Mémoire (M.Sc.T.)--Université du Québec à Chicoutimi, 1989. / Document électronique également accessible en format PDF. CaQCU

Mémoire (M.Sc.A.)--Université du Québec à Chicoutimi, 1990. / Tableau de correlation en pochette. "Mémoire présenté en vue de l'obtention du grade de Maître es Sciences appliquées (M.Sc.A.)" CaQCU CaQCU Document électronique également accessible en format PDF. CaQCU

Mémoire (M.Sc.A.))--Université du Québec à Chicoutimi, 1989. / Document électronique également accessible en format PDF. CaQCU

Thèse (D.R.M.)--Université du Québec à Chicoutimi, 1997. / Document électronique également accessible en format PDF. CaQCU

Mémoire (M.Sc.T.)--Université du Québec à Chicoutimi, 2000. / Document électronique également accessible en format PDF. CaQCU

Thèse (M.Sc.T.) -- Université du Québec à Chicoutimi, 2006. / Bibliogr.: f. 174-181. Document électronique également accessible en format PDF. CaQCU

Thesis (Ph. D.)--Pennsylvania State University, 1990. / Vita. Includes bibliographical references.

abstract: Chemical and mineralogical data from Mars shows that the surface has been chemically weathered on local to regional scales. Chemical trends and the types of chemical weathering products present on the surface and their abundances can elucidate information about past aqueous processes. Thermal-infrared (TIR) data and their respective models are essential for interpreting Martian mineralogy and geologic history. However, previous studies have shown that chemical weathering and the precipitation of fine-grained secondary silicates can adversely affect the accuracy of TIR spectral models. Furthermore, spectral libraries used to identify minerals on the Martian surface lack some important weathering products, including poorly-crystalline aluminosilicates like allophane, thus eliminating their identification in TIR spectral models. It is essential to accurately interpret TIR spectral data from chemically weathered surfaces to understand the evolution of aqueous processes on Mars. Laboratory experiments were performed to improve interpretations of TIR data from weathered surfaces. To test the accuracy of deriving chemistry of weathered rocks from TIR spectroscopy, chemistry was derived from TIR models of weathered basalts from Baynton, Australia and compared to actual weathering rind chemistry. To determine how specific secondary silicates affect the TIR spectroscopy of weathered basalts, mixtures of basaltic minerals and small amounts of secondary silicates were modeled. Poorly-crystalline aluminosilicates were synthesized and their TIR spectra were added to spectral libraries. Regional Thermal Emission Spectrometer (TES) data were modeled using libraries containing these poorly-crystalline aluminosilicates to test for their presence on the Mars. Chemistry derived from models of weathered Baynton basalts is not accurate, but broad chemical weathering trends can be interpreted from the data. TIR models of mineral mixtures show that small amounts of crystalline and amorphous silicate weathering products (2.5-5 wt.%) can be detected in TIR models and can adversely affect modeled plagioclase abundances. Poorly-crystalline aluminosilicates are identified in Northern Acidalia, Solis Planum, and Meridiani. Previous studies have suggested that acid sulfate weathering was the dominant surface alteration process for the past 3.5 billion years; however, the identification of allophane indicates that alteration at near-neutral pH occurred on regional scales and that acid sulfate weathering is not the only weathering process on Mars. / Dissertation/Thesis / Ph.D. Geological Sciences 2011

Feedbacks between climate, tectonics and erosion drive mineral dissolution in the subsurface and may provide strong controls on chemical weathering as a mechanism for modulating climate through CO2 drawdown. However, few quantitative evaluations of chemical weathering intensity or flux variations with time exist to support this hypothesized feedback. Trace element concentrations in colluvial sediment demonstrate that in unglaciated mid-latitude terrain, climate exerts a strong control on chemical weathering intensity and erosion over glacial-interglacial cycles by modulating the efficacy of abiotic and biotic processes. Weakly chemically altered sediment corresponds with high erosion rates during the Last Glacial interval (vice versa during the Holocene) such that we observe stable weathering rates despite variations in temperature and vegetation. Our results suggest that climate-weathering feedbacks in mid-latitude regions may be weaker than previously hypothesized and provide a new framework to explain stable solute fluxes over Milankovitch climate fluctuations. / 10000-01-01

abstract: Chemical and physical interactions of flowing ice and rock have inexorably shaped planetary surfaces. Weathering in glacial environments is a significant link in biogeochemical cycles – carbon and strontium – on Earth, and may have once played an important role in altering Mars’ surface. Despite growing recognition of the importance of low-temperature chemical weathering, these processes are still not well understood. Debris-coated glaciers are also present on Mars, emphasizing the need to study ice-related processes in the evolution of planetary surfaces. During Earth’s history, subglacial environments are thought to have sheltered communities of microorganisms from extreme climate variations. On Amazonian Mars, glaciers such as lobate debris aprons (LDA) could have hosted chemolithotrophic communities, making Mars’ present glaciers candidates for life preservation. This study characterizes glacial processes on both Earth and Mars. Chemical weathering at Robertson Glacier, a small alpine glacier in the Canadian Rocky Mountains, is examined with a multidisciplinary approach. The relative proportions of differing dissolution reactions at various stages in the glacial system are empirically determined using aqueous geochemistry. Synthesis of laboratory and orbital thermal infrared spectroscopy allows identification of dissolution rinds on hand samples and characterization of carbonate dissolution signals at orbital scales, while chemical and morphological evidence for thin, discontinuous weathering rinds at microscales are evident from electron microscopy. Subglacial dissolution rates are found to outpace those of the proglacial till plain; biologically-mediated pyrite oxidation drives the bulk of this acidic weathering. Second, the area-elevation relationship, or hypsometry, of LDA in the midlatitudes of Mars is characterized. These glaciers are believed to have formed ~500 Ma during a climate excursion. Hypsometric measurements of these debris-covered glaciers enable insight into past flow regimes and drive predictions about past climate scenarios. The LDA in this study fall into three major groups, strongly dependent on basal elevation, implying regional and climatic controls on ice formation and flow. I show that biologically-mediated mineral reactions drive high subglacial dissolution rates, such that variations within the valley can be detected with remote sensing techniques. In future work, these insights can be applied to examining Mars’ glacial regions for signs of chemical alteration and biosignatures. / Dissertation/Thesis / Doctoral Dissertation Geological Sciences 2015