The Oman ophiolite is the largest and best preserved ophiolite in the world and records a switch from mid-ocean ridge (MOR) to supra-subduction zone (SSZ) setting. This study investigates the geochemical variability of chrome-spinel in the mantle sequence of the poorly known United Arab Emirates (U.A.E.) part of the northern Oman-U.A.E. ophiolite. Extensive field work was carried out and 260 samples collected for petrogenetic studies and geochemical mapping of the U.A.E. mantle. Chrome-spinel geochemistry provides valuable information on bom the residual mantle and on the nature and extent of melt-rock reaction. In particular, it is used to fingerprint the compositions of the magmas that interacted with the mantle lithosphere. This study also develops a new method to analyse gallium in chrome-spinel by Laser Ablation-ICP-MS, and successfully uses it to improve the tectonic discrimination of chrome-spinel. The results show that the U.A.E. mantle lithosphere formed at a MOR-type setting and was modified by melt-rock reaction with MORB-type and SSZ-type melts. This history of melt infiltration strongly resembles the magmatic history of the crustal sequence in each of the Aswad and Khawr Fakkan Blocks. Geochemical mapping illustrates a strong spatial control on the pattern of melt infiltration in the mantle and constrains the proximity of each mantle domain with respect to the subduction zone. The Khawr Fakkan mantle extensively interacted with boninitic melts during subduction initiation. Thus, it was closer to the subduction zone than the Aswad mantle which predominantly interacted with island-arc tholeiite melts. Importantly, this work demonstrates for the first time that the Dibba Zone peridotites originate from pre-existing 'true' MOR mantle lithosphere between the trench and the main body of the ophiolite. A further important conclusion is that the mantle lithosphere of the northern Oman-U.A.E. ophiolite was not the source region for the SSZ magmatism. Previous workers proposed that the plane of detachment and the subduction zone were the same, which implies that the mantle of the ophiolite was the source of the SSZ magmatism. Instead, this study proposes that detachment of the ophiolite took place at a shallower level than the plane of the subduction zone and thus provides strong evidence for a subduction zone at a still deeper level. During detachment, the ophiolite incorporated slices of ultramafic rock near the trench (i.e. the Dibba Zone peridotites) as it bulldozed its way over the underlying plate and onto the continental margin of Arabia.

This project reports results of a hydro-geochemical study of leachate production at the Silent Valley landfill, Blaenau Gwent, South Wales, UK. Silent Valley landfill site is an active unlined landfill in South Wales. It lies on interbedded sandstones and mudstones of the Rhondda Beds, which are overlain by a mixture of boulder clay, head deposits and made ground. The annual rainfall recorded in the area is approximately 1250 mm. Resistivity surveys were performed across part of the site to help improve the understanding of the internal structure of the landfill. Instrumentation to measure leachate discharge, conductivity and meteorological inputs installed at the Silent Valley landfill site are described and relationships between the rainfall and discharge data are analysed. Regression analysis is used to model the discharge of leachate from the measured meteorological data. Water balance analysis has demonstrated that groundwater is entering the site. The leachate generated on site is collected by a series of drains that feed into the Settlement Tank, which then discharges to foul sewer. The discharge through the Settlement Tank shows a rapid response to rainfall events with dilution effects indicated by conductivity readings and chemical analysis. The volume of discharge from the Settlement Tank is shown to have a long-term upward trend. A preliminary study was undertaken to investigate the use of neural networks to model the discharge in the Settlement Tank. Feedforward backpropogation neural networks were constructed using the measured meteorological data to produce predictions of daily discharge for the Settlement Tank. Ion Chromatography analysis was performed on the leachate to complement the historical leachate analysis data. Element concentration was correlated with conductivity data and variations related to discharge measurements. Since monitoring began in 1993, many of the leachate constituents have shown an increase in concentration.

