Upper Jurassic sediments from the Inner Moray Basin have been analysed using a variety of organic geochemical techniques. Shales belonging to the Kimmeridge Clay and Heather/Brora Formations may be readily distinguished using molecular parameters, bulk geochemical data and the results of transmitted light kerogen microscopy. Oxfordian sediments are characteristically more organic lean and sulphur poor than their ?Volgian - Kimmeridgian counterparts; they also contain a more significant terrestrially derived organic matter component. Lipid fractions in the remainder of the succession are typically dominated by the products of marine algal phytoplankton and bacteria. Detailed investigation of the distribution of biological marker compounds indicates that the nuclear demethylated hopanes are confined exclusively to sediments of ?Volgian - Kimmeridgian age in this basin. This feature, together with other more subtle, non-source specific variations may be attributed to a decrease in the dissolved oxygen content of the water column throughout the Upper Jurassic. All maturity measurements concur that in this region the Upper Jurassic sediments are insufficiently mature to have generated or expelled significant volumes of petroleum at any stage throughout their geological history. A range of maturities is nevertheless recognized which permits a ranking of the individual wells, and indicates that shales overlying the Beatrice reservoir have experienced the greatest thermal stress. A marked discrepancy in the maturities of contemporaneous sediments from two groups of wells presently at the same burial depth, has also been identified. This is largely consistent with the observed variation in geothermal gradients and the distribution of Kimmeridgian sands across the basin. Kinetic modelling using the biological marker maturity parameters has established that in the west 1km of sediment has been removed following Tertiary inversion of the basin. Results indicate that in the east, a figure of 700-800m is more appropriate. Potential source rock lithologies from the margins of the basin have also been examined. These included the Jurassic sediments in the Helmsdale outlier and Middle Devonian lacustrine laminites from Caithness. A Middle Devonian component to the Beatrice crude is strongly suggested by the similarity of their steroid alkane distributions.

<p> Two hydrothermal experiments were performed using sandstone core material from the Norwegian North Sea with synthetic brines reacted at approximately 150&deg;C and 450 bars, temperature and pressure calculated to simulate a depth of burial of approximately 4 km. The results of the experiments were analyzed with geochemical modeling and with chemical and petrographic analyses. Geochemical modeling with several computer programs indicated that the experimental fluid was undersaturated with respect to K-feldspar, kaolinite, and illite, but supersaturated with respect to muscovite. Chemical analysis with inductively-coupled plasma mass spectrometry indicated that the fluid reached saturation with respect to K-feldspar. Petrographic analysis with scanning electron microscopy and energy-dispersive scanning indicated that changes took place over the course of the experiments in both the clay and non-clay mineral fractions, and this result was verified by X-ray diffraction analysis that indicated dissolution of both K-feldspar and illite and formation of muscovite. These converging lines of evidence indicate that significant changes took place in the clay mineral fraction of the experimental sandstone core material, reacted at realistic basin temperature, pressure and geochemical conditions, over the course of several weeks.</p>

