Inaug.-diss.--Jena. / Lebenslauf.

No description available.

Thesis (M.S.)--University of Wisconsin--Madison, 1983. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 93-95).

Natural calcium carbonates, such as foraminifera and speleothems, are ubiquitous on the Earth’s surface and are essential subjects of study to the field of paleoclimatology. In particular, climate proxies using stable isotope and/or trace element concentrations of marine or continental carbonates largely rely on laboratory calibration studies in which carbonates are synthesized and their geochemical properties are carefully quantified. The boron isotope compositions of marine carbonates are a potentially powerful tool for the reconstruction of ancient seawater pH. If proven reliable, this tracer will allow systematic recording of paleooceanographic conditions, greatly assisting climatologists identifying historical fluctuations in atmospheric carbon dioxide concentrations. The boron isotope-pH proxy relies on the hypothesis that only the charged borate ion, possessing a distinct boron isotope composition as a function of pH, is incorporated into the carbonate crystal lattice. In this study, abiotic calcite was synthesized in high ionic strength solutions (0.7 mol/kg) across a range of controlled pH conditions (low pH ~ 7.15, mid pH ~ 8.35 and high pH ~ 9.15). The magnitude of boron isotope fractionation (δ11B) was determined to quantify the pH-dependence of δ11Bcalcite between the carbonate and the precipitating solution. The observed increase in boron isotope composition of calcite with pH is consistent with preferential incorporation of borate ion into the crystal lattice, however the sensitivity of the acid dissociation and isotope equilibrium constants render it difficult to ascertain its exclusive contribution to the boron isotope composition of calcite. Observed non-equilibrium effects further mask the interpretation of the underlying mechanisms, which must be understood precisely to validate the proxy. Ultimately, the relationship between the boron isotope composition of marine carbonates and ocean pH may provide objective evidence for ocean-CO2 system alterations possibly stemming from human-induced climate change. This research also evaluated the temperature- and pH-dependence of oxygen isotope fractionation (between calcite and water) in high ionic strength systems at 10, 25 and 40 °C over a pH range of 7.46-9.43. Our study is the first to assess oxygen isotope effects and fractionation behaviour under these varied conditions while employing the constant addition method. Preliminary results support several working hypotheses in the field and have proven consistent with previously untested theoretical predictions. / Thesis / Master of Science (MSc)

The Burdigalian Saumane-Venasque carbonate succession is located in the Rhodano-Provençal basin of southeastern France. These carbonates accumulated in a paleovalley that was flooded by marine waters. This marine embayment was filled by carbonates composed of twelve different facies. These sediments form two thick third-order sequences (S1 & S2) and several, thinner higher-order sequences (S1a, S1b, S1c). S1a is composed of quartzose grainstones with barnacles, echinoids, and bivalves derived from a rocky substrate paleocommunity in a high-energy, open-marine environment during the early phases of sea level rise. Compound dunes of S1a and S1b are composed of bryozoans and echinoids that are mixed with bioclasts from seagrass facies. Pervasive cross-bedded grainstones grade upward into low-energy mudstones and packstones of the S1 highstand. Bryozoan thickets populated sequence 2 during the second sea level cycle. Seven different phases of cement, including cloudy epitaxial, fibrous, isopachous columnar, isopachous equant, clear epitaxial, blocky, and pendant types, can be distinguished in these limestones. Marine hardgrounds are present throughout the area as steep, stepped margins in tidal channels. Marine cements are interpreted to have precipitated in the upper portion of subaqueous dunes with their location controlled by sedimentation rate and tidal pumping. Zoned epitaxial cements are interpreted to record shifts in the paleo-water table related to fluctuations in sea level throughout the Miocene in the Rhodano-Provençal basin. Shallow burial pressure dissolution features are present throughout the deposit. They are interpreted to result from extended exposure to fresh water, which produced grains that were particularly susceptible to compaction. The Saumane-Venasque temperate carbonates are different in that they were lithified without significant burial diagenesis, a situation that resulted from multiple sources of cement from marine and meteoric waters. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2009-09-04 16:00:33.914

No description available.

