The crystallisation of salts in porous building materials is a principle agent of decay in historic monuments and archaeological sites, including the World Heritage Site of Petra, Jordan. Nonetheless, the mechanism of salt damage is still inadequately understood. This research was undertaken in order to examine the role of wind speed in the salt damage process. The first aim of the research was to evaluate the role of wind speed in salt crystallisation and distribution. The second aim was to monitor the microclimate conditions and salt distribution at selected monuments in Petra, in order to understand the extent and mechanism of salt damage at these monuments. The monitoring of the microclimate conditions included spot readings for wind speed, temperature and relative humidity taken during four fieldwork visits as well as continuous logging. The salt distribution was assessed by analysis of samples that were collected from different locations, depths and heights at the same monuments. The research also took into account the role of clay minerals in salt damage. The third aim of the research was to develop a salt simulation test that would include the effects of wind. The tests were undertaken with sandstone and limestone specimens under controlled environmental conditions, including low, high and fluctuating wind speed. The results have shown that wind speed has a significant impact on salt crystallisation and distribution in porous materials, and thus on decay rates, and that fluctuating wind speed enhances salt damage more than steady speeds. In addition, the research has suggested an unexpected relationship between pore structure and the behaviour of salts under different environmental conditions. The thesis concludes with recommendations for the conservation of the site of Petra. These include proposals for reducing the salt content of certain monuments and for protection against the effects of wind.

Sulfur-species in geological materials have detrimental consequences for geoenvirormental engineering. The research considers aspects of sampling, testing and assessment that were identified as in need of further investigation. Field and laboratory studies show that the distribution of sulfur-species with depth below ground level can be divided into three zones: an upper sulfate leached zone, an intermediate zone with sulfate-horizons and a lower sulfate-poor, sulfide-rich zone. Based on this zonation, a targeted sampling strategy for sulfur-species is presented and permits application of existing classifications for aggressive ground. Petrographic studies of mudrock aggregates reveal the variations in sulfur-species morphology. It is shown that both framboidal and euhedral pyrite can oxidise extensively and that expansion due to gypsum growth may comprise several stages. Dehydration of hydrous sulfate minerals during sample drying was found to be insignificant for typical sulfur-species concentrations. Where high levels of accuracy are required, air-drying (<40ºC) is suitable, however vacuum drying may be required to remove all water from clay soils. The UK gravimetric method for acid-soluble sulfate determination was found to suffer from numerous error sources, with ±0.1% S042- error possible. Use of ICP-OES/AES to quantify sulfate in an acid-extract improved accuracy by an order of magnitude, to an acceptable level for sulfate contents around the tolerance for geo-materials. ICP-OES/AES is recommended as the standard method, with gravimetry to be used only if the sample mass is increased ten-fold. A review of the limitations associated with derived chemical terms such as equivalent pyrite shows that each term relies heavily on assumptions that may not be valid under certain conditions, particularly in the presence of insoluble sulfates and organic sulfur. The geoenvirorunental implications of the research findings are discussed in the context of various ground engineering scenarios and best-practice recommendations are made.

This study has explored the phenomenon of basin-wide sand intrusion. Two case studies from regions with very different tectonic and depositional histories, host rock successions and intrusion geometries have been used to examine sand intrusion in the subsurface. Striking first-order similarities between the two contrasting case studies are apparent 1) the basin-wide nature of the sand intrusion event 2) the strong temporal link between the intrusion of sand and major tectonic events within the basin. It therefore appears likely that sand remobilisation in the subsurface and subsequent sand intrusion was triggered by earthquake activity. The case studies are presented as four papers produced for publication, supported by a review of previous work and a discussion of the case study results. A broad-based approach using a range of geological techniques was used to examine problems in our understanding associated with basin-wide fluid escape and sand intrusion. The first of the two case study areas consists of a region (in excess of 10,000 km<super>2 </super>) of large-scale conical sandstone intrusions hosted within a deep-water Eocene-Oligocene succession consisting of claystone and bio-siliceous ooze in Tranche 6 of the Faroe-Shetland Basin. The emplacement of the conical sandstone intrusions occurred during the Late Miocene, coincident with a phase of basin inversion. Polygonal faults were exploited as conduits to feed the conical intrusions, however intrusion propagation occurred along new fractures rather than exploiting the pre-existing polygonal fault network. The second case study is a region of sandstone pipes hosted within the sand-dominated rocks of the Middle Jurassic Carmel Formation and Entrada Sandstone in SE Utah. Pipes formed before the deposition of the Middle Jurassic Cannonvillle Member of the Entrada Sandstone across the region. Pipe formation was coincident with increased tectonic shortening and the inception of eastward tilting of the basin due to uplift to the west. Fluid-flow velocity during pipe formation is constrained to around 1.6 cms"1 based on calculations of settling velocity of grains present within the pipe fill.

