The late Paleocene to early Eocene was a prolonged period of global warming punctuated by abrupt intervals of rapid temperature rise. These hyperthermal events, especially including the Paleocene-Eocene thermal maximum, are characterized by negative carbon isotope excursions (CIEs), which signify massive input of 13C-depleted carbon. A widely-discussed mechanism to explain such carbon injection is destabilization and degassing of methane hydrates in marine sediment. Although large amounts of methane hydrate deposits should have existed during the late Paleocene and early Eocene, evidence has been limited. This study documents late Paleocene and early Eocene siderite-dominated carbonate concretions hosted in turbidites of the Dukla Nappe, Outer Carpathians, Poland. These concretions have delta13C ranges attributable to formation in methanogenic environments. Furthermore, grain-to-grain relationships and preserved sedimentary fabrics indicate authigenic formation prior to compaction. Given that they were deposited in sufficient water depth to host stable hydrates despite elevated ocean temperatures, these concretions provide supporting evidence of active methanogenesis and the accumulation of methane hydrates during the late Paleocene and early Eocene.

<p>Assessment of the potentially acidic, heavy metal-ladenleachates that leave deposits of sulfide ore mill tailings andevaluation of various possible options for mill tailingremediation are scientific problems of increasing practicalimportance. High costs may be associated with the mill tailingremediation, not least after recent changes in Swedish andEuropean environmental legislation. This thesis presents amethodology for studying and quantifying geochemical processesthat contribute to generation of so-called acid mine drainage(AMD). The methodology builds from first principles regardinggeochemical processes, and is based on geochemicalcharacterisation of the mill tailings combined with explicitmodel quantification of the effect of factors, such astemperature, pH, and mineral (BET) surface area, that influencemineral weathering rates. Application of the modellingmethodology to a case study site, Impoundment 1, Kristineberg,northern Sweden, including quantification of slow processesthrough literature rate laws, successfully reproduced the pHand relative concentrations of major ions in the impoundmentgroundwater. Absolute concentrations of most major ions, withthe exception of Zn, were 1-2 orders of magnitude higher in themodel than in the field, which is consistent with the commonlyobserved scale dependence of mineral weathering rates; however,application of a single calibration factor, X_r=10^-2, to all weathering rate expressions, sufficed toaccount for this apparent scale dependence.</p><p>Subsequent laboratory determination of mineral weatheringrates in Impoundment 1 tailings indicated that rates for themajor minerals pyrite (FeS₂) and aluminosilicates were in fact 1-2 orders ofmagnitude lower in the ~50-year-old tailings than ratesreported in the literature. Weathering rates of chalcopyrite(CuFeS₂) and sphalerite (ZnS) were by contrast 1-3 ordersof magnitude greater than predicted by the literature rate lawsthat were used in the modelling study. While the mechanism ofZn release requires further investigation for improved forwardmodel prediction, the underestimation of Zn concentration inImpoundment 1 by the model was resolved. The laboratory studyfurthermore indicated that the weathering rates of most majorminerals exhibited the same dependence on pH, temperature andsurface area as reported in the literature, and therebysupported the use of literature rate laws for model assessmentof dominant geochemical processes in tailings deposits, onceallowance is made for lower rates in older tailingsmaterial.</p><p>Analysis of the dominant geochemical processes in the modelof Impoundment 1 indicated that slow weathering ofaluminosilicate minerals provided the bulk of protonattenuation and, as a result, considerably affected the rate ofdepletion of fast-reacting pH-buffering minerals. Inclusion ofthe kinetics of aluminosilicate dissolution and of thefeedbacks between slow and fast processes is thus potentiallycrucial for prediction of pH and its long-term evolution. Thesensitivity of modelled groundwater composition and pH to ironredox reactions, such as may be accelerated by acidophilicbacteria, indicated that, while iron redox cycling was low atthe present case study site, quantification of microbialmediation of these reactions may be necessary for predictingAMD quality under other conditions. The laboratory studies alsoindicated that application of common sterilisation techniques,such as is necessary for study of relative contributions ofabiotic and biotic weathering processes, had little effect onthe long-term (>30 days) abiotic element release rates inthe tailings.</p><p>This study suggests that within certain limits, which appearnarrower than currently recognised in industrial predictionpractices, it is possible to predict the weathering behaviourof major minerals, and hence proton release and attenuation, inbase metal tailings under field conditions.</p>

Thesis (Ph. D.)--University of Oklahoma, 1993. / Includes bibliographical references (leaves 253-267).

Thesis (M. Sc.)--University of Queensland, 2003. / Includes bibliographical references.

