MSc, Faculty of Science, University of the Witwatersrand, 2011 / The 35.3 million year old, 85 km diameter, Chesapeake Bay impact structure (CBIS) in Virginia, USA, is one of the best preserved complex marine impact structures on Earth and is associated with the North American tektite strewn field. Three drill cores (Eyreville A, B and C) were obtained from the Chesapeake Bay impact structure during 2005-2006 by the CBIS Deep Drilling Project in conjunction with the International Continental Scientific Drilling Program (ICDP) and the United States Geological Survey (USGS). The drill cores intersected crystalline basement rocks, impactites, and impactrelated and post-impact sediments. This study focuses on the impactite sequence of the Eyreville B drill core. The primary focus has been to examine and understand the conditions and processes involved in the formation of the crater-fill impactite sequence, and the provenance of the impactites, through detailed lithostratigraphic, petrographic and geochemical analysis. The Eyreville B drill core intersected 154 m of impactites between the depths of 1397.16 and 1551.19 m. The impactite sequence is divided into the upper (1397.16 to 1474.05 m) and the lower (1474.05 to 1551.19 m) impactite units. The upper impactites are matrixsupported (23.5 rel% of total clast count) and characterised by suevite, clast-rich impact melt rock and cataclastic gneiss blocks, whereas the lower impactites are clast-supported (19.8 rel% of total clast count) and are dominated by polymict impact breccia and cataclastic gneiss boulders and blocks. The suevites comprise melt and lithic clasts from sedimentary (predominantly shale and sandstone) and igneous (such as granitoid and quartz pegmatoid) target rocks in an unsorted matrix composed of mineral (primarily quartz, feldspar and micas) and lithic clasts. The polymict impact breccias are primarily composed of metamorphic clasts such as phyllite, mica schist and felsic and mafic gneiss, and are largely, but not completely devoid of melt clasts. The majority of clasts in the impactite sequence closely resemble the granitoid, pegmatoid, calc-silicate, amphibolite and mica schist lithologies found in the underlying basement-derived succession and megablocks in the overlying sedimentary clast breccia. Overall, the crystalline (igneous and metamorphic) and sedimentary clasts contribute 62.3 and 20.8 vol%, respectively, of iv the total lithic clast composition which is comparable to 58.2 (crystalline) and 26.0 (sedimentary) vol% for the latest published results. The impactites are generally heterogeneous in terms of their chemical compositions. The impactite samples display enrichment in FeO+MgO in comparison to the target rock lithologies, with smaller abundances of K2O and Na2O, with little to no CaO. Throughout the impactite sequence, the suevites display the largest variety in chemical composition due to the heterogeneity of the clasts. The overall abundance of melt clasts varies from 22.1 vol% (of the total clast population) in the upper impactites to 2.5 vol% (of the total clast population) in the lower impactites. Melt clasts are generally flattened and elongated and display laminar flow structures (schlieren), with fractured terminations. Most melts are highly vesiculated and altered to phyllosilicate minerals. Overall, melt clasts show a general decrease in size with depth. Observations indicate that no coherent melt sheet was intersected; impact melt rock was only noted in the impactite sequence at depths between 1402.02 and 1407.49 m and 1450.22 and 1451.22 m. Melt clasts are heterogeneous in terms of their chemical compositions and are generally SiO2-rich and represent the melting and mixing of different mineral (quartz, feldspar and phyllosilicates) types derived from the target lithologies. This finding is comparable to the observations noted in the recent published literature. On average, 23.6 rel% of all quartz grains in the upper impactite unit display one or more PDF (planar deformation features) sets, with this number decreasing to 13.33 rel% for the lower impactite unit. A general decrease in average shock pressure with depth has been noted, which is consistent with the decrease in other shock features and melt clast abundance from the upper to lower impactites. A maximum of 3 PDF sets in the quartz grains, in the upper impactites, were noted; however, mostly 1 or 2 PDF sets were observed. Diaplectic glass has been noted in the melt clasts and is present predominantly in the upper impactites. No PDFs in feldspar grains have been noted. v A small, low temperature impact-induced hydrothermal system (220 – 300 °C) affected the material within the crater, which is evident from veins and patches of quartz, calcite, secondary phyllosilicate minerals (smectite), zeolites, secondary pyrite and chalcopyrite, as well as other sulphides. The upper and lower impactites show differing petrographic, geochemical and shock characteristics, suggesting that they were formed by different mechanisms. The upper suevites (upper part of the impactite sequence) are composed of fallback debris from the collapsing ejecta plume or curtain, whereas the suevites (S3 and S2) represent a mixture of the ground-surge material and fallback debris from the collapsing ejecta plume. The impact melt rocks are interpreted as either detached remnants of the melt lining the transient crater or piles of melt derived from fallback debris. It is proposed that the lower suevites (S1) and polymict impact breccia represent ground-surge deposits at the base of and behind the advancing ejecta curtain, modified by slumping and mixing of unshocked material from the outer crater walls. The cataclastic gneiss blocks and boulders slumped in from the outer transient crater walls and were incorporated into the ground-surge deposits. This study of the impactite sequence from the Chesapeake Bay impact structure has provided new insights into the formation of the impactite sequence as well as that of the Chesapeake Bay impact structure. Research such as this allows for further understanding and discussions regarding marine cratering processes (impact processes and impact-generated deposits) and emplacement mechanisms for impact craters. Essentially a study such as this provides material for further extensive research into the formation of marine impact craters and comprehensive modelling.

