limited by logistical and cost constraints as well as the scope and extent of observations possible using ground-based mapping. Remote sensing offers, among others, the advantages of an increased spectral range for observations and a regional perspective of areas under observation. This study aimed to determine the accuracy of a collection of image classification techniques when applied to ASTER reflectance data. Band rationing, the Crosta Technique, Constrained Energy Minimization, Spectral Correlation Mapping and the Maximum Likelihood Classifier were evaluated for their efficiency in detecting and discriminating between greenstone and granitoid material. The study area was the Archaean Barberton Greenstone Belt in the eastern Mpumalanga Province, South Africa. ASTER reflectance imagery was acquired and pre-processed. Training and reference data was extracted from the image through visual inspection and expert knowledge. The training data was used in conjunction with USGS mineral spectra to train the five classification algorithms using the ERDAS's software package. This resulted in abundance images for the target materials specified by the training data. The Maximum Likelihood Classifier produced a classified thematic map. The reference data was used to perform a rigorous classification accuracy assessment procedure. All abundance images were thresholded to varying levels, obtaining accuracy statistics at every level. In so doing, threshold levels could be defined for every abundance image in such a way that the reliability of the classification was optimized. For each abundance image, as well as for the output map of the Maximum Likelihood Classifier, user's- and producer's accuracies as well as kappa statistics were derived and used as comparative measures of efficiency between the five techniques. This information was also used to assess the spectral separability of the target materials. The Maximum Likelihood Classifier outperformed the other techniques significantly, achieving an overall classification accuracy of 81.1% and an overall kappa value of 0.748. Greenstone rocks were accurately discriminated from granitoid rocks with accuracies between 72.9% and 98.5%, while granitoid rocks showed very poor ability to be accurately distinguished from each other. The main recommendations from this study are that thermal infrared and gamma-ray data be considered, together with better vegetation masking and an investigation into object orientated techniques. / AFRIKAANSE OPSOMMING: Geologiese veldkartering word algemeen beperk deur logistiese en koste-verwante faktore, sowel as die beperkte bestek waartoe waarnemings met veld-gebasseerde tegnieke gemaak kan word. Afstandswaarneming bied, onder andere, 'n vergrote spekrale omvang vir waarnemings en 'n regionale perspektief van die area wat bestudeer word. Hierdie studie was gemik daarop om die akkuraatheid van 'n versameling beeld-klassifikasie tegnieke, toegepas op ASTER data, te bepaal. Bandverhoudings, die Crosta Tegniek, "Constrained Energy Minimization", Spektrale Korrellasie Kartering, en Maksimum Waarskynlikheid Klassifikasie is evalueer op grond van hul vermoë om groensteen en granitoied-rotse op te spoor en tussen hulle te onderskei. Die studiegebied was die Argalese Barberton Groensteengordel in die oostelike Mpumalanga Provinsie in Suid Afrika. 'n ASTER refleksie beeld is verkry, waarop voorverwerking uitgevoer is. Opleidings- en verwysingsdata is van die beeld verkry deur visuele inspeksie en vakkundige kennis. Die opleidingsdata is saam met VSGO mineraalspektra gebruik om die vyf klassifikasie algoritmes met behulp van die ERDAS sagteware pakket op te lei. Die resultaat was volopheidsbeelde vir die teikenmateriale gespesifiseer in die opleidingsdata. Die Maksimum Waarskynlikheid algoritme het 'n geklassifiseerde tematiese beeld gelewer. Met behulp van die verwysingsdata is 'n streng akkuraatheidstoetsing prosedure uitgevoer. Vir alle volopheidsbeelde is 'n reeks drempelwaardes gestel, en by elke drempelwaarde is akkuraatheidsstatistieke afgelei. Op hierdie manier kon 'n drempelwaarde vir elke volopheidsbeeld vasgestel word sodat die drempelwaarde die betroubaarheid van die klassifikasie optimeer. Vir elke volopheidsbeeld, asook vir die tematiese kaart verkry van die Maksimum Waarskynlikheid klassifikasie, is gebruikers- en produsent-akkuraathede en kappa statistieke bereken. Hierdie waardes is gebruik as vergelykende maatstawwe van akkuraatheid tussen die vyf tegnieke, asook van die spektrale skeibaarheid van die onderskeie teikenmateriale. Die Maksimum Waarskynlikheid klassifikasie het die beste resultate gelewer, met 'n algehele klassifikasie akkuraatheid van 81.1%, en 'n gemiddelde kappa waarde van 0.748. Groensteenrotse kon met hoë akkuraathede van tussen 72.9% en 98.5% van granitoiedrotse onderskei word, terwyl granitoiedrotse 'n swak vermoë getoon het om van mekaar onderskei te word. Die belangrikste aanbevelings vanuit hierdie studie is dat termiese uitstralingdata asook gamma-straal data geimplimenteer word. Beter verwydering van plantegroei en 'n studie na die lewensvatbaarheid van objekgeorienteerde metodes word ook aanbeveel.