This study documents the magmatic, hydrothermal and supergene mineralogy and geochemistry of phosphorus and rare earth elements in carbonatite complexes using examples from Tundulu (Malawi), Sokli (Finland), Siilinjarvi (Finland) and Kaluwe (Zambia). In carbonatites, phosphorus averages 1-2% P20S and forms the minerals fluorapatite and monazite. Hydrothermal and supergene processes enrich fluorapatite in Na and REEs through vitusite-type exchanges which lead to formation of vitusite, belovite and britholite; and in CO2 through anti-francolite substitutions. The highest rare earth element contents are found in late-stage ankerite carbonatites or similar rocks of low temperature origin (T < S(XtC) and in hydrothermally altered rocks, where they occur mainly as fluorocarbonates or carbonates. Such minerals are consistent with the REEs having been transported in form of mixed fluoride-carbonate complexes. The mineral paragenesis in hydrothermal veins suggests that different fluorocarbonates precipitated depending on the activity of Ca supplied to the fluid by the wall rocks. The various minerals are modelled to form by simple combinations of calcite (CaCO:v and bastnaesite (REEC03F) molecules. A secondary characteristic feature of these reactions is that extreme heavy rare earth enrichment occurs if the wall rocks are apatite-rich. Petrogenetic modelling using REEs suggests that carbonatites are unlikely to be derived from carbonated silicate magmas by fractional crystallisation or liquid immiscibility. These findings are supported by ex solution temperatures of about 9S0·C recorded using the calcitedolomite geothermometer for quenched lapilli from the Kaluwe carbonatite.

More than 80% of the exposed area of the Acatlan Complex was mapped and new outcrops of eclogites (Xayacatlan Formation), granitoids (Esperanza, Hornos, Teticic), and volcanic rocks (Cosoltepec and Tecomate Formations) were identified. 44 selected samples from the new outcrops were geochemically analyzed to establish the tectono-magmatic affinity. Volcanic rocks of the Petlalcingo Group suggest an oceanic setting (MORB and OIB), while bimodal rocks of the Tecomate Formation represent an intraplate event (WPB), in addition to an inherited arc signature. Most granitoids of the Acatlan Complex are peraluminous and classify as S type intrusions derived from crustal melting. These plutons straddle the VAG+ Syn-ColG and WPG fields in a Nb-Y discriminant diagram and are considered as syn-tectonic, late-tectonic and post-tectonic granites. Based on the main geologic, stratigraphic, structural and geochemical data it is suggested that the Petlalcingo Group represents a sedimentary sequence deposited in distal passive margin correlated with those siliciclastic deposits of the Early Paleozoic bordering the western margin of Gondwana. The Piaxtla Group (Xayacatlan and Esperanza Granitoids) represents an allochthonous unit deformed, metamorphosed and emplaced over the Petlalcingo Group during the Silurian orogeny (Caledonian) caused by the collision of peri-Gondwanan terranes (Avalon, Oaxaquia) and the subsequent approaching of Gondwana. During the Early Devonian, the Tecomate Formation was deposited because of the relaxation of the Silurian orogen. Finally the subsequent southward translation of Gondwana produced an intense deformation and low grade metamorphism into the Tecomate Formation (Acadian orogeny). Upper Paleozoic sediments deposited over the Acatlan Complex delimit its evolution.

This study investigates the contrasting tectonic settings in western Mexico and the controls they exert on porphyry copper deposits. Igneous rock affinities are deduced by integrating existing lithologic, geophysical, and geochemical information with new major-, trace-, rare earth-element, radiogenic isotope, and mineral phase compositional data. Regional findings are compared with theGeology of porphyry complexes in cratonic (Cuatro Hermanos) and accreted settings (Tameapa). Geochemical results identify four tectonic domains. Lower Cretaceous volcano-sedimentary successions are underlain by oceanic crust represented by the Bacurato Ophiolite. This domain is bordered on the south by the Lower Cretaceous San Pablo island arc Complex, on the west by much thicker crust (>30 km) and Jurassic and/or older sedimentary assemblages of Precambrian provenance, and on the north by the Upper Triassic Sonobari back-arc Complex. Plutonic rocks intruded the four domains. Upper Cretaceous anatectic plutons from a collisional setting have S- or I-type characteristics depending on the host rock they intrude. Combined Sr, Nd, and O isotope results from Upper Cretaceous and Laramide granodiorites show a primitive-to-evolved (εNd(I) = +4.6 to -3.8) gradient from central Sinaloa toward the north, west, and south, identifying the presence of Lower Cretaceous oceanic crust and volcanogenic materials well into southeastern Sonora. At Cuatro Hermanos, batholith (≈59 Ma) and porphyry (56 Ma) suites are broadly cogenetic and contaminated with significant radiogenic crust (εNd(I) = -3.3 to -4.0). Relative to batholith, porphyry magmas assimilated lesser sedimentary material, and are not well homogenized. At Tameapa, batholith (57 Ma) and porphyry (53 Ma) suites were derived from a mantle source, volcanogenic materials, and/or oceanic crust. Adjacent, coeval, and compositionally comparable batholithic intrusions exhibit disparate radiogenic signatures (εNd(I) = +3.1 and -2.5), indicating magma or source heterogeneity. Geochemistry of porphyries points to very high assimilation to fractionation ratios, extraction from a residual melt, heterogeneity, and magma chamber recharge. Faults have substantially rotated and dismembered both porphyry systems, as previously recognized at Cuatro Hermanos. However, Tameapa is the first deposit-scale documentation of large-magnitude extension observed in Sinaloa. Both lack of consanguinity of porphyries with well-homogenized host batholith and amount of extension have exploration significance in the region.

