The decomposition temperature of schorl was found to be 880 ± 10°C using X-ray and optical methods. The main crystalline product in decomposed schorl and dravite was found to be a boron containing mullrte, the composition of this phase was found to become closer to that of mullite (3Al203.2Si02) as the decomposition temperature was increased. The size of these possibly slightly.orientated needle shaped microcrystals was approximately 25 ± 10 u by 3 ± 2 u by 3 ± 2 u. The main decompostion products obtained in reducing conditions, in addition to the boron containing mudite, were hercynite {FeO-Al203} at low temperatures and oC— iron at higher temperatures. The decomposition temperature:; of schorl in the presence of activated charcoal was found to be at least 60^C lower than that for air decomposed schorl. This decrease was thought to be associated wcth the formation of hercynite by a low temperature reaction between schorl and activated charcoal. The boric oxide and Iron oxide in air decomposed schorl were both extracted by dilute acid. The rate of extraction was found to increase as the original schorl decomposition temperature was increased. The activation energy for the extraction of boric oxide as a function of the schorl decomposition temperature was found to be equal to 19.2 ± 0.4 kcal/mole. This increase in the rate of extraction of boric oxide was suggested to be associated with the separation and growth of micro-regions of a boron rich phase within the silica-iron oxide amorphous matrix. The activation energy for the extraction of boric oxide as a function of the leaching temperature was found to be equal to 7.99 ± 0.19 kcal/mole, whilst the activation energy for the extraction of iron oxide from air decomposed schorl was found to be equal to 7.13 ± 1.06 kcal/mole. The similarity between these values and that of 6.8 kcal/mole for the activation energy oftacTid leaching of phase-separated borosilicate glass (138), was thought to provide further indirect evidence for the suggestion that the amorphous phase in decomposed schorl contains phase separated micro-regions. The rate of extraction of both boric oxide and iron from schorl decomposed in reducing conditions was found to be considerably faster than from air decomposed schorl. This increased extractability was thought to be connected with the presence of micro-crystals of iron in the decomposed reduced schorl. The boric oxide present in both schorl and dravlte was found to be extractable if water vapour was passed over the decomposed minerals at temperatures above 1000*c. The activation energy for the extraction of boric oxide by pyrohydrolysis from decomposed schorl was found to be equal to 85 ± 8 kcal/mole, whilst the activation energy for the extraction of boric oxide by pyrohydrolysis from both decomposed dravite and "pyrex" glass was found to be equal to 22 ±1 kcal/mole. The higher value was thought to be due to the incorporation of Fe2+ ions into the amorphous silica lattice in decomposed schorl. This process was suggested to lead to an increase in the energy barrier towards the diffusion of water vapour through the silica-iron oxide amorphous matrix to the boron rich reaction surface.

No description available.

This thesis presents, for the first time, direct evidence for the formation of magnetic minerals during hydrocarbon generation, it also reports on the nature and type of magnetic mineralogy formed during the generation of oil and gas. This thesis also reports experimental results that explain variations in magnetic mineralogy along potential crude oil migration paths in the Wessex Basin, southern England, UK. Potential oil-source rocks from the Wessex Basin, England, were pyrolysed (artificial maturation) at various temperatures under conditions similar to those for hydrocarbon-generation to reveal the formation of nano-metre sized magnetic minerals, mainly magnetite and pyrrhotite, with traces of greigite. The potential of these magnetic minerals to migrate along with the generated crude oil is also reported in this thesis. To assess the possibility of using magnetic characterisation to test for potential hydrocarbon migration, I examined the Wessex Basin, southern England, using 2D seismic data, geochemical analysis and mineral magnetic techniques. Potential hydrocarbon migration pathways from the hanging wall of the Purbeck fault into Sherwood Sandstone reservoir at Wytch Farm was identified via interpretation of 2D seismic data. Geochemical characterisation of oils extracted from core materials from the Wessex Basin revealed oils found at Stoborough and Waddock Cross are less mature than oils at Wytch Farm, which likely indicates spillage from the top of the reservoir at Wytch Farm due to regional tilting. In addition, the geochemical data from the core materials also show probable migration paths for oils found at Chickerell. Magnetic characterisation of reservoir core material (Bridport Sandstone and Inferior Oolite) revealed variations in magnetic signatures along potential migration routes, with variations also found with sampling depth. The magnetic signature was characterised using low-temperature magnetic remanence and hysteresis measurements, because much of the magnetic signature was found to be from nanoparticles that are thermally activated at room temperature (superparamagnetic). The study found magnetite predominates in the hydrocarbon proximal plume, pyrrhotite in the distal plume environment with mixed pyrrhotite and magnetite in shallow proximal plume environment. It is suggested that magnetic mineralogy has the potential to be used as a proxy for hydrocarbon migration identification in the future.