O significado da idade do magmatismo, reconhecimento das séries magmáticas e ambientes tectônicos que controlaram a origem das rochas metavulcânicas do Greenstone Belt da Vila Nova (GBVN), é uma importante ferramenta para entender a evolução do Escudo das Guianas durante o Paleoproterozóico. Este trabalho apresenta novos dados geoquímicos de rochas metavulcânicas e de U/Pb em zircão (LA-MC-ICPMS), que foram suplementados por petrografia, dados estratigráficos e estruturais obtidos através de mapeamento geológico e descrição de furos de sondagem. Na região de Vila Nova, as unidades do GBVN repousam sobre o embasamento Arqueano composto por ortognaisses, metagranitos e anfibolitos do Complexo Tumucumaque. A base do GBVN é composta por metabasaltos e metabasaltos andesíticos, sotoposto por um domínio superior metassedimentar com rochas químico exalativas e metavulcânicas subordinadas. As rochas metavulcânicas incluem anfibolitos e anfibólio xistos, cujos corpos estão alongados segundo a xistosidade regional de direção NW-SE. A geocronologia pelo método U-Pb em zircão mostra uma idade de 2.154 ± 6 Ma para um meta-andesito da porção inferior do GBVN. O evento de metamorfismo orogênico esteve associado a três eventos deformacionais. Os eventos D1 e D2 formaram a xistosidade (S1), preservada como dobras intrafoliais (F2) e a clivagem de crenulação (S2), originadas a partir de movimentos de cavalgamento. O pico metamórfico (M1) está marcado pela assembleia plagioclásio+hornblenda+granada e, plagioclásio+hornblenda+diopsídio, indicando temperaturas entre 450 e 650 °C e pressão entre 4 e 6 kbares. Os metabasitos compreendem Fe-toleítos e Mg-toleítos com afinidade komatitica, composições geoquímicas enriquecidas em LILE e ETR e empobrecidas em HFSE (com anomalias negativas de Nb, Ti e P) e padrões de ETR semelhantes ao MORB. As características observadas indicam um magmatismo toleítico relacionado à bacias de retro-arco e arco de ilhas de 2.15 Ga no Escudo das Guianas. / The significance of the age of magmatism, magma series and tectonic settings that controls the origin of metavolcanic rocks of Vila Nova Greenstone Belt (VNGB) is an important issue in order to understand the evolution of Guiana Shield in Paleoproterozoic times. This work presents new U-Pb LA-ICP-MS geochronological and geochemical analyzes carried out on zircon grains and metavolcanic rocks of the Vila Nova greenstone belt (VNGB) which were supplemented by petrography, and stratigraphic and structural data acquired through description of boreholes and field work. In the Vila Nova region, the VNGB units rest on the Archaean basement composed of orthogneisses of the Tumucumaque Complex. The lower portion of the VNGB is composed of metabasalts and andesitic metabasalts, supported by an upper metasedimentary domain with exhalative chemical rocks and subordinate metavolcanic rocks. The metavolcanic rocks include amphibolites and amphibole schists, whose bodies are elongated according to the regional NW-SE schistosity. U-Pb zircon geochronology data showed an age of 2154 ±6 Ma for a meta-andesite of the lower portion of VNGB. Orogenic metamorphism event followed by three deformation events were recognized. The D1 and D2 events formed the schistosity (S1), preserved as intrafolial folds (F2) and the crenulation cleavage (S2), derived from thrust movements. The assemblages plagioclase + hornblende + garnet and plagioclase + hornblende + diopside define the metamorphic peak (M1-M2) with temperatures from 450-650 °C and lithostatic pressure between 4 and 6 kbars. The metabasites comprise Fe-tholeiites and Mg-tholeiites with komatiitic affinity, geochemical compositions enriched in LILE and REE and depleted in HFSE (with negative Nb, Ti and P anomalies) and MORB-like REE patterns. The observed features indicate an expressive magmatism related to back-arc basins and island arcs at 2.15 Ga in Guiana Shield.