Late diagenetic, fault-controlled dolomitisation has received much interest as it is an important host for MVT-mineralisation and hydrocarbons, and an excellent proxy for fluid flow and reaction in carbonate systems. The source of fluids of sufficient volume and the correct chemistry to explain the volume of dolostone is much debated. Recent work has shown how seawater convection along deep-seated crustal lineaments is focused in zones of structural complexity. Since dolomitisation is favoured where there is a precursor high magnesium calcite or dolostone, it is possible that such a process is a critical precursor to the formation of these late diagenetic dolostones from evolved brines during extension and transpression. In the Pennine Basin and North Wales, UK, late diagenetic fault/fracture controlled dolostones developed on the margins of Mississippian carbonate platforms that grew on the rotated footwalls of normal faults and a basement of Lower Palaeozoic metasediments. Conceptual models for their formation focus on expulsion of fluids from Serphukovian-Bashkirian sediments within adjacent hanging wall basins, by compactional dewatering or rupture of overpressured compartments and seismic pumping. This project aims to determine the source, composition and drive mechanism of fluids that formed a large (~60km2), non-stratabound dolostone body exposed within the Viséan sediments on the southern margin of the Derbyshire Platform, through a combined regional sedimentological, diagenetic and structural framework using multiscale, interdisciplinary techniques. Techniques include field observation, transmitted light and CL analysis, bulk major and trace element analysis including rare earth elements, stable isotope (oxygen/carbon), and strontium isotope analysis. The Derbyshire Platform underwent burial, several episodes of fluid-flow, and multiple phases of diagenetic overprinting. The products of fluid circulation in this area consist of dolomitisation and Mississippi Valley-type (MVT) mineralisation, affecting the carbonates of the Lower Carboniferous (Viséan) succession. Dolomitisation on the Derbyshire Platform is aligned to deep-seated basement faults and extrusive, intraformational volcanic beds, and five dolostone phases have been identified. These are present as matrix replacive and cement phases that are spatially and temporally related to deep seated structural lineaments. It is proposed that stratabound, early post-rift dolomitisation resulted from the geothermal convection of a mixed meteoric-seawater that interacted with the Viséan extrusive and intrusive volcanics on the Derbyshire Platform, providing additional magnesium for dolomitisation. This previously undescribed model of dolomitisation is key to explaining the anomalously large quantity of dolomitisation observed on the Derbyshire Platform and has implications to other carbonate platforms where dolomitisation is interpreted as fault-controlled. Subsequent phases of dolomitisation are fault-controlled, with each phase becoming increasingly confined to fractures. Timing of dolomitisation is interpreted to be a Carboniferous event, with later mineralisation also being of late Carboniferous in age, with basin de-watering on to the platform via faults/fracture systems and the development of pockets of overpressuring. Illite-smectite clay transformations within Viséan basinal sediments provided the necessary magnesium required within select fault/fracture systems. Consequently, burial calcite cements and MVT mineralisation was precipitated within fractures and dissolution-enhanced secondary porosity, with fluids derived from the overlying Namurian succession which also acted as the seal. This project provides a step-change in our ability to predict the location of late diagenetic fault/fracture controlled dolomitisation in rift basins by demonstrating the importance of dolomitisation by mixed meteoric-seawater on platform margins to the localisation of late diagenetic dolostone bodies. It also highlights the complex interplay between basin kinematics, host rock permeability and timing of fluid supply through episodic fault reactivation, connecting platforms to basin compartments, which ultimately controlled the positioning of dolostone geobodies on platform margins. This has implications to the exploration of both minerals and hydrocarbon within dolostone hosts, and will inform studies of fluid transfer and reaction in carbonate systems.

In matrix acidizing, the goal is to dissolve minerals in the rock to increase well productivity. This is accomplished by injecting an application-specific solution of acid into the formation at a pressure between the pore pressure and fracture pressure. A hydrochloric acid solution is used in carbonate reservoirs, which actually dissolves the calcite rock matrix in the form of conductive channels called wormholes. These wormholes propagate from the wellbore out into the reservoir, bypassing the damaged zone. In matrix acidizing of carbonates, there are four parameters that affect performance: the concentration of calcite present, injection rate of the acid, reaction type, and heterogeneity. Of these parameters, this paper will focus on how rock heterogeneity affects performance. To do this, a coreflood and acidizing apparatus was used to acidize heterogeneous limestone core samples. Rock characterizations and volumetric measurements were considered with the results from these experiments, which made it possible to correlate and quantify the results with rock and volume parameters. It was found that the core samples with more and larger heterogeneities generally required less acid (measured in pore volumes) to achieve breakthrough, that is, a wormhole created axially from one end of the core to the other. This value for pore volumes to breakthrough was one to two orders of magnitude less than more homogeneous samples. The general procedure and best practices for acidizing the core samples is also detailed in this thesis. This procedure was followed for preparation, coreflooding, and acidizing for all core samples.

Thèse de doctorat : Géosciences : Vandoeuvre-les-Nancy, INPL : 2005. / Titre provenant de l'écran-titre. Bibliogr.

Reproduction de : Thèse de doctorat : Sciences des agroressources : Toulouse, INPT : 2005. / Titre provenant de l'écran-titre. Bibliogr. 598 réf.