Micro-geochemistry of the mantle and its volcanic rocks

This thesis comprises three studies which utilise detailed micro-sampling techniques to understand the effects of melt infiltration in the continental lithosphere and the relationship of deeply derived kimberlite melts to lithospheric processes. To be able to make these links it is necessary to better constrain the geochemical composition of the primary kimberlite melt. • The first study investigates inter-grain trace element and Sr isotope variation in clinopyroxene (cpx), amphibole and melt from two spinel lherzolite xenoliths from the Middle Atlas Mountains, Morocco. These results support a multi-stage metasomatic process in which cpx and amphibole are recent additions to the lithospheric mantle, most recently equilibrated with a carbonatite melt. The limited Sr isotope variation in the cpx from this study is typical of global off-craton cpx implying that the majority of cpx in off-craton settings may have a recent, metasomatic origin. • The second micro-sampling study examines inter-grain trace element and Sr isotope variation in garnet and cpx in garnet lherzolite xenoliths within cratonic peridotites from Bultfontein, South Africa, and Pyramidfels, Greenland. The Sr isotope and trace element variation, combined with a lack of trace element equilibrium between cpx and garnet, imply that the majority of cpx is a recent addition, associated with the host kimberlite-type magma, whereas the garnet is added by an older event, probably by a melt related to either Group II kimberlite or lamproite. A global database of Sr and Nd isotope data for cpx and garnet indicates that these conclusions can be applied more widely. The metasomatic addition of cpx and garnet is limited to vein-wallrock reactions and therefore the majority of lithospheric mantle is concluded to be depleted harzburgite or dunite. • The third micro-sampling study focuses on constraining the primary geochemical characteristics of kimberlite magma by analysing the constituent phases (perovskite, olivine, apatite, phlogopite, calcite) for trace element and Sr isotope ratios from a sample of hypabyssal kimberlite from Jos, Somerset Island, Canada. An analogue study was carried out on an olivine melilitite from Saltpetre Kop, South Africa with a similar mineral suite (with the addition of melilite). These results show that phenocrystal olivine and apatite provide the best record of the source Sr isotope composition whereas perovskite, typically analysed by laser ablation, is more variable and influenced by crustal interaction, albeit to a limited extent. The results indicate that previously recorded differences between the Sr isotope compositions of whole rock kimberlites and the low-Cr megacryst suite, used to rule out a genetic relationship between the two, can be ascribed to later stage crustal interaction with the kimberlite. As a result, the link between kimberlites and the formation of the low-Cr megacryst suite is strengthened

The effect of an electrical corona discharge upon the reaction of SO2 to SO3 in low concentration SO2 - air mixtures

An investigation of a pilot plant electrical dust precipitator was conducted to determine its ozone generating characteristics in air as well as the ability of the ozone formed to convert gaseous SO2 to particulate SO3. It was anticipated that in addition to the known primary particulate dust and mist removal function of a precipitator, a secondary gaseous removal facility was inherent in its operation. Ozone formation quantities were determined at varied air flow and electrical power input levels to the precipitator. Maximum ozone generation was 0.02 pounds per hour at an energy input level of 113 KW-HR per pound - approximately one-seventh the efficiency of commercial ozonators. Conversion of gaseous SO2 to particulate SO3 by the ozone generated in the precipitator was determined at varied SO2 concentration levels and air flow rates. Two definite reactions were observed in the formation of SO3 from SO2 by ozone. At SO2 concentrations below 100 P.P.M. five mols of O3 are required per mol of SO3 formed whereas above SO2 concentrations of 400 P.P.M. one mol of ozone produced three mols of SO3. An evaluation of the results obtained indicates that a commercial electrical dust precipitator is an impractical device for reducing gaseous SO2 by reaction of generated ozone to form particulate SO3. While 100% of the generated ozone can convert gaseous SO2 to particulate SO3, the SO2 concentration levels required for the reaction are such that less than 1% of the total SO2 is removed from the gas stream

Sundowners and Mountain Wave Activity: Selected Observations from the Sundowner Winds Experiment (SWEX)

