Thesis (S.M.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2008. / Includes bibliographical references (p. 45-47). / Biogeochemical cycling of phosphate is a key component in the overall production rate of coastal ecosystems. Mineral phases in the near-shore sediments play a significant role in the return of phosphate remineralized in the upper sediments to the water column. Sequential Extraction (SEDEX) of the solid-phase associated P04-3 yielded reservoir profiles of phosphate at three sites off of the Massachusetts coast. These extractions found Fe-associated P04 to be the dominant phase associated with rapid porewater-solid P exchange. Additionally, a seasonal enrichment/depletion pattern of phosphate fluxes relative to total carbon was observed from the sediments. These observations established the behavior of phosphate in coastal sediments as interconnected with the ongoing Fe-cycling in the sediments as well. / by Richard Hunter Oates, Jr. / S.M.

The aim of this study was to arrive at a fundamental understanding of kimberlite weathering and of factors which affect the rate and extent of weathering. Weathering was evaluated by measuring the change in size distribution after immersing crushed kimberlite in solutions of various compositions. Reproducibility of the measurements was found to be good, with the cumulative mass passing a given size differing by 7% or less, as tested for various weathering conditions. Kimberlite mineralogy, specifically the swelling clay content, was found to play a central role: kimberlite ores containing no swelling clay were not prone to weathering under any of the conditions tested. The cation exchange capacity (CEC) correlates well with the swelling clay content and with the weathering behaviour. The cation exchange capacity may be used in conjunction with the swelling clay content, as a predictor of possible kimberlite behaviour; however, given the relative complexity and cost of measuring swelling clay content (by X-ray diffraction), the CEC is the preferred parameter for practical use. Cations in the weathering solution have a strong effect on kimberlite weathering; the strength of the effect followed the series Cu2+ > Li+ > Fe2+ > Ca2+ > Fe3+ > Mg2+, whereas K+ and NH4+ stabilised the kimberlite somewhat against weathering. This sequence was in reasonable correlation with the ionic potential (ratio of valency to ionic radius), but with exceptionally strong weathering effects of Cu2+, and (to a lesser extent) of Li+ and Fe2+. The strong effect of the latter group of cations may be related to their tendency to adsorb onto other crystal sites in addition to the interlayer – the associated change in surface energy can change the fracture behaviour of the kimberlite. Measurement of the layer spacing of the swelling clay (by X-ray diffraction) showed no correlation between the weathering effect of a cation and the associated thickness of the interlayer. For solutions of cupric ions, the identity of the anion (chloride or sulphate) has little effect on weathering. The size of the crushed kimberlite ore similarly has little effect on the relative extent of size degradation by weathering. The concentration of cupric ions affects weathering, as does the weathering time – although 85% of the weathering caused by 30 days' exposure was found to occur within the first 24 hours. Increasing the temperature to 40°C (in a magnesium chloride solution) also increased weathering strongly. The kinetics of exchange of cuprous and potassium ions was measured (for two different kimberlites); the apparent reaction order (with respect to the concentration of exchanging cations in solution) varied between 1 and 3.5, and exchange of potassium was more rapid. This work has practical implications for in-plant processing of kimberlite, possible alternative kimberlite processing routes which eliminate one or more crushing steps, and for the stability of mine tunnels which pass through kimberlite. / Thesis (PhD (Metallurgical Engineering))--University of Pretoria, 2006. / Materials Science and Metallurgical Engineering / PhD / unrestricted