No description available.

<p>Production of oil and gas from unconventional natural gas reservoirs such as impermeable organic-rich shale formations was made possible through the use of horizontal drilling and high volume slick water hydraulic fracturing (HVHF). This combination of technologies has changed the energy landscape in the Unites States and possibly provided a vast new energy source from multiple sedimentary basins in the United States (Kargbo et al., 2010; Kerr, 2010) (Figure 1). HVHF requires large volumes of water (~5 million gallons/well) (Lutz et al., 2013) injected under high pressure to stimulate methane release from the fracture systems in the shale formations. The process is conducted within low-permeability formations, which include organic-rich shale rocks that are often the source rock for overlying conventional oil and gas reservoirs but do not easily transport gas to the well bore without stimulation. Once the permeability of the target formation is increased to a level that oil and gas can be recovered, pressure is released and 20-30% of the fluid that was injected flows back up to the surface through the well (Lutz et al., 2013). The remaining 70% stays underground, either lost to adjacent formations or imbed within the formation itself.</p><p>While HVHF operations rapidly expanded in many shale plays (e.g., Marcellus, Fayetteville), the possible negative environmental impacts remained un-quantified but a debated topic (Howarth et al., 2011). This dissertation focuses on quantification and evaluation of several water resources for evidence of contamination from HVHF. My hypotheses are: (1) HVHF have distinctive chemical and isotopic fingerprints that are different from other potential contamination sources; and (2) these fingerprints could be identified in aquifers and surface water systems.</p><p>I tested these hypotheses in two shallow drinking water aquifers overlying current unconventional gas development, northeastern Pennsylvania and north-central Arkansas, and one area of surface water disposal in western Pennsylvania. I used specific geochemical (Br, Cl, SO4, Na, Ca, Mg, Ba, Sr, B, and Li) and isotopic (87Sr/86Sr, 2H/H, 18O/16O, &#948;11B, and 228Ra/ 226Ra) tracers to characterize the target-formation brines and delineate possible contamination. The combined geochemical fingerprint distinguished hydraulic fracturing fluids and brines from other types of contamination that could influence water quality (e.g., road salt, sewage, acid mine drainage). </p><p>In Pennsylvania (Chapter 1), geochemical and isotopic data shows no direct evidence of contamination in shallow drinking-water aquifers associated with natural gas extraction of the Marcellus Formation. The data instead demonstrated that brine with the same geochemical (Br/Cl, Sr/Cl, and Ba/Cl) and isotopic fingerprint (87Sr/86Sr) of the Marcellus brine was likely naturally present in the shallow formations prior to the most recent oil and gas development. The data indicates that there may be areas in northeastern Pennsylvania that may be at increased risk of contamination from HVHF because of the presence of natural pathways that connect the shallow drinking water aquifers with deeper formations. This Chapter was published in Proceedings of the National Academy of Sciences in July 2012.</p><p>A very different result was observed in Arkansas (Chapter 2). While the shallow groundwater data indicated that there was no direct evidence of contamination, there was also no indication of hydrodynamic connections between the deeper formation brine and the shallow aquifers. Indeed 87Sr/86Sr, &#948;11B, 18O, and 2H values exclude Fayetteville Formation water as a source of salinity in shallow aquifers in the study area. The combined studies indicate that site and basin-specific studies of groundwater quality are necessary in order to evaluate the potential for contamination from HVHF. The Chapter was published in Applied Geochemistry in May 2013.</p><p>Surface water disposal of hydraulic fracturing fluids and brines (Chapter 3) clearly impacted western Pennsylvania sediment and water quality. Sediments in the stream at the point of effluent discharge from a treatment facility indicate radium activities 200 times higher than any background values. The 228Ra/226Ra ratios in the sediments also indicate that the source of contamination is likely the recent treatment and disposal of Marcellus brine. Impacts were also observed farther downstream. The concentrations of bromide and chloride in the effluent were so high that an increase in the concentrations measured in the stream was elevated almost two kilometers downstream. Chapter 3 was submitted to Environmental Science and Technology in May 2013.</p><p>Overall, this thesis aims to establish inorganic geochemical and isotopic tools for identification of hydraulic fracturing fluids in the environment and assess their possible impact on both surface and groundwater resources.</p> / Dissertation

No description available.