The Magmatic Evolution and Crustal Accretion of the northern Oman-U.A.E. ophiolite The Oman-United Arab Emirates (U. A.E.) ophiolite is the largest and best-preserved ophiolite complex in the world and has assumed critical importance in guiding ideas as to the functioning of mid-ocean ridge magma chambers and accretion of lower crust formed at a fast-spreading ridge. The portion of the ophiolite within the United Arab Emirates has received much less study than that within the Sultanate of Oman, particularly with regard to its magmatic evolution. Fieldwork has been conducted in co-operation with the British Geological Survey on the ophiolite sections in the U.A.E. Geochemical and field characteristics of these plutonic and extrusive units provide important constraints on the influence subduction-related fluids have on crustal accretion processes. Initial VI magmatic events exhibit a MORB-like composition and record mid-ocean ridge accretion processes which relate to modern crust, forming from steady-state magma chambers. The Khawr Fakkan Block provides the first 'true' MORB mantle source signature to be documented in the Oman-U.A.E. ophiolite, which represents pre-subduction zone influenced oceanic crust and applies constraints to the mechanisms and timing of subduction initiation and propagation. These primary events were followed by V2 magmatic events in a supra subduction zone (SSZ) setting, with plutonic magmatism localised predominantly along major faults. Each subsequent magmatic event exhibits an increase in the subduction related component to the mantle source. The V2, SSZ, magmatic period of the northern Oman-U.A.E. ophiolite can be regarded as an embryonic volcanic arc, which ceased magmatism and was obducted before reaching maturity. The northern Oman-U.A.E. ophiolite records the transition from spreading- to subduction-related volcanism in a SSZ setting within a marginal (fore-arc) basin, representing the change from steady-state to plutonic magmatism. The SSZ signature increases to the north spatially and temporally.

This thesis comprises three studies which utilise detailed micro-sampling techniques to understand the effects of melt infiltration in the continental lithosphere and the relationship of deeply derived kimberlite melts to lithospheric processes. To be able to make these links it is necessary to better constrain the geochemical composition of the primary kimberlite melt. • The first study investigates inter-grain trace element and Sr isotope variation in clinopyroxene (cpx), amphibole and melt from two spinel lherzolite xenoliths from the Middle Atlas Mountains, Morocco. These results support a multi-stage metasomatic process in which cpx and amphibole are recent additions to the lithospheric mantle, most recently equilibrated with a carbonatite melt. The limited Sr isotope variation in the cpx from this study is typical of global off-craton cpx implying that the majority of cpx in off-craton settings may have a recent, metasomatic origin. • The second micro-sampling study examines inter-grain trace element and Sr isotope variation in garnet and cpx in garnet lherzolite xenoliths within cratonic peridotites from Bultfontein, South Africa, and Pyramidfels, Greenland. The Sr isotope and trace element variation, combined with a lack of trace element equilibrium between cpx and garnet, imply that the majority of cpx is a recent addition, associated with the host kimberlite-type magma, whereas the garnet is added by an older event, probably by a melt related to either Group II kimberlite or lamproite. A global database of Sr and Nd isotope data for cpx and garnet indicates that these conclusions can be applied more widely. The metasomatic addition of cpx and garnet is limited to vein-wallrock reactions and therefore the majority of lithospheric mantle is concluded to be depleted harzburgite or dunite. • The third micro-sampling study focuses on constraining the primary geochemical characteristics of kimberlite magma by analysing the constituent phases (perovskite, olivine, apatite, phlogopite, calcite) for trace element and Sr isotope ratios from a sample of hypabyssal kimberlite from Jos, Somerset Island, Canada. An analogue study was carried out on an olivine melilitite from Saltpetre Kop, South Africa with a similar mineral suite (with the addition of melilite). These results show that phenocrystal olivine and apatite provide the best record of the source Sr isotope composition whereas perovskite, typically analysed by laser ablation, is more variable and influenced by crustal interaction, albeit to a limited extent. The results indicate that previously recorded differences between the Sr isotope compositions of whole rock kimberlites and the low-Cr megacryst suite, used to rule out a genetic relationship between the two, can be ascribed to later stage crustal interaction with the kimberlite. As a result, the link between kimberlites and the formation of the low-Cr megacryst suite is strengthened.