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20390号 / 工博第4327号 / 新制||工||1671(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 作花 哲夫, 教授 安部 武志, 教授 佐藤 啓文 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20688号 / 工博第4385号 / 新制||工||1681(附属図書館) / 京都大学大学院工学研究科都市社会工学専攻 / (主査)教授 小池 克明, 教授 三ｹ田 均, 准教授 須崎 純一 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Bison produce trails, wallows, and trample grounds, visible in satellite imagery disturbing ~27,500 m2 at Yellowstone National Park (YNP; in USA) and ~10,700 m2 in Białowieża National Forest (BNF; in Poland and Belarus), and, without anthropogenic land change, these mega-traces persist in sand-dominated substrates for 6-26 years. The average wallow size ranges from ~17-40 m2, whereas the average trample ground varies in size from ~140-300 m2. Trail segments typically extend for ~260-380 m, but the longest trails at YNP traverse >3 km. Estimates of track volume indicate for a standard herd of 200 animals, over a daily distance of 10 km ~4000 m3 is pediturbated. Low sinuosity values of 1.16-1.10 characterize trails, and wallows display high aspect ratios >0.7, helping distinguish bison traces on the landscape. During the Holocene, as many as 40 million bison inhabited North America, so this study provides a qualitative baseline for considering the geomorphic ability of large ungulates.Caliper measurements indicate the surface expression of simulated bison tracks varies depending on the moisture content of the medium. The slope of the marginal ridges (MR) in dry (0% moisture by volume), moist (~10% moisture by volume) and wet (saturated) sand differ around the track perimeter, although the minimum slope of the marginal ridge increases with moisture content (dry sand ~10 cm, moist sand ~40 cm, wet sand ~20 cm). The maximum MR slope (~80°) occurs in a moist substrate. The aspect ratio of prints in wet sand is 0.60, reflecting the most elliptical hoofprint, whereas moist sand displayed the most circular track with an aspect ratio of 0.76. The interdigital angle decreased by ~5° with increasing moisture (dry = 56°, wet ≈ 51°). Photos document in dry sand, deformation fronts 2-3 cm in height are present, whereas in moist sand, transverse and radial cracks are present. In wet sand, debris flows form. Ground-penetrating radar (GPR) imaging reveals subsurface anomalies interpreted as undertracks and normal micro-faults. In dry sand, two poorly-defined sets of undertracks with 1 cm relief are visible 3-4 cm beneath the tracking surface. Normal faulting is absent. In moist and wet sand, 4-5 sets of detailed undertracks showing 2-3 cm of relief deform sediments 7-8 cm in depth. Several normal faults are present in moist and wet hoofprints. Combined surface and subsurface observations may indicate the moisture content of paleo-tracking surfaces, particularly if the substrate is saturated. When hoofprints are formed in an unfrozen substrate, freezing increases preservation potential. Partially thawed tracks are resistant to deflation (wind erosion), maintaining outlines of digits and the medial pocket until late stages of deflation. Billions of ungulate traces formed in aeolian periglacial settings may be preserved. Tracks exposed to aeolian action exhibit higher heavy-mineral concentrations (HMC) along marginal ridges (MR), which are detectable using low-field bulk magnetic susceptibility (MS). In situ tracks from Delaware and Virginia (USA) display marginal HMCs 3.7-10x greater than background MS, whereas in laboratory, simulated hoofprints show marginal HMCs 1.7x above background MS. HMCs readily occur in nature, so MS measurements of tracking surfaces may quantitatively indicate the length or intensity of aeolian processes. This experiment demonstrates hoofprints indented through a <1 mm thick HMC and subsequently exposed to 1 min wind gusts of 5-10 m/s form HMCs on the scale of 10’s of µSI. Billions of ungulate tracks displaying marginal HMCs are probably preserved, potentially providing a detailed regional paleo-wind record. / Geoscience

Phyllosilicates are widespread on Noachian to Early Hesperian terrains on Mars and can help constrain the planet’s geologic and environmental history, particularly its aqueous and redox history, which in turn can provide clues about past habitability. A range of ferrous and mixed-valence smectites were synthesized and then exposed to varying O2 fluxes under dry conditions to determine if Fe/Mg trioctahedral smectites can be oxidized without an aqueous medium to form dioctahedral smectites like those observed on the surface of Mars. The appearance of a secondary peak in some unaltered samples indicates a separate phase formed during synthesis, which remained throughout the oxidation process. Partial oxidation was achieved by all samples, but only those with the highest starting Fe3+ content reached almost complete oxidation. Rapid initial oxidation was observed for all samples, but seemed to subside before oxidation was complete, indicating the process becomes unfavorable after a certain point. All three O2 fluxes used in this study were successful in partially oxidizing the smectite samples but no correlation was observed between O2 flux and actual amount of oxidation, i.e., a higher O2 flux does not necessarily result in higher production of ferric iron. The process of oxidation did cause octahedral sheet contraction in some cases; however, in some samples octahedral sheet expansion was observed with oxidation. No additional phases were formed upon oxidation and no Fe ejection was observed. Overall, the amount of oxidation observed for all samples indicates that O2 alteration of trioctahedral smectites into dioctahedral smectites can proceed under dry conditions, meaning oxidation could have continued on Mars after surface water dried up. / Geology