The Cripple Creek district, Colorado is renowned for its epithermal gold telluride veins which have produced over 21 million ounces of gold from an intensely altered alkaline diatreme complex (total production + economic resources of >900 tons Au, geologic resource >>1000 tons). Gold mineralization principally occurs as telluride minerals hosted by swarms of narrow veins composed of quartz ± fluorite, carbonate, adularia, pyrite > barite/celestite and accessory base metal sulfides. Mineralized hydrothermal breccias are also found in the district, along with low-grade, bulk tonnage resources that are targets of current mining activities. Newly recognized is a complex history of hydrothermal alteration and magmatism that led up to, and continued past the development of gold mineralization. These include the development of large volumes of low-temperature, alkali feldspar-rich styles of alteration, and more restricted volumes of high temperature, pyroxene and biotite-rich types. Gold mineralization is associated with voluminous K-feldspar + pyrite ± carbonate alteration that largely postdates igneous activity, and these are widely developed in the upper ∼1000 m of the volcanic complex. These follow a complex magmatic history characterized by at least three cycles of recharge. Although voluminous sulfate (anhydrite) and sulfide-rich styles of mineralization were also developed in the latest stages of hydrothermal activity, a remarkable aspect of Cripple Creek is the distinct underdevelopment of acid styles of alteration; feldspar and carbonate-rich styles of alteration predominate at all levels of exposure. The link between alkaline magmatism and gold deposits has been long recognized, but relatively recent discoveries of large, high grade deposits (Ladolam, Philippines, Porgera, Papua New Guinea), along with continued production from districts like Cripple Creek, encourages continued exploration. Salient characteristics shared by these deposits include telluride-rich mineralization accompanied by extensive carbonation, and voluminous K-metasomatism. Likewise, hydrolytic (acid) alteration tends to be poorly developed in many alkaline systems. This has important environmental implications, as the high acid buffering potential makes these deposits environmentally favorable to mine. The potential in alkaline systems for large and high grade deposits, coupled with the common lack of recognition of their distinctive styles of alteration and mineralization, makes these a compelling exploration target.

<p> Cretaceous Period. There is limited research on organic carbon content of the Pierre Shale in South Dakota. Frequent volcanic eruptions combined with climate change resulted in an increase in carbon dioxide in the atmosphere, leading to decreases in marine oxygen content. Decreasing marine oxygen has been attributed to higher amounts of preserved organic matter in marine sediment. Impact of volcanic ash deposition in the Cretaceous Interior Seaway has not been thoroughly studied. The Pierre Shale also contains the Crow Creek Member, a 5 foot thick layer of unconsolidated sand and rip-up clasts which may indicate a high-energy depositional event. Some hypothesize that it was deposited by a tsunami generated by the Manson impact. Others believe the Crow Creek Member is evidence of a marine low-stand that occurred before the Bearpaw Cyclothem. It is possible that the depositional event that deposited the Crow Creek Member may have led to increases in organic carbon preservation depending on the burial rates and amount of organic carbon preserved. </p><p> To investigate the connection between volcanic ash deposition, the Crow Creek Member deposition, and organic matter preservation of the coastal Cretaceous Interior Seaway, stable isotope geochemistry, trace element geochemistry, and total organic carbon analyses were performed on a 500 foot core drilled near Fort Pierre, South Dakota. Ash beds were identified using X-ray diffraction analysis. Core sampling was driven by location of the Crow Creek Member (above below and within one foot) and by location of ash beds (above below and within one inch), but samples were also taken based on highest and lowest gamma ray values for each five foot (1.52m) core segment. Core sampling was restricted because every other five foot (1.52 meter) section of the Treedam core segement was available for sampling. Statistical T-tests and Z-tests were performed on sample data to determine if there was a significant difference in geochemical signatures between core deposited before and after ash bed deposition and Crow Creek Member deposition. Results and T and Z statistical analyses show no significant changes in stable isotopes nor trace elements as a result of ash bed deposition nor the Crow Creek Member depositional event. Results also indicate that variability of the coastal brackish marine system made any significant trends harder to isolate on such a small scale. Overall &delta;¹³C_org signatures ( -27 to -26 &permil;) indicate that the Cretaceous Interior Seaway was deposited in a brackish shallow marine environment and that there were no drastic changes in sea level throughout the deposition of the Pierre Shale Group that was sampled (Gregory Member up through Virgin Creek Member). The &delta;<p style="font-variant: small-caps">15</p>N data range (-6 to +1 &permil;) show that fixed nitrogen was scarce during the deposition of the Pierre Shale and that most of the available marine nitrogen was likely fixed by cyanobacteria.</p>

