Two-phase systems of a liquid hydrocarbon mixture, containing medium molecular weight (C(,7)-C(,12)) aromatic and aliphatic hydrocarbons, and water were examined in both equilibrium and kinetic experiments. Knowledge of the aqueous solution behavior of liquid hydrocarbon mixtures is of importance in determining the fate of hydrocarbon components in such systems of an environmental or geologic nature. Solute concentrations were determined by solvent extraction followed by gas chromatography. The equilibrium solute concentration for a given component i (C(,i)) is related to the pure compound solubility (C(,i)('o)), mole fraction of component i in the hydrocarbon phase (x(,i(h))) and the activity coefficient of component i in the hydrocarbon phase ((gamma)(,i(h))) by the following: C(,i) = x(,i(h))(gamma)(,i(h))C(,i)('o). (gamma)(,i(h)) values determined for binary hydrocarbon mixtures using static vapor pressure measurements (at 20 and 70�C) and (gamma)(,i(h)) values determined using water solubility results (at 20 and 70�C) and the above equation did not differ significantly. This finding indicated that component aqueous phase activity coefficients do not decrease measurably in the presence of hydrocarbon co-solutes, in contradiction to Leinonen and Mackey, 1973 and Leinonen, 1976, and that the presence of water in the hydrocarbon phase is not a significant parameter at these temperatures. Some of the hydrocarbon systems (20�C) examined were: n-octane + 1-methylnaphthalene (also 70�C); tetralin + methylcyclohexane; ethylbenzene + n-octane; methylcyclohexane + 1-methylnaphthalene; 1,4-dimethylnaphthalene + n-octane; methylcyclohexane + n-octane; 1,4-dimethylnaphthalene + 1-methylnaphthalene; a 12-component JP-4 simulated jet fuel mixture and a 12-component JP-8 simulated jet fuel mixture. Methods for predicting multicomponent liquid hydrocarbon mixture solubilities were investigated. Non-equilibrium solutions resulting from water in contact with a liquid hydrocarbon mixture have solute concentration ratios that are essentially the same as those found under equilibrium conditions assuming that the hydrocarbon phase composition did not change substantially in the process. A surface renewal mass transfer model is used to explain this result. The mass transfer model can also be used to help explain non-equilibrium solute concentrations resulting from water in contact with a hydrocarbon phase of changing composition due primarily to evaporation.

Obsidian was considered a very important resource by Mesoamericans and understanding the major source regions is a key step towards comprehense the economy of Mesoamerican regions. Mesoamerica is divided into nine sub‐regions according to the locations of major obsidian sources and Zaragoza obsidian source is the dominant supply in the Zaragoza‐Oyameles sub‐region. The aim of this paper is to present new investigations into the geology and geochemistry of the previously understudied Zaragoza obsidian source. Subsequent to this, comparisons between Zaragoza source and other major sources across central Mexico were made in order to understand the nature of Mesoamerican obsidian sources. During the study, we discovered three chemically different flows exited in the field with Zaragoza‐1 and Zaragoza‐2 match the previously reported Zaragoza obsidian with just some chemical variations possibly due to combined effects of fractional crystallization and some other magmatic process. However, Gomez Sur obsidian flow, which is exposed on the Northern part of the study area, displayed similar but not exactly same chemical signals has previously defined Altotonga obsidian, which was thought to be the product of the same magma system as the Zaragoza obsidian. Based on chemical similarities and the fact that the spatial relationship between previous altotonga sample collection points and our Gomez Sur outcrops, we hypothesize that Gomez Sur and Altotonga obsidians might both be products from earlier eruptive activities. The Heterogeneity Index (HI index) values of 12 obsidian sources across central Mexico indicates that the presence of another flow or sub‐flows in obsidian field might be a common scene across central Mexico. / 1 / Heng Hu