This study investigates jarosite formation and stability patterns at the abandoned Davis Pyrite Mine in Rowe, Massachusetts. Jarosite, an iron-sulfate hydroxide, is found in acid mine drainage (AMD) environments, in acid sulfate soils, and on Mars. Jarosite and the iron oxides goethite and hematite are present at the site. Soil samples from the site were examined by XRD, SEM, and EDS. Five mineralogical areas were found, based on mineral abundance patterns. Jarosite exists in four of these areas. Two jarosite morphologies were identified. “Variable” jarosite, with partly-dissolved crystals of about 0.5 to 5 micrometers diameter, exists in spoil pile samples. “Donut” jarosite, with tightly-packed, sharp-edged crystals less than 0.5 micrometers that form a thin mantle on the surface of a second mineral, exists in native soil samples. Donut jarosite has not been previously characterized. These jarosite morphologies are controlled by the presence and relative mobility of pyrite oxidation products Fe and SO4, which in turn are controlled by water saturation levels. Three pathways are possible. On Path 1, both ions are mobile, go into solution, and variable jarosite forms at a distance from the pyrite source. On Path 2, only sulfur ions are mobile, an iron-oxide gossan develops. No jarosite forms. On Path 3, neither ion is mobile, and donut jarosite forms. On this path, Fe and SO4 ions are trapped in a thin film of stagnant water covering the pyrite. When sufficient ions are present, donut jarosite precipitates.

Indiana University-Purdue University Indianapolis (IUPUI) / The main objective of this work is to better quantify lunar surface minerals (agglutinate, clinopyroxene, orthopyroxene, plagioclase, olivine, ilmenite, and volcanic glass), particle sizes and the abundance of SMFe from the lunar soil characterization consortium (LSCC) dataset with our improved model based on Hapke's radiative transfer theory. The model is implemented for both forward and inverse modeling. Hapke's radiative transfer theory is implemented in the inverse model means Newton's method and least squares are jointly used to solve nonlinear questions rather than commonly used look-up Table (LUT). Although the effects of temperature and surface topography are incorporated into the implementation to improve the model performance for application of lunar spacecraft data, these effects cannot be extensively addressed in the current work because of the use of lab measured reflectance data. Our forward radiative transfer model (RTM) results show that the correlation coefficients between modeled and measured spectra are over 0.99. For the inverse model, the distribution of the calculated particle sizes is all within their measured range. The range of modeled SMFe for highland samples is 0.01% - 0.5 % and for mare samples is 0.03% - 1 %. The linear trend between SMFe and ferromagnetic resonance (Is) for all the LSCC samples is consistent with laboratory measurements. For quantifying lunar mineral abundances, the results show that the R-squared for the training samples (Is/FeO <= 65) are over 0.65 with plagioclase having highest correlation (0.94) and pyroxene the lowest (0.68). In the future work, the model needs to be improved for handling more mature lunar soil samples.

Several recent studies that have proposed MUSIC models for gibbsite surfaces have purported to achieve a very good fit with potentiometric titration data. However, in order to achieve such results, several significant parameters, such as the number of surface sites, site densities, and pKa values were sometimes re-introduced in the model as fitted parameters, and physically unrealistic modeling assumptions were sometimes used. In addition, recent evidence supports the idea that some of the gibbsite potentiometric titration data from these studies may be unreliable. In order to re-interpret the potentiometric titration data, we used several recently published methods. In order to detect possible problems with estimates of gibbsite basal and edge surface area, we synthesized two gibbsite samples with different aspect ratios and characterized their surface areas using BET, AFM, and computerized image analysis routines. We also estimated pKa values for acid/base reactions at gibbsite surfaces by applying a new bond-valence method to gibbsite (001)-type and (100)-type surface structures based on ab initio calculations. The resulting pKa estimates are not to be taken as precise values due to difficulties and assumptions associated with calculating reasonable ab initio surface structures. Instead, we believe they represent a more reasonable range than has been previously estimated. Using these estimates, we propose an improved MUSIC model for gibbsite, which seems to predict surface adsorption, not perfectly, but within a reasonable range for a number of titration data sets without re-introducing any of our estimated parameters as adjustable parameters. Discrepancies that exist between model predictions and various potentiometric titration data sets are likely due to error associated with potentiometric titrations and pKa predictions.

This study of ATR-IR involved taking spectra of various silicate minerals in powder samples, finding similarities and differences in nature, and locating various bands and intensities of absorption bands for identification and classification purposes. This study is limited to 4000-300 cm-1 with major emphasis on absorptions in the 2000-300 cm-1 region.