This study focuses on five zeolites: sodalite, zeolite A, linde type N, zeolite Y, and EMC-2, with SOD, LTA, LTN, FAU, and EMT framework topologies respectively. All of these zeolites have β-cages as the framework building units. The aims are to understand the conditions which control the formation of different zeolite phases and some of the physical properties of zeolite frameworks, mainly the framework exibility, and the capacity of β-cage to accommodate guest molecules such as water and methanol. The hydrothermal and microwave syntheses of zeolite with no organic structure directing agents require precise control of synthesis conditions and form the fundamental part of this study. Reaction temperature and synthesis time control the phase purity in zeolite A synthesis. A transformation from zeolite A to sodalite is observed and is related to framework density and reaction temperatures. Microwave syntheses of sodalite show that the batch compositions and methods of preparation also affect the as-synthesised zeolite phases and a new sodalite morphology is found. By using microwaves instead of traditional hydrothermal methods, one of the most complex zeolites, linde type N zeolite, was synthesised. This is the first study to report this new method. The newly defined extrinsic exibility window is studied on more depth in this work. While the intrinsic exibility is defined by the ability of an empty framework to flex with no distortions in the primary tetrahedral building units; the extrinsic exibility window is limited by the host-guest steric interactions between the framework and the extra framework contents. In zeolite Y, the extrinsic exibility window can be limited not only under compression, but also in expansion, as the β-cage in a maximally expanded framework lack the exibility to adapt to bulky contents such as a combination of methanol and water molecules. It is also found that the β-cage in zeolite Y can only accommodate a maximum number of two water molecules and one methanol molecule. The same phenomenon is observed in sodalite under compression. In the sodium form, the framework remains within its intrinsic exibility window when fluorinert is used as pressure transmitting media, as fluorinert does not enter the zeolite pores. However, an extrinsic exibility window is observed in both the sodium and sodium bromide forms with methanol/ethanol/water mixture as pressure transmitting media. An exception is seen in EMC-2. The intrinsic and extrinsic exibility windows are identical to each other. The presence of 18-crown-6 ether molecules in the pores does not affect the exibility window. The crown ether, despite its steric bulk, does not limit the geometric exibility of the framework since the cage of the EMT framework has enough space to accommodate the crown ether molecule and can adapt to the contraction. This shows that the extrinsic exibility window of zeolite frameworks is controlled not only by the extra framework contents, but also by the framework building units.

Calcium sulphate dihydrate is a compound important among those which form troublesome scale in distillation apparatus for the production of potable water from the sea. Among methods employed for the reduction of scale-formation is the use of certain substances which inhibit the crystallization of scale-forming materials. The present study is an investigation of some of the factors involved in the inhibition of crystallization from supersaturated solutions. The crystallization of CaSO4.2H2O, both seeded and unseeded, from solutions containing sodium chloride and sodium tripolyphosphate, has been studied as a function of the supersaturation and of the concentration of polyphosphate additive. The processes occurring have been monitored by following the concentrations of calcium and polyphosphate species in solution with time, using compleximetric and colorimetric analysis. Both in the seeded and unseeded crystallization, the presence of polyphosphate led to the inhibition of crystallization. Induction periods have been shown to be logarithmically related to supersaturation and additive concentration and in the seeded case to be dependent on the mass of seed crystals for small amounts of seed. The interaction between tripolyphosphate in solution and calcium sulphate dihydrate has been studied by measurements of concentration loss from solution and the take-up of polyphosphate shown to involve processes other than simple sorption. In contrast with sorption of polyphosphates by less soluble adsorbents, such as barium or strontium sulphates, the take-up by calcium sulphate dihydrate is suggested to involve in initiation of the deposition of a substance containing calcium and polyphosphate on to the crystals. The solid phases involved have been examined by chemical and infrared analysis. X-ray powder diffraction and electron microscopy.