acase@tulane.edu / Redox-sensitive trace metals tend to be more soluble under oxidizing conditions and less soluble under reducing conditions resulting in authigenic enrichments in oxygen-depleted sedimentary facies (Algeo and Rowe, 2012; P Ho et al., 2017; Tribovillard et al., 2006). Because of that, redox sensitive trace elements are used as paleoredox proxies to reconstruct redox status of the environment (Tribovillard et al., 2006). Unfortunately, we lack the quantitative understanding of many of these trace elements. One of the most important trace elements is tungsten. To contribute a better understanding of the biogeochemistry of tungsten to our community, I utilize laboratory experiments, geochemical modeling, and statistical methods to investigate the speciation, kinetics, and adsorption of tungsten in the environment. This thesis includes three major chapters. In the first major chapter, I performed a series of chemical experiments to explore the particle reactivity of tungstate and tetrathiotungstate in sulfidic solutions. I found that pyrite is a strong scavenger of W in aquatic environments. Our results indicate that the difference of specific adsorption between WO42– and WS42– may be attributed to their different inner-sphere complexation on the pyrite surface. Our results also show that WS42– is less particle reactive with respect to pyrite than MoS42–. In the second major chapter, I examined effect of acid on tungsten (W) sulfidation process as well as developed the Brønsted acid relationship, which provides a tool to predict the effect of acids on the kinetics of the thiolation reaction of W in natural waters. The results of laboratory experiments show that thiotungstate formation is first order with respect to both H2S and WO42- concentrations, and is catalyzed by acids. Therefore, low pH and high H2S concentrations both favor W thiolation. However, compared to molybdenum (Mo), thiolation of W is kinetically “sluggish”. The modeling results show that full thiolation of Mo requires ca. 110 days, whereas full thiolation of W requires ca. 50 years under a persistent euxinic condition such as the Black Sea. Our results indicate that the longer the period of euxinia, the higher chance of WS42- species in solutions and subsequently be incorporated into euxinic sediments as W-S species. In the last chapter, I successfully tested whether protonated mineral surfaces also catalyze the hydrolysis of tetrathiotungstate anions. Our results show that kaolin (Al2Si2O5[OH]4), aluminum oxide (γ-Al2O3), and titanium dioxide (TiO2) exert an appreciable catalytic effect on tetrathiotungstate hydrolysis. The data suggest that the pH dependent hydrolysis rate of WS42- for kaolin, γ-Al2O3, and TiO2 fall into two distinct groups, which consist two reaction pathways. The pH dependence of the mineral-catalyzed reactions suggest that acid surface sites on the mineral surfaces promote WS42- hydrolysis reactions. In the presence of UV-light, TiO2 substantially enhanced the hydrolysis rate of WS42- compared to identical experiments that were conducted in the absence of UV-light, we suggest the increased hydrolysis rate of WS42- in the presence of UV-light reflects the production of reactive oxygen species by TiO2. Due to the rapid development of nanotechnology, more engineered nanomaterials like TiO2 are introduced into the environment, which can impact the speciation and mobility of trace elements. Combined, the results in this thesis advance our understanding of mechanisms for W biogeochemistry in euxinic systems and will allow to facilitate reconstruction of paleodepositional conditions, paleoproductivity, and paleoredox. / 1 / Minming Cui

Dissolved and suspended particulate organic carbon (DOC, POC), nitrogen (DON, PON), phosphorus (DOP, POP) and inorganic nutrient distributions and elemental ratios were measured and evaluated for the Atlantic, Southern, and Pacific Oceans. Results indicate that DOC is remineralized during mean deep-water transport from the North Atlantic to the North Pacific. Elemental ratios for both dissolved organic matter (DOM) and particulate organic matter (POM) indicate that organic N is preferentially remineralized compared with organic C, while organic P is preferentialy remineralized relative to both organic C and N. Comparison between the DOM and POM pools further suggests that surface POM may be less refractory than concurrently sampled DOM. Major compound class compositions of ultrafiltered DOM (UDOM) in the North Atlantic, North Pacific and Chesapeake Bay indicate that the majority of UDOM was comprised mainly of a molecularly-uncharacterized fraction, followed by carbohydrates, proteins and lipids. Delta14C and delta 13C results of UDOM compound classes suggest that UDOM in Bay mouth and surface open ocean waters were similarly dominated by old, marine sources, while UDOM from the freshwater endmember was influenced by much younger terrestrial sources. Results indicate that DOM is comprised of different aged organic fractions and provide evidence for a potential organic "size"-age continuum; from low-molecular weight DOM (oldest) to UDOM (intermediate age) to POM (youngest). Lipid biomarker results indicate that North Atlantic and Pacific UDOM and POM were relatively more reactive at the surface compared with greater depths, coinciding with elemental C:P and N:P ratios greater than Redfield. Factor analyses suggest that there exists a "lability continuum" spanning from surface ocean POM to riverine and deep ocean UDOM. Terrigenous organic material was found at all Bay sites although autochthonous sources of organic matter were also important. Dark microbial incubations of DOM from the Pacific Subtropical Front and South Atlantic Bight indicate that open ocean DOM is relatively refractory over short time scales (less than 2 months). Experiments with plankton leachate DOM show that this sub-pool of DOM is relatively labile and is converted to refractory DOM within days. DOP is preferentially remineralized in all experiments compared with DOC or DON.