One of the most critical geological/technical challenges affecting engineering projects in chalk with flints either for hydrocarbon/water exploration or infrastructural development is encountering flints, which mostly result in excessive wear or damage to cutting tools or drilling/tunnelling equipment. Overcoming this requires a regional understanding of the engineering properties of flints which are linked to various factors including the genesis/diagenesis of flints. To date, the genesis of flints remains debatable and the controls on engineering properties of flints on a regional basis have not been systematically investigated. This study sets to investigate: the genesis of flints, the engineering properties of flints across various geographical locations, the variations in these properties with colour, structures, origin, and morphology of flints, and the tectonic history of the host chalk. To achieve these objectives a series of physicomechanical and petrophysical tests on flints and associated structures sampled from the Danish, English and French chalks have been carried out. A drillability test focusing on the grey and dark brownish grey flints using a standard tricone bit to reflect the rock mass characteristics of flint has been conducted. Petrographic studies comprising scanning electron microscopy, scanning electron microcopy-cathodoluminescence and X-ray diffraction have then been applied to analyse the genesis, diagenesis, microstructures, microtexture, and mineral phase/composition of flints. Results support the biogenic origin of flints through a calcite-silica replacement process and illustrate that engineering properties of flints correlate with colour, origin, and the diagenesis of flints, plus the properties and tectonic history of the host chalk. This study demonstrates that physicomechanical properties of flints are controlled by their micro-structures/texture/fractures, structures, calcite inclusions and mineral compositions. The dark brownish grey flints with finer microtexture are the strongest, stiffest, densest, hardest, most abrasive and least porous materials with extremely high potentials to cause drill wear. By comparison, the grey flints located in a highly tectonized zone behave differently and are the weakest, less dense, less abrasive and the most porous flints with relatively lower potentials to cause drill wear. These findings offer new contributions to the understanding of the material properties of flints applicable to drillability prediction, tool wear evaluation and drilling/tunnelling system specifications in chalk with flints.

A limited number of lacustrine basins in western Turkey contain world class borate reserves, with mineralisation present as strata bound deposits in Neogene volcano-sedimentary successions. This study examined in detail the relationship between magmatism and borate mineralisation in two of these basins (Ernet and Kirka). The magmatism comprised an Early Miocene K-rich acid phase, represented by granite, ignimbrite, rhyolite and dacite, and a more mafic K-rich, Middle - Late Miocene phase, represented by shoshonite and latite. Information from field observations, mineralogy, isotopic dates, immobile element concentrations and biotite compositions indicate that acid magmatism in Ernet and Kirka Basins was closely related in both space and time to the deposition of the borate-host sediments, whilst mafic volcanism occurred later. The mineralogical and geochemical composition of the borate-host sediments was strongly influenced by the post-depositional modification of rhyolitic, ignimbritic and granitic-derived material in a saline, alkaline environment. The result of the interaction between saline, alkaline waters and dominantly acid igneous products, was the generation of an authigenic mineral assemblage comprising mainly calcite, dolomite, borate, trioctahedral smectite and K-feldspar. Trioctahedral smectite, dolomite and K-feldspar, together with elevated concentrations of As, Sr and Li, correlate particularly well with borate mineralisation. The geochemistry of the Early Miocene acid igneous rocks suggests that acid magmatism represented a likely source for B and Li, and probably also for As and Sr. Possible mechanisms for the transfer of B and other elements from an igneous source to the basin sediments include; transfer by igneous-driven geothermal fluids, rich in B as a result of hydrothermal leaching and contributions from magmatic waters and gases, and the breakdown of igneous material in saline, alkaline lakes. Trace element and Nd and Sr isotropic data indicate that the ultimate source of the B was assimilated upper continental crust, perhaps with some component of melted lithospheric mantle. Comparison with other borate provinces shows a common tectonic setting, characterised by former convergence with associated subduction and crustal thickening.