The literature on the determination of fluoride is reviewed. Attention Is given to its analysis in silicate materials, especially rocks and minerals; developments in method are traced from the first work, published in 1816, to the present. Special emphasis is given for the period 1951 through 1959, Important methods and other pertinent work and findings being summarized chronologically by subject and without regard to systematic exposition of contradictions or their explanation: The summaries of some work are nevertheless detailed enough to make manifest some contradictions. Conflicting findings on the precision in the visual thorium titration and on the visual ratings of various Indicators for this titration are thought merely to reflect Individual skill and choice rather than superiority of method and (or) indicator. A strong case is thereby made for Instrumental methods of analysis. A method developed to determine fluoride in metamorphic rocks Is described. A sodium peroxide decomposition, followed by a precipitation of silica and alumina and a steam distillation of the filtrates, gave quantitative isolation of fluoride. Aliquot8 of distillate were titrated spectrephotometric ally in perchloric acid-sodium sulfanilate buffered solution in the presence of sodium 2-(p-sulfophenylazo)-1,8-dlbydroxy- naphthalene-3,6-dlsulfonate (SPADNS). The method was tested with synthetic rocks and soda feldspar, to which known amounts, ) of fluoride were added. Aliquots were titrated spectrephoto metrically to within one microgram of fluoride. Results with G-l and w-1 are compared with analyses reported by others. Replicate results for ten raetamorphic rocks indicate a maximum proportional deviation of 2.0 percent. However, further replications have shown the error is somewhat greater, although nevertheless favorable: The standard deviation for 122 replicate determinations is +0.0014. percent fluoride for rocks having up to 0.09 percent fluoride. The applicability of the perchloric acid-sodium sulfanilate buffer for the thorium titration is examined. It is felt it is superior to the monochloracetlc acid buffer commonly used. The results of an Interlaboratory standardization program conducted to check the validity of several methods and the comparability of results and to suggest possible superior methods of analysis are presented. Agreement is not favorable when all results are compared; possible matrix effects for pyrolltic and chemical methods are considered. Four of the eight procedures employed show favorable agreement, aspects of which are studied. Work, carried out on synthetic solutions containing the elements commonly analyzed in the "main portion" of silicate rock analysis, is given and discussed. Minor modifications, mainly in technique, of the generally accepted methods are detailed. An important improvement in the examination of the calcium oxide and magnesium pyrophosphate precipitates for impurities such as strontium in the former and calcium and manganese In the latter has been developed. Considerable attention Is given to the problem of determining "blanks" for this part of silicate rock analysis.

Constraining the formation age of platinum-group minerals (PGM) in placer deposits has traditionally been very challenging. The 190Pt-186Os decay system, measured by laser ablation multi-collector ICPMS (LA-MC-ICPMS), has been demonstrated as a useful geochronometric tool for detrital PGM grains. However, it is difficult to appraise the method accuracy using detrital PGM. In this thesis two examples are presented that verify the accuracy and precision of the technique in geologically well constrained situations. The age of the Bushveld Complex has been measured using various radioisotope chronometers which yield ages ranging from 1921 – 2165 Ma, although an age of 2054 Ma is widely accepted. We present an accurate isochron age of 2012 ± 47 Ma (2σ, n = 50, MSWD = 1.19) for in situ Bushveld PGM, demonstrating the validity of multi-grain Pt-Os ages. Precision on the Bushveld LA-MC-ICPMS Pt-Os age is comparable to the Re-Os and Rb-Sr ages but data acquisition is easier and less time consuming. Scatter on the isochron may result from analytical artefacts or from post-crystallisation disturbance of the Pt-Os system within Pt-rich PGM grains via exsolution or deformation followed by incomplete sampling of the resulting within-grain heterogeneities. Placer PGM derived from the Meratus ophiolite, southeast Borneo yield a precise Pt-Os isochron age of 197.8 ± 8.1 Ma (2σ, n = 260, MSWD = 0.90). This is consistent with published age constraints and provides the first direct date for the igneous rocks of the Meratus ophiolite, highlighting the utility of the Pt-Os geochronometer as a tool for dating ophiolites, layered intrusions and placer platinum mineralisation despite potential derivation of PGM from various isolated chromitites. Analysis of large PGM populations has allowed improvement on published constraints for Pt/Os inter-element fractionation occurring during ablation analysis of PGE sulphides and alloys. This is estimated to amount to between 2 – 2.5 %.