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Esfordi is a Kiruna-type Fe???P oxide deposit in the Bafq district of Iran. It formed within a predominantly rhyolitic volcanic sequence that formed in a continental margin tectonic regime and is of Cambrian age. The gently dipping, stratabound ore body is lenticular and displays a well-developed mineralogical zonal pattern. The Fe-oxide rich core contains a central zone of massive magnetite and a more hematitic brecciated rim. The overlying P-rich ore body contains massive and brecciated, apatite-rich variants with accessory hematite and actinolite. A zone of apatite-bearing veins and disseminations envelopes the Fe-oxide and P-rich zones and extends into overlying volcaniclastics that contain detrital magnetite ?? apatite clasts. The main ore zones are surrounded by Ca-rich alteration, dominated by actinolite, extending ~100 m into the more permeable overlying volcaniclastics. Beyond this envelope is widespread development of secondary K-feldspar. Mesoscopic and microscopic observations reveal a paragenetic sequence containing four generations of apatite. The early stage is a LREE-rich apatite 1 that occurs within the massive and brecciated magnetite core. The second generation is large and brecciated apatite 2, associated with hematite and actinolite. Both apatite 1 and 2 exhibit widespread dissolution and reprecipitation to form a LREE-poor granular apatite that is generally associated with quartz-carbonate??REE minerals. The final stage involved an overprint of LREE-poor apatite 3-carbonate-quartz-actinolite-chlorite-epidote??bastnaesite??synchesite extending into the host rocks. Fluid inclusions in apatite 1 have homogenisation temperatures of 375-425oC and indicate salinities of 14???18 wt. % NaCl. The magnetite displays low ???????O of -0.1???1.7 ???, suggesting precipitation from fluids with ???????O of 7.8???9.6 ??? at ~400oC, consistent with a magmatic source. Fluid inclusions in apatite 2 homogenise between 195???295oC with indicated salinities of 13???19 wt. % NaCl. The associated hematite displays ???????O of -0.2???2.3 ??? which would be in equilibrium with fluids having a ???????O of 10.7???13.0 ??? at ~250oC. Such enriched isotopic fluids suggest interaction of magmatic fluids with cooler saline fluids that were probably derived from the underlying carbonate-rich sequences. Fluid inclusions in apatite 3 and quartz homogenise at 145???155oC and, together with a quartz ???????O of 16.0???17.1 ???, suggests precipitation from a fluid with ???????O of -0.7???2.1 ??? that is likely to have resulted from the introduction of a cooler, less saline and isotopically depleted fluid (such as sea water). The results of this study clearly indicate a significant role for fluids in the evolution of the Esfordi deposit but do not preclude a role for immiscible Fe-oxide???P-rich melts in the initial stages of the mineralising process.

Rich gold-telluride lodes (steeply dipping and flatly dipping) and minor gold-quartz stockwork mineralization characterize the Kalgoorlie gold-field. The origin of these gold deposits, the relationship between deposits and then nature of the host rocks are the major problems considered in this thesis. Extensive diamond drilling at the essentially unmineralized southern end of the field provided excellent material for stratigraphic studies and for country rock analysis whilst ore samples were obtained from both mines and drill core.

Rich gold-telluride lodes (steeply dipping and flatly dipping) and minor gold-quartz stockwork mineralization characterize the Kalgoorlie gold-field. The origin of these gold deposits, the relationship between deposits and then nature of the host rocks are the major problems considered in this thesis. Extensive diamond drilling at the essentially unmineralized southern end of the field provided excellent material for stratigraphic studies and for country rock analysis whilst ore samples were obtained from both mines and drill core.