The Toarcian, Early Jurassic, Oceanic Anoxic Event (T-OAE: ~183 Ma) was characterized by globally synchronous deposition of sediments rich in organic carbon (black shales), and is associated with an abrupt negative carbon isotope excursion, disrupting a positive carbon-isotope excursion during the tenuicostatum–serpentinum ammonite Zone boundary. The T-OAE has been extensively studied in northern and southern Europe, but evidence from the southern hemisphere is limited. New geochemical data from the tenuicostatum–hoelderi (~serpentinum) Andean ammonite Zone, from the Neuquén Basin, Argentina provides evidence for the global imprint of the event. The event is recorded in bulk-sediment from Arroyo Lapa (North and South) and Arroyo Serrucho with δ¹³C_org values of -30‰ – -32.5‰ and δ¹³C values from fossil wood fall to -30.7 ‰, isotopic ratios that are comparable to those identified in Europe for the T-OAE. Hydrogen Index (HI) data for the T-OAE in Argentina give values ranging from 12 to 425 mg HC/ g TOC, indicating a mixture of terrestrial and marine organic components. Pristane/Phytane ratios and pyrite framboid distribution data indicative of anoxic conditions occur at some levels, and new δ^98/95Mo data, with values ranging from ~ -0.2 to 0.78 ‰, which contrast with previously published molybdenum-isotope values from T-OAE black shales of northern Europe. Sedimentological data also reveals a marine transgression during the tenuicostatum–hoelderi Andean ammonite zone.

<p> The middle member of the Eagle Ford formation is a heterogeneous, carbonate-shale unit that is a focus of unconventional oil and gas exploration in southern Texas. Exploration results have been mixed because of the apparent heterogeneity of the member. In this study, the extent of heterogeneities in the Eagle Ford on the &ldquo;bedding-scale&rdquo; were examined by evaluating changes in organic and inorganic geochemistry. Samples were collected vertically in outcrop covering four non-consecutive parasequences. These samples were analyzed using a Rock Eval 6 Analyzer&trade; to determine source rock generative potential and a Niton&trade; XRF to evaluate inorganic geochemistry to identify changes in paleoredox conditions, paleoproductivity, and clastic influx. From pyrolysis data, it is determined that Parasequence 1 potentially displays an increase in source rock potential, Parasequence 2 potentially displays a constant source rock potential, and Parasequences 3 and 4 potentially display overall decreases in source rock potential during deposition. From the inferred paleoredox conditions, paleoproductivity, and clastic influx, it is determined that Parasequence 1 experienced a potential increase in oxygen abundance, Parasequence 2 experienced a potential decrease in oxygen abundance, and Parasequences 3 and 4 potentially experienced increases in oxygen abundance during deposition. It is concluded that geochemical heterogeneities do exist on a bedding scale within the parasequences of the middle member of the Eagle Ford. Additional comprehensive sampling and analysis is recommended in the future in order to tie these data to subsurface data for economic application.</p>

Ureilite meteorites are the second largest class of achondrite meteorites. They are perhaps the most enigmatic of all classes of meteorites and the dilemma over how they were formed has perplexed the meteoritic community for over a decade. This research was undertaken to illuminate the details of the petrogenesis of ureilites through the collection of trace element data. The results presented here indicate that many of the petrogenesis hypotheses promoted are no longer tenable and that the available data on ureilites are not sufficient to unravel the mystery of their origin. This dissertation discusses the data collected using two techniques: neutron activation analysis and inductively coupled plasma-mass spectrometry. Specific procedures required to study the ureilites (due to low concentrations of some trace elements) are delineated. Results are presented for the following elements: Ca, Co, Zn, Ga, Cu, Cs, Rb, Sr, Mo, Y, Ba, REE, Hf, W, Re and Ir. The results lead to the conclusion that the ureilites must be considered a mixture of materials--an original ultramafic rock formed by melting of processed source material combined with carbonaceous material added after the ultramafic formation. This conclusion explains the trace element chemical signatures and is supported by the age information obtained from Sm-Nd and Rb-Sr isotopic systems.

