Digital Commons Network^™

Arctic Cold Spring Mineralogy As An Indicator Of Spring Deposits, Water, And Habitable Environments On Mars, Melissa M. Battler

Electronic Thesis and Dissertation Repository

Springs exist in many terrestrial settings and have supported microbial communities throughout Earth’s history. There is mounting evidence for spring deposits on Mars from Noachian age to present, implying that water may be circulating in Mars’ subsurface despite current cold, arid conditions. Current datasets for most of Mars are limited to mineralogy via orbital spectroscopy and geomorphology from visual imagery and laser altimetry. Much is known about terrestrial spring morphology, but few springs exist in Mars analogue settings, and of those, few have been investigated for mineralogy. This study reports on two sets of cold spring sites in the Canadian …

Topographic Influences On Trends And Cycles In Nutrient Export From Forested Catchments On The Precambrian Shield, Samson G. Mengistu

Electronic Thesis and Dissertation Repository

This dissertation explored topographic controls on spatial and temporal patterns in water yield and nutrient (carbon, nitrogen and phosphorus) export from forested headwater catchments in the Turkey Lakes Watershed in central Ontario, where other factors contributing to differences in water yield and nutrient export, including climate, geology, forest, and soils, are relatively constant. Topographic characteristics, including (a) hydrological flushing potential (expansion of water table into nitrate-N producing areas); (b) hydrological storage potential (area of wetlands, which can alternatively allow water and nutrients to bypass wetlands when storage capacity is filled with water or to trap them when not filled); and …

Strategies For Visco-Acoustic Waveform Inversion In The Laplace-Fourier Domain, With Application To The Nankai Subduction Zone, Rie Kamei

Electronic Thesis and Dissertation Repository

Waveform inversion is a non-linear and ill-posed inverse problem, with the objective of utilizing the full information content of recorded seismic waveforms. A Laplace-Fourier domain implementation allows a natural `multiscale' approach that mitigates the non-linearity and ill-posedness by inverting low-frequency, early arrival data in the initial stages of inversion. High-frequency components, and late arrivals are incorporated at a later stage. This allows the development of robust inversion strategies capable of handling large wide-angle crustal surveys, leading to reliable, high-resolution velocity and attenuation models of crustal structures. I apply waveform inversion to extract a P-wave velocity model of the active megasplay …

Evaluation Of Jarosite As A Biosignature: A Comparison Of Biogenic And Synthetic Jarosites, Liane Loiselle

Electronic Thesis and Dissertation Repository

The detection of jarosite (K)Fe₃(SO₄)₂OH₆ on Mars has been interpreted as mineralogical evidence of acid-sulfate aqueous processes, including putative evidence of biological activity. Terrestrial habitats where acidic conditions occur are environments where microbiota thrive and generate biological signatures. A biotic and synthetic jarosite were produced to evaluate the ability and effectiveness of existing analytical methods to identify biosignatures in targeted geological materials. Using a comprehensive suite of microscopic (light microscopy, SEM and TEM), mineralogical (XRD), spectroscopic (IR, LIBS, Mössbauer, UV-Vis-NIR, and Raman) and mass spectrometry (ToF-SIMS) techniques, the two jarosites were found to …

Late Archean Oceans: A Laboratory Model Of Oxygen Oases, Maija J. Raudsepp

Electronic Thesis and Dissertation Repository

A cyanobacterial mat, including associated aerobic and anaerobic heterotrophs, was grown in an airtight chamber to simulate the formation of an oxygen oasis in two different Archean-like environments. In the first experiment, methane added to the ecosystem was rapidly oxidized and then O_2(g) increased to 10%. Photosynthesis resulted in a pH of 9.5 and the precipitation of magnesium-manganese carbonates within the mat. In the second experiment, daily additions of ferrous iron were rapidly oxidized, resulting in ferric hydroxide encrusted mat. The growth of cyanobacteria and iron reducing bacteria resulted in an active redox cycle between ferrous and ferric iron. …

Deep Crustal Evolution Of The Western Churchill Province, Nunavut, Canada: Isotopic (U-Pb, O), Trace Element And Micro-Structural Analysis Of Zircon From Lower Crustal Xenoliths, Duane C. Petts

Electronic Thesis and Dissertation Repository

Zircon from lower crustal xenoliths can preserve unique crustal formation records of unexplored levels of the lithosphere. The first such records for the western Churchill province (Nunavut, Canada) are presented here. Zircon SIMS U-Pb geochronology and oxygen isotope analysis were conducted on kimberlite-hosted granulite-facies xenoliths: four metabasites (#9864; #9865; #9866; #9870) from the Rankin Inlet region, and five metabasites (#10162; #10163; #10167; #10169; #10179) and three metatonalite/anorthosites (#10158; #10164; #10168) from the Repulse Bay region. For the Rankin Inlet suite, oscillatory planar zoned, igneous cores from metabolite xenolith #9865 record dates between ca. 2.9–2.6 Ga, whereas complex to radial-sector zoned …

Bacterial Communities And Their Influence On The Formation And Development Of Potholes In Sandstone Surfaces Of The Semi-Arid Colorado Plateau, Kebbi A. Hughes

Electronic Thesis and Dissertation Repository

Potholes are weathering features, of various sizes and shapes, which are found in exposed rock surfaces that lack vegetative and soil cover. Biofilms associated with the ephemeral aquatic pothole environments of the Colorado Plateau were examined as initial and intermediate stages of colonisation of arid, oligotrophic rock surfaces.

Imaging of the interface between pothole biofilms and their host rock revealed features of biological weathering; chiefly, the breakdown of silicate minerals and precipitation of clay and carbonate minerals. High pH measured in pothole water reflected deposition of secondary carbonate minerals at some locations and indicated the development of high pH microenvironments …

Metallogenic Setting Of High-Grade Iron Ores, Mary River District, North Baffin Island, Nunavut, Meghan E. Macleod

Electronic Thesis and Dissertation Repository

Supracrustals of the 2.76-2.71 Ga Mary River Group form the northeastern segment of the Committee Bay Belt. Field mapping has determined that this succession is preserved in structural keels marginal to high-grade gneiss domes and is characterized by lower metasedimentary rocks and an upper BIF-komatiite-quartzite succession. Algoma-type BIF sited at the dome/keel boundary is host to bodies of high-grade iron ore, the largest being Deposit 1 which has an estimated reserve of 500 mt averaging 64 wt % Fe.

Field mapping, petrography, and EMPA indicates 3 main stages of ore formation. Stage 1 was characterized by the formation of the …

An Investigation Of Deformation Structures And Their Tectonic Significance Across The Grenville Front Tectonic Zone In The Vicinity Of Sudbury, Ontario, Canada, Changcheng Li

Electronic Thesis and Dissertation Repository

The Grenville Front Tectonic Zone (GFTZ) is a polyphase deformation belt in the northwest of the Grenville Province which was shaped in the continent-continent-collision-induced Grenvillian Orogeny.

This thesis focuses on the evolution of deformation fabrics in the GFTZ between the Sudbury Basin and French River in Ontario, Canada. Geological mapping using a new digital mapping system was conducted within this segment of the GFTZ, in its northwest vicinity in the Southern Province, and in its southeast vicinity in the Grenville Province. The new digital mapping system includes a personal digital assistant equipped with an internal GPS and a mobile GIS …