Wildfires in complex terrain have resulted in tragic loss and have highlighted the vulnerability of communities over the past several years. The added intensity created by downslope windstorms, and the lack of high temporal and spatial resolution of ground observations motivates the ongoing need to understand and increase predictability of Sundowners. Sundowners, downslope windstorms that are typically intensified around sunset, are a common and significant weather phenomenon observed along the Santa Barbara coastline and are known to increase challenges during wildfire events. The Sundowner Winds EXperiment (SWEX) was a six-week field campaign from 01 April to 15 May 2022 in Santa Barbara County, California. The campaign utilized ground and air operations to study the dynamics of sundowner winds by increasing spatial and temporal measurements by acquiring thermodynamic and kinematic variables. This thesis focuses on two Intensive Operational Periods (IOP): IOP2 measuring from 5-6 April and IOP6 measuring from 28-29 April. Each period is analyzed using a ground-based LiDAR instrument, radiosondes, dropsondes, and several Integrated Surface Flux System stations. Both events observed strong mountain wave activity and strong surface winds. At the end of the period, observed by several ISFS stations and the LiDAR, there was a rapid onset of weak, southeast winds in response to the onset of the marine boundary layer (MBL). This manuscript focuses on the analysis of observations during sundowner winds, mountain wave activity, and the impact of the MBL

2DV modelling of sediment transport processes over full-scale ripples in regular asymmetric oscillatory flow

Wave-induced, steep vortex ripples are ubiquitous features in shallow coastal seas and it is therefore important to fully understand and model the sediment transport processes that occur over them. To this end, two two-dimensional vertical (2DV) models have been critically tested against detailed velocity and sediment concentration measurements above mobile ripples in regular asymmetric oscillatory flow. The two models are a k–ω turbulence-closure model and a discrete-vortex, particle-tracking (DVPT) model, while the data are obtained in the Aberdeen oscillatory flow tunnel (AOFT). The models and the data demonstrate that the time-dependent velocity and suspended sediment concentration above the ripple are dominated by the generation of lee-side vortices and their subsequent ejection at flow reversal. The DVPT model predicts the positions and strengths of the vortices reasonably well, but tends to overpredict the velocity close to the ripple surface. The k–ω model, on the other hand, underpredicts the height to which the vortices are lifted, but is better able to predict the velocity close to the bed. In terms of the cycle- and ripple-averaged horizontal velocity, both models are able to reproduce the observed offshore flow close to and below the ripple crest and the DVPT model is able to produce the onshore flow higher up. In the vicinity of the vortices, the DVPT model better represents the concentration (because of its better prediction of vorticity). The k–ω model, on the other hand, better represents the concentration close to the ripple surface and higher up in the flow (because of the better representation of the near-bed flow and background turbulence). The measured and predicted cycle- and ripple-averaged suspended sediment concentrations are in reasonable agreement and demonstrate the expected region of exponential decay. The models are able to reproduce the observed offshore cycle- and ripple-averaged suspended sediment flux from the ripple troughs upwards, and as a result, produce net offshore suspended sediment transport rates that are in reasonable agreement. The net measured offshore suspended transport rate, based on the integration of fluxes, was found to be consistent with the total net offshore transport measured in the tunnel as a whole once the onshore transport resulting from ripple migration was taken into account, as would be expected. This demonstrates the importance of models being able to predict ripple-migration rates. However, at present neither of the models is able to do so

The Socio-Legal Impact of Equal Pay Legislation in Ontario, 1946-1979

Equal pay legislation in Ontario has been a source of considerable attention, concern, and conflict since the late nineteenth century. A variety of women\u27s organizations, human rights groups, labour unions, and political parties actively promoted equal pay for equal work legislation. In March 1951, the Ontario provincial government did enact an equal pay law to rectify perceived inequities between male and female workers. Since that initial legislation, numerous individuals and groups have complained that this legislation has done little to narrow the male-female wage differential in Ontario. In this article we argue that, in fact, the Ontario government\u27s equal pay law of 1951 did serve to reduce the male-female wage gap in a variety of jobs over the past thirty years. This contention is seen as providing a positive context for the equal pay for work of equal value legislation recently enacted by Ontario\u27s present Liberal government