The massive Fe- and Cu-sulphide mineralisation is the most valuable economic resource in the Troodos and has been explored and exploited mainly through exploratory drilling around ancient slags, gossans and old workings. The exhaustion of these superficial guides has meant a shift to locating orebodies at depth. Direct detection of orebodies by traditional geophysical methods has been difficult. Structures parallel and perpendicular to the spreading axes in the region are thought to control the localisation of the sulphide deposits. Their identification should aid indirect detection of mineralisations. Prior to speculation on possible geological meanings of data from an area not known for sulphide mineralisation, 33 MT and 48 TEM soundings were performed at Klirou, a known area of buried massive sulphide mineralisation. The joint MT/TEM methods identified the low resistivity lithological unit that hosts the mineralisation and the bounding faults, demonstrating their usefulness in mapping the lithological units and structures that host and control these mineralisations. Coincident IP and geological or geochemical anomalies could then be used to locate the orebodies. In Ayia Marina area, 37 MT and 68 TEM soundings were undertaken. Some ENE structures corresponding to the western flank of Mitsero graben, where the extrusion of the Troodos sulphide-bearing lavas is envisaged to have taken place, have been confirmed by ground MT/TEM surveys. The occurrence of olivine-bearing rocks north of Ayia Marina and the existence of an andesite plus 2 km north-northwest of Ayia Marina suggest that the interpreted low resistivity zone in the area may correspond to a prospective zone for massive sulphide occurrence.

This thesis presents an experimental investigation of the micromechanical behaviour of non-active clay, both in saturated and unsaturated states. For the case of saturated clays, 1-D compression tests on kaolin saturated with fluids having different dielectric permittivity (air, acetone, and water) and pH (acid and basic aqueous solutions) were performed. Based on the Pore-Size Distribution (PSD) of samples taken on both the virgin and the unloading curves, the electrochemical and mechanical forces controlling inter-particle interaction and the particle configuration along reversible and non-reversible compression paths were inferred. Ultimately, a conceptual micromechanical model was formulated and designed in such a way that it could be potentially implemented in a Discrete Element Model (DEM) for clay geomaterials. To show the capability of the conceptual micromechanical model, an ‘embryonic’ 1-D DEM model was developed. It was shown to be capable of capturing, at a qualitative level, the 1-D response of clay saturated with fluids of different dielectric permittivity. Moving to the unsaturated state, an observation was initially made that the mono-modal PSDs of kaolin in reconstituted and dry states fit quite well the pore-size distribution of the micro-pores and the macro-pores respectively in compacted samples. Based on this observation, an assumption was put forward that macro-pores are filled with air (‘air-saturated’) and micro-pores are filled with water (‘water-saturated’). The comparison of the PSD of samples compacted with water and acetone and the comparison of the PSDs of samples freeze-dried and oven-dried appeared to corroborate such an assumption. A particle-based microstructural conceptual model for unsaturated soils was then formulated. Such a model can explain the evolution of PSD observed at various compaction water contents. Besides, this microstructural conceptual model was proven to be as effective as the traditional aggregate-based microstructural model in interpreting some of the classical responses of unsaturated soils including volumetric collapse upon wetting. A particle-based microstructural model provides an alternative approach to the aggregate-based microstructural model that has (potentially) the advantage of facilitating the formulation of DEM models for unsaturated clays. Another advantage is that the conceptual microstructural model and, hence, any DEM models would remain essentially the same for saturated and unsaturated states. Following the idea that macro-pores are filled with air and micro-pores are filled with water, it was assumed that the response of unsaturated soils can be modelled by considering separately the response of the dry part (air-saturated) and wet part (water-saturated). To model 1-D compression, the void ratio of the dry part was read from the 1-D compression of dry kaolin and the void ratio of the wet part was read from the 1-D compression of the saturated reconstituted kaolin. This approach allowed modelling the water-undrained compression tests in Tarantino & De Col (2008) with excellent accuracy.

The aim of this study is to provide a greater understanding of the resetting processes, which produce the Rb-Sr closure temperature, allowing the production of more relevant models of closure temperature. This study provides information on the scale, mechanism and pathways of transport of species within rocks to understand how chemical exchange during cooling affects the closure temperatures of isotopic systems. To complete these objectives three areas are addressed: a literature review of the processes thought to be involved in defining a closure temperature, microanalytical work, and modelling of results. The samples studied are closed system marbles, implying that any exchange effects can be quantified, as any species lost from one mineral must be balanced by gain in another mineral or minerals. TIMS Rb-Sr suggests the phlogopite closure temperature is higher than that of biotite. This study and previous modelling work of chemical exchange suggest that closure temperatures are partly controlled by the mineral mode and the elemental concentration of species within each mineral. LA-ICP-MS studies of calcite reveal gradients of 87Sr/86Sr, which decrease away from the mica bands present in the samples over a few centimetres. Ion and electron microprobe work suggest that the movement of elements may be in the opposite sense to that of isotopic exchange, but the results from this part of the study are inconclusive. During cooling from peak metamorphism, isotopic and chemical gradients are "frozen" in different minerals. Modelling suggests that exchange occurs by a combination of volume and grain boundary diffusion. 87Sr/86Sr gradients in calcite are used to produce a new method of producing the age of peak metamorphism and the profile shape describes the cooling history. The results of this study imply that exchange within the Rb-Sr system is very complex and the closure temperature process is more complicated than previously thought.

No description available.

The structures and dynamics of intra-salt layers have received limited study in comparison with the external shape of salt structures. Our limited understanding of the behaviour of intra-salt layers generally comes from salt mines, outcrops, analogue, and numerical modelling where the full three-dimensionality of intra-salt layers is barely observed. To understand the internal dynamics of giant salt structures and the response of their intra-salt layers during regional tectonics, this thesis provides detailed interpretation and analysis of intra-salt layers from the Silverpit Basin, in the Southern North Sea Basin, and the Birba Area, in the South Oman Salt Basin. These two locations provide unique natural laboratories where driver mechanisms for salt tectonics are investigated using high-resolution, high-quality three-dimensional (3D) seismic reflection data. The Silverpit Basin is a buckled basin formed during the Mid Eocene to Late Oligocene, while the Birba Basin was affected by massive sediment loading, which generated differential loading from the Early Cambrian to the Late Permian. Differential loading of the basin caused down-building and influenced the growth of diapirs and minibasins, which later led to intense deformation and fragmentation of the intra-salt carbonate stringers. In the Silverpit Basin, regional salt anticlines encapsulated a 23–63 m-thick intra-salt layer known as the Z3 Stringer. Lithologically, the Z3 Stringer is composed of anhydrite, and it represents a strong seismic marker across the Southern North Sea Basin. Relative to regional anticlines and synclines at the Top Salt level, the Z3 Stringer deformed in a ductile manner comparable in geometry and attitude to the regional salt structure. Non-cylindrical stringer folds, which vary from gentle to isoclinal, are related to the intensity of the regional-scale structure, whereby tighter vii stringer folds are observed under well-developed Top Salt anticlines and synclines. Synclines at the Top Salt level include long-wavelength gentle folds. Extreme thinning of the Zechstein by the downward displacement of the Top Salt causes the stringers to extend and finally break laterally in a mode-1 tensile fracture mechanism. This thesis highlights the complexity of intra-salt deformation and forms a good large-scale case study for the analysis of the kinematics and rheology of competent material enclosed within an incompetent medium. Understanding the complexities and attitudes of intra-salt layers and their encasing salt structures has broader implications for regional tectonic history, hydrocarbon prospectivity, and industrial applications.