No description available.

A broad palynological study has been made of field samples of Kimmeridgian to Berriasian age from a number of localities in Western Europe:- 1) Southern England - Dorset; Kimmeridgian - Berriasian. 2) Eastern England - Norfolk; Portlandian - Berriasian. 3) Northern England - Yorkshire; Kimmeridgian. 4) Northwest France - the Boulonnais; Kimmeridgian - Portlandian. 5) North Spain - RibadeseUa; ? Kimmeridgian • . 6) Portugal - Cabo Espichel; Kimmeridgian. An account of the origins, distribution and occurrence of various sedimentary organic materials (kerogens) is presented and the results obtained are discussed in the light of earlier accounts of the sedimentology, mineralogy, biostratigraphy and palaeogeography. Two applications of this data are demonstl'ated:- 1) Palynofacies types can be recognized which can be related to to environmental parameters such as distance from shore-line, water depth and turbulence. 2) The kerogen types present and their degree of maturation allow some comment to be made on the potential of the sediments for sourcing hydrocarbons. In particular it is demostrated that the highly bituminous Kimmeridgian sediments from Dorset and Yorkshire ha ve considerable potential for sourcing oil. Microplankton assemblages (dinoflagellate cysts and aed tarchs are recorded and described from the English and French sections which are well dated upon independent palaeontological evidence. The various taxa constituting the microplankton assemblages are - described and in part illustrated in a systematic section. 195 taxa and taxonomiC groupings are recorded; 10 new genera, 19 new species and 1 new subspecies are proposed; in addition the diagnosis of 4 genera and 5 species are emended, 5 genera and 8 species are treated as junior synonyms and rejected, and 20 new taxonomic combinations are proposed. The recorded taxa have been tabulated qualitatively for each of the sections and a series of informal microplankton zones and associations of local stratigraphic value have been established. The data from these charts has been used to compile a range chart which incorporates 52 selected "key-species" for the Upper Oxfordian - Berriasian interval. Earlier studies concerning Upper .;J.rassic and Lower Cretaceous microplankton are reviewed in light of the present study. Although the above biostratigraphic units are mainly of local stratigraphic value only, the observations and results presented here have been substantiated and enlarged upon by work currently being undertaken by the writer. It is concluded that the use of palynological assemblages will provide a useful tool for correlation purposes and the elucidation of the depositional histories of marine basins. Furthermore it is considered that the use of micro plankton will provide a reliable time - strati graphical control in marine sediments of Late Jurassic - Early Cretaceous age.

No description available.

No description available.

MicroRaman spectroscopy represents a powerful tool for the study of crystal structure and identification of materials. Despite being widely used in other areas of scientific research it has yet to become a routine analytical technique within the Earth Sciences. Case studies are used to describe the application of this technique. Using the different approaches available a variety of materials of a mineralogical and petrographic nature are used to assess the usefulness and applicability of the technique. Following a brief review of the fundamental theory of Raman scattering, a description of the analytical instruments is given and the format of the thesis explained. An existing database of mineral spectra is assessed, comprehensively edited and suggestions made for improvements. Mineral identification is implemented on several samples to emphasize advantages over other techniques. Investigations of changes in crystal structure are performed on biotite radiohaloes, zircons and quartz on the basis of spectra acquired. Dimension stone and brick provide examples of the suitability of microRaman spectroscopy to analysing the processes and transformations of natural materials, for industrial benefit. The potential to enhance the technique became evident and a gemstone macrochamber and 'well-plate' - type sample holder constructed to realise this. Circularly polarised light was investigated for collecting orientation-independent spectra. The ability to collect structural information over a micrometer scale in the form of maps and images makes the technique attractive to mineralogists. Lack of sample preparation, disparity of sample type and sensitivity are all advantages over XRD, a favoured technique in the investigations considered. MicroRaman spectroscopic study of minerals has been found to have few limitations. Notably, these are largely unpredictable fluorescence and potential for ambiguity of results. The technique has great prospects in the Earth Sciences and will become a routine analytical method.