Thesis (M.S. - Hydrology and Water Resources)--University of Arizona, 1984. / Includes bibliographical references (leaves 65-68).

abstract: Meteorites and their components can be used to unravel the history of the early Solar System. Carbonaceous chondrites are meteorites that originated from undifferentiated parent bodies that formed within a few million years of the beginning of the Solar System. These meteorites contain calcium-aluminum-rich inclusions (CAIs), which are the oldest dated solids in the Solar System at ~4.567 billion years old and thus preserve a record of the earliest stage of Solar System formation. The isotopic compositions of CAIs and bulk carbonaceous chondrites can be used to identify the sources of material inherited by the protoplanetary disk, assess the degree of mixing in the disk, and evaluate sample origins and potential genetic relationships between parent bodies. In particular, mass-independent Cr and Ti isotopic compositions have proven to be especially useful for these purposes. In this work, I first developed new methods for the chemical separation of Cr and Ti, improving the reliability of existing methods to ensure consistent yields and accurate isotopic measurements. I then measured the Cr and Ti isotopic compositions of CAIs from CV and CK chondrites to determine the extent of isotopic heterogeneity in the CAI-forming region and assess the role of CAIs in the preservation of planetary-scale isotopic anomalies. My results show that all measured CAIs originated from a common isotopic reservoir that incorporated material from at least three distinct nucleosynthetic sources and preserved limited isotopic heterogeneity. These results also suggest that planetary-scale isotopic anomalies cannot be attributed solely to the transport of CAIs from one part of the solar nebula to another. I finally measured the Cr and Ti isotopic compositions of bulk CM, CO, and ungrouped chondrites to evaluate the relationship between CM and CO chondrites, which have been suggested to originate from either distinct but related parent bodies or a common compositionally heterogeneous parent body. My results suggest that CM, CO, and related ungrouped chondrites originated from distinct parent bodies that formed from similar precursor materials in nearby formation regions. These results may have implications for asteroid samples returned by the OSIRIS-REx and Hayabusa2 missions. / Dissertation/Thesis / Doctoral Dissertation Geological Sciences 2020

<p>Biodegradation of petroleum hydrocarbons by microorganisms is one of the most effective methods used to remediate environmental systems. However, much of what is known is based on the ability of (mostly bacterial) species to degrade hydrocarbons under enrichment conditions in a laboratory setting. In order to refine biodegradation as a remediation method, there is a critical need to understand the dynamics and mechanisms of microbial communities under <em>in situ </em>conditions. The goal of this dissertation was to provide insight and knowledge into the function of microbial communities in petroleum-contaminated environments using a combination of DNA, lipid and isotopic analyses. Microbial biomass, community structure, carbon sources were assessed at two study sites: (1) a former industrial facility contaminated by PAHs and (2) coastal salt marshes impacted by the <em>Deepwater Horizon</em> oil spill.</p> <p>Isotopic analyses of soils collected from the PAH-contaminated site revealed that microbial carbon sources were derived from vegetation and/or natural organic matter present in soils matter rather than PAHs. Similarly, microbial community structure remained consistent across samples and there were no observed shifts in phylotype diversity with increasing levels of PAHs. Bioaccessibility assays revealed that a large fraction of soil-borne PAHs at the site are not bioavailable to microorganisms; thus, highlighting the importance of environmental factors to <em>in situ</em> biodegradation.</p> <p>Biodegradation of <em>Deepwater Horizon </em>spilled oil was detected in salt marsh sediments such that petroleum-derived carbon was a primary carbon source for indigenous microbial communities in the months following the spill. Likewise, pyrosequencing of all three microbial domains showed an increase in the relative of abundance of taxonomic groups known to include hydrocarbon-degrading species, such as <em>Sphingomonadales</em>. These results suggest that Gulf of Mexico marsh sediments have considerable biodegradation potential and that natural attenuation may be feasible remediation strategy in this region.</p> / Doctor of Philosophy (PhD)

A suite of samples consisting of twenty-two crude oils and eight sedimentary rocks has been analysed for biological marker compounds by GC-MS. The sedimentary rocks are rich in carbonate minerals and the crude oils were reported to have been derived from carbonate source rocks. These samples are from a variety of geographical origins, geological ages and depositional environments. They consistently contain a homologous series of 30-nor-17 [alpha] (H)-hopanes. Seven homologues (C28 - C34) of the 30-nor-17 [alpha](H)-hopane series have been identified. These compounds appear to be useful biological markers for samples having carbonate associations.A series of 25,30-bisnor-17 [alpha] (H)-hopanes has been observed in a severely biodegraded crude oil of probable carbonate origin. This observation, together with the well-established enrichment of normal hopanes demethylated at position 25 in severely biodegraded crude oils, suggests that the presence of this series of hopanes indicates severe biodegradation of crude oils originating from carbonate-rich source rocks.Another series of hopanes which was previously unreported, the 2-methyl-30-nor-1 [alpha] (H)-hopanes, has also been observed in the carbonate samples. Seven members (C29-C35) of this homologous series have been identified in this study. This series appears to be associated with carbonate rocks deposited under extreme reducing conditions.The biological marker compounds in another sample suite comprising twelve sediments and three crude oils from the North Sumatra Basin, Indonesia, have also been analysed by GC-MS as part of a correlation study. Sediment samples classified as shales, carbonaceous shales and calcareous shales have been shown to contain very different biomarkers. These distinctive biomarkers have enabled the source characteristics of the crude oils to be inferred. Two crude oils have been recognised ++ / with similar biomarker characteristics to the shales and one crude oil has the characteristics of the calcareous shale. The distinctive features of the carbonaceous shale were not observed in the crude oils. This study therefore provides an excellent example of how the 30-nor-17 [alpha] (H)-hopane compounds can be useful in oil-source rock correlation studies.

Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Geological Sciences." Includes bibliographical references (p. 278-287).

A Cl stable isotope fractionation factor between amphibole and fluid has been determined at 700 °C and 0.2 GPa. Rates of isotope exchange between pargasite and water at 600-800 °C were slow; therefore synthesis of amphibole in the presence of a fluid was necessary to facilitate the incorporation of Cl into amphibole. Hastingsite was synthesized from an oxide mixture and reacted with a NaCl-bearing supercritical fluid for periods of 3 to 14 days, approximately at the wüstite-magnetite buffer. Based on these synthesis-reaction experiments, the fractionation between hastingsite and a NaCl-bearing solution (~20000 ppm Cl) at 700 °C is 103lnαamphibole-fluid = 0.19‰ ± 0.23‰. These data display near zero fractionation at 700 °C, but suggest that amphibole is slightly enriched in 37Cl relative to the fluid, in agreement with empirical and theoretical results. / text

Thesis (M. Sc.)--University of Adelaide, Dept. of Geology and Mineralogy, 1988. / Includes bibliographical references (leaves [1-13]).

abstract: Hydrothermal systems are not the typical environments in which organic chemistry is studied. However the organic reactions happening there are increasingly implicated in non-trivial geochemical processes. For example, the origins of life, the formation and degradation of petroleum, and feeding the deep biosphere. These are environments where water is heated and pressurized until it has a polarity more typical of an organic solvent and an increased dissociation constant that decreases its pH. In addition, these environments host many transition metal oxide and sulfide minerals that are not inert bystanders to the chemistry happening around them. This thesis takes from the environment the complicated matrix of hot pressurized water, organic material, and minerals, and breaks it down, systematically, in the laboratory to probe the effects hydrothermal conditions and minerals have on the reactivity of model organic compounds. I conducted experiments at 300&deg;C and 100 MPa using water, organic reactants, and minerals. Methyl- and dimethyl-cyclohexane based reactants provided regio and sterio-chemical markers to indicate reaction mechanisms. Without minerals, I found that the cyclic alkanes undergo a series of reversible stepwise oxidation and hydration reactions forming alkenes-alcohols-ketones, and alkenes-dienes-aromatic rings. I also found the reactions to be reversible; the ketone was readily reduced to the alkane. When the reactions were carried out in the presence of minerals, there were sometimes dramatic effects including reaction rate enhancement and changes in product distributions. Minerals pushed the reaction in the direction of oxidation or reduction depending on the type of mineral used. The hydration reaction could be essentially &ldquo;turned off&rdquo; using pyrite (FeS2) and troilite (FeS), which eliminated formation of ketone products. In contrast, hematite (Fe2O3) and magnetite (Fe3O4) favored the hydration reaction and enhanced ketone production. Sphalerite (ZnS) was shown to act as a heterogeneous catalysis for alkane isomerization by activating the C-H bond and increasing reaction rates until thermodynamic equilibrium was reached. This suggests that the types of minerals present in hydrothermal environments will affect the functional group composition of organic material. Minerals and hot pressurized water may also have useful applications in organic chemistry as &ldquo;green&rdquo; reactants and catalysts. / Dissertation/Thesis / Ph.D. Chemistry 2013

The Sabie River Basalt Formation is a group of tholeiitic basaltic rocks erupted ca 190 Ma ago in the eastern zone of the Karoo Igneous Province of southern Africa. It is traceable over a distance of 700 km from Zululand, northwards along the Lebombo monocline into the Transvaal and south-east Zimbabwe. An abrupt compositional change in this formation occurs about halfway down its length in the vicinity of the Sabie and Komati Rivers: basalts to the north are known to be enriched in certain incompatible elements relative to basalts in the south, which are comparable in geochemistry to most basaltic rocks in the southern part of the Karoo Igneous Province. New data obtained in this work include 134 major and trace element whole-rock analyses, some 400 analyses of constituent minerals, 38 ⁸⁷Sr/⁸⁶Sr ratio determinations, 19 ¹⁴³Nd/¹⁴⁴Nd ratio determinations, 16 common Pb determinations and 12 oxygen isotope analyses. The "normal" (N) and "enriched" basaltic rocks are distinguished by differences in the concentrations of Ti, P, Zr, Nb, Y, La, Ce and Nd (high field strength elements). Broadly these differences are substantiated by K, Rb, Ba and Sr, but with much more overlap. The "enriched" group of basaltic rocks has been further subdivided into a low-Fe "enriched" (LFE) group and a high-Fe "enriched" group (HFE). The LFE-group basalts, which predominate at the base of the stratigraphic sections, are considered to be equivalent to basalts occurring in the N. Lebombo. In the central Lebombo N-group basalts predominate in the mid- and upper portions of the sections and HFE-group basalt occurs near the top of each section. Interbedding of all basalt groups occurs in the Sabie River section at the northern end of the study area, while the N- and HFE-group basalts are interbedded in the Crocodile and Komati River sections further to the south. The decrease in LFE-group basalt abundance southwards is accompanied by an increase in N-group basalt abundance. HFE-group basalts appear to be unique to the central Lebombo area of the Karoo Igneous Province and are volumetrically less significant than N- or LFE-group basalts. Petrogenetic models involving closed-system fractional crystallization; coupled assimilation (of granitic crust) fractional crystallization; replenished, tapped and fractionated magma chambers and partial melting are examined. Granitic crustal contamination appears to have been significant only in some samples of the N group where assimilation of granitic material has proceeded in a bulk fashion described by an AFC model. RTF models are dynamically more realistic than closed-system fractional crystallization models and explain increases in incompatible elements with decreasing MgO in the LFE and HFE groups. Variations in the N group, however, require varying degrees of partial melting of a N-type source to be explained fully. RTF models may explain the absence of any stratigraphic correlations of element abundances in the three groups. The HFE group may be related to an uncontaminated N-type parent composition by a combination of continued fractional crystallization from an N-group parent composition and varying degrees of partial melting of an N-type source. The only petrogenetic process by which the N and LFE groups may be related is different degrees of partial melting. However, this demands a source composition which has no resemblance on trace element and isotopic grounds, to observed mantle xenolith compositions. The preferred model is one in which the LFE group is derived from old sub-cratonic mantle similar to garnet-bearing "cold" peridotite xenoliths and the N group from a source similar in composition to estimates of primitive mantle. The existence of two types of mantle derived continental flood basalt magmas occurs in other Mesozoic basalt provinces in "southern" Gondwanaland (e.g. Kirwanveggan of Antarctica, Etendeka of Namibia and the Parana Basin of South America). It is suggested that there is a geographical association of LFE-type basalts with Archaean crust (or Archaean crust re-worked in low temperature - high pressure events) and N-type basalts with post-Archaean crust (or Archaean crust re-worked in high temperature - low pressure events). This model suggests the derivation of the LFE group, from old sub-cratonic lithospheric mantle relatively enriched in incompatible elements and the N group being derived from more recently accreted and less enriched lithospheric mantle underlying younger crustal terraines.