The peat soils found in blanket bogs are significant stores of carbon. The degree to which these ecosystems are currently functioning as sinks or sources of carbon is not clear. There is a paucity of measurements from suitable sites but the available evidence suggests that certain sites might be close to being carbon neutral or acting as a net source of carbon to the atmosphere. A complete understanding of the carbon budget of a landscape requires a comprehensive assessment of the magnitude of the whole range of pathways by which carbon enters and leaves the system. Measurements were made of all of the key gaseous carbon fluxes, including the net CO2 flux, the soil CO2 flux and emissions as methane. A flux partitioning model was utilised to separate the net CO2 flux into its component parts. Values for the fluvial carbon losses from the site were taken from the literature. The various CO2 fluxes were by far the largest terms in the complete carbon budget. Growing season measurements showed that methane emissions were a small component. The key environmental variables that were driving the temporal variations in the fluxes were identified. In general soil temperature was important in explaining variations in ecosystem respiration, soil CO2 fluxes and the methane flux. The water table was usually high and fluctuations did not appear to affect carbon fluxes. There was evidence of increased soil CO2 fluxes as a response to low soil moisture levels during a summer dry period. A comprehensive carbon budget for the blanket bog at Moor House NNR showed the site to be a relatively large carbon sink, of an estimated 134.09 ± 32 g C m-2 yr-1.

The Sunda island arc of Indonesia formed as a result of the northward subduction of the Indo- Australian Plate beneath the Eurasian Plate. Along-arc variations in the composition and thickness of the overriding Eurasian plate and variation in the type and amount of sediment deposited on the subducting plate create differential effects on Sunda arc lava geochemistry. Detailed study of volcanic rocks from Salak, Gede Volcanic Complex (GVC) in West Java and Ijen Volcanic Complex (IVC) in East Java was carried out in order to establish the relative importance and contributions of various potential source components and composition-modifying processes at individual volcanic centres, prior to investigating petrogenetic variation along the arc. Differentiation processes play a major role in modifying the geochemical composition of Sunda arc magmas. However, the relative importance and traceable impact of the different processes varies at each volcanic centre. Fractional crystallisation of a typical Javan island arc mineral assemblage exerts the largest control on major and trace element composition of the volcanic rocks. Distinct intra-volcanic complex differentiation trends at rvc and Salak are spatially controlled and are explained by independent conduits and multiple magma reservoirs at different depths in the crust - linked to sub-volcanic structure. Shallow level contamination by typical upper-crustal continental material is insignificant during magmatic differentiation at Salak, GVC and IVC. However, at Salak there is some evidence for assimilation of material similar in composition to the volcanic rocks. Deep fractionation of a phase in which HFSE and HREE are compatible (e.g. amphibole) is inferred in the evolution of most Javan magmas. Magmatism at Salak, GVC and IVC is the product of shallow, relatively homogeneous, fertile, Indian Ocean MORB-like mantle that has been enriched by slab- derived component(s) sourced from the altered oceanic crust and subducted sediment. Hf and Nd isotope ratios of Javan lavas show that the subducted sedimentary source component is heterogeneous and reflects spatial variations in sediment compositions on the down-going plate along the Java Trench. A progressive eastward increase in Sr isotope ratio of volcanic rocks across West and Central Java broadly correlates with inferred lithospheric thickness. A significant change in crustal architecture (i.e. thickness) occurs between Central and East Java. This transition may represent the south-eastern boundary of Sundaland (pre-Tertiary arc basement).

The Magnesian Limestone is of Permian age. In Durham, shelf and basin fades can be recognized within the Lower division while lagoon, reef and basin facies occur within the Middle division. Calcite, dolomite, gypsum and anhydrite form the main mineralogical components, although minor amounts of limonite, quartz, pyrite and an illitic clay mineral are common. Gypsum and anhydrite are characteristic of the two