Theses and Dissertations at Montana State University (MSU)
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Item Hydrogen production from mechanically-activated basalt under experimental conditions simulating subglacial environments(Montana State University - Bozeman, College of Letters & Science, 2019) Mitchell, Kari Rebecca; Chairperson, Graduate Committee: Mark L. SkidmoreShearing of rocks containing silicate followed by reaction with water has previously been shown to produce hydrogen under experimental conditions relevant to subglacial environments. The abiotic production of hydrogen, carbon dioxide, methane, and other hydrocarbon gases has also been demonstrated in laboratory comminution experiments on rocks from glaciated catchments. Thus, the generation of these biologically useful gases (e.g. hydrogen and methane) beneath glaciers could serve as a source of reductant capable of sustaining microbial ecosystems beneath the ice. Despite the ubiquitous nature of basalt on both Earth and other planetary bodies, production of hydrogen and other gases from basalt through mechanical shearing and reaction with water has not been demonstrated. Basalts were collected from glaciated catchments in Iceland to test whether hydrogen and other gases were produced under laboratory conditions simulating glacial comminution. Rock samples were milled under an inert atmosphere, after which water was added and hydrogen and methane production measured over time. An average of 6.6 nmol hydrogen and 2.6 nmol methane per gram rock were produced after 168 hours from basalt samples tested; additionally, hydrogen peroxide and radicals were produced during grinding. The abiogenic production of hydrogen and methane under these simulated subglacial basaltic environments demonstrated in this study also has implications for supporting subglacial microbial communities during periods of extended glaciation, such as glacial-interglacial cycles in the Pleistocene and during the pervasive low-latitude glaciation of the Cryogenian. This mechanism of hydrogen production also has implications for the potential for life on icy worlds like Mars.Item Characterization of subglacial till from Robertson Glacier, Alberta, Canada : implications for biogeochemical weathering(Montana State University - Bozeman, College of Letters & Science, 2013) Griggs, Russell Kelly; Chairperson, Graduate Committee: Mark L. SkidmorePhysical and biogeochemical weathering occurring during transport in the subglacial traction zone impacts the lithology and petrology of sediment in tills. Grain size distribution, particulate organic carbon (POC) content, and bulk/clay mineralogy of recently exposed tills from the terminus of Robertson Glacier, Alberta, Canada were characterized via sieving, laser diffractometry, loss-on-ignition, and X-ray diffraction/scanning electron microscopy (SEM) in order to describe physical and mineralogical properties of these tills. The matrix material of all tills exhibit a grain size distribution biased toward medium to coarse sand-sized particles and the dominant minerals are calcite, dolomite, quartz, and K-feldspar with lesser muscovite, pyrite, phlogopite, and chlorite. POC abundance ranges from 1.1 to 3.5 weight percent and is negatively correlated with grain size for grains from 125 - 2000 microns. POC abundance is also positively correlated with calcite abundance, especially for grains from 125 - 2000 microns. Pyrite is present at < 1% bulk abundance, with a significant portion of the pyrite observed via SEM as ~5-15 micron grains. The modal particle size of the till matrix of medium to coarse sand is consistent with limited physical weathering due to the short (< 3 km) subglacial transport distance and is comparable to that from a metasedimentary glaciated catchment in the Swiss Alps. The small grain size of pyrite produces a large reactive surface area, which supports its potential importance as a key chemical energy source for microbially-mediated chemical weathering.Item Geochemical evidence for microbially mediated subglacial mineral weathering(Montana State University - Bozeman, College of Letters & Science, 2007) Montross, Scott Norman; Chairperson, Graduate Committee: Mark L. SkidmoreInteractions between dilute meltwater and fine-grained, freshly comminuted debris at the bed of temperate glaciers liberate significant solute. The proportions of solute produced in the subglacial environment via biotic and abiotic processes remains unknown, however, this work suggests the biotic contribution is substantial. Laboratory analyses of microbiological and geochemical properties of sediment and meltwater from the Haut Glacier d'Arolla (HGA) indicates that a metabolically active microbial community exists in water-saturated sediments at the ice-bedrock interface. Basal sediment slurries and meltwater were incubated in the laboratory for 100 days under near in situ subglacial conditions. Relative proportions of solute produced via abiotic v. biotic mineral weathering were analyzed by comparing the evolved aqueous chemistry of biologically active (live) sediment slurries with sterilized controls.