The central part of the Front Range mineral belt, Colorado, is a Precambrian crystalline basement terrain intruded by early Tertiary porphyries and closely associated mesothermal ore deposits. The ore deposits are gold- and silver-bearing base metal sulphide-quartz veins arranged in more or less well developed concentric mineral zones centred on concealed porphyry plutons. Central areas of pyritic mineralisation are surrounded by peripheral zone of galena-sphalerite-bearing veins, often separated by a transitional zone of composite mineralisation. Molybdenite-bearing and uraninite-bearing veins are locally abundant proximal to the central pyritic zones and are closely associated spatially and temporally with highly evolved quartz bostonite intrusions. The mineral veins are enveloped in narrow selvages of sericitized and argillized wallrock and are entirely fracture controlled. A low density lithogeochemical survey of the country rocks revealed strong lithological controls on the distributions of selected trace elements and radiation emission values. Positive Rb/Sr anomalies are tentatively linked to concealed intrusions, and corresponding positive anomalies of Pb, Zn, Mo and W are associated with known molybdenite mineralisation. Sericitized rocks are characterised by low Sr and enhanced Rb, Zn, Pb, Mo and Ag values, and areas of depleted country rock Sr values may be related to vein wallrock alteration. D/H and <SUP>18</SUP> O/<SUP>16</SUP> O signatures of fresh country rocks indicate variable magmatic water overprinting and similar analyses of sericitised rocks show that alteration was accomplished by magmatic hydrothermal fluids at 340<SUP>o</SUP> -515<SUP>o</SUP> C. Mineralisation and alteration in the area were caused by hydrothermal fluids evolved from highly differentiated Laramide quartz bostonite intrusions. K-Ar ages of ca. 62 Ma have been obtained from alteration sericites from the peripheral mineral zone. Similar studies in the central pyritic zone have yielded ages of ca. 59 Ma suggesting the existence of long lived hydrothermal activity in the area characterised by widespread high-temperature alteration, followed by thermal decay and collapse towards core zones. The ore deposits investigated during this study display numerous features in common with porphyry-style and other intrusive-related mineralisation characteristic of Cordilleran terrains, but also exhibit significant differences. The combination of these features contribute to the distinct and possibly unique character of these mineral deposits.

<p> Stable isotope analysis of thirty-five samples from the Northwestern Coast Mountains indicates a complex fluid history related to terrane accretion, metamorphism, and magmatism. The greenschist to amphibolite facies metasedimentary rocks from the Western Metamorphic Belt have variable &delta;D and &delta;¹⁸O values that appear to be in isotopic equilibrium with metamorphic fluids at low water-rock ratio conditions. Carbon isotope values indicate organic rich protoliths. Stable isotope values from the Coast Shear Zone indicate the involvement of both magmatic and meteoric-hydrothermal fluids during deformation, in contrast to meteoric-free fluid systems related to Au-mineralization along strike to the north (Goldfarb et al., 1988). The Coast Mountain Batholith and Central Gneiss Complex have homogeneous &delta;D and &delta;¹⁸O values that indicate magmatic fluids at low water-rock ratio (Magaritz and Taylor, 1976). Further to the east, large amounts of meteoric-hydrothermal fluids circulated through a network of ductile-to-brittle normal faults (Andronicos et al., 2003; Heah, 1990).</p>

<p> The Davis-Schrimpf Seep Field is a cluster of about 50 transtension-related geothermal seeps in the Imperial Valley, southeastern California. Five temperature time-series were collected from four features and compared to one another, against prior time-series, and to local seismicity. Loggers placed in separate vents within one seep returned moderate anti-correlation. Vents may selectively clog and unclog. Clogging frequencies explaining the observed level of negative correlation were given. Loggers placed in the same vent produced 87-92% positive correlation. It is therefore likely that the vast majority of temperature data measured with loggers possesses meaningful accuracy. Loggers placed in separate seeps exhibited correlation close to or greater than the statistically significant 60% threshold. I propose two lineaments provide a hydraulic connection between these seeps. Two M_w>3.0 earthquake swarms, including one M_w>4.0 event, within 24 kilometers showed possible linkage with >5 degree Celsius temperature perturbations. Seepage warmed 14.5-36.8 degrees Celsius over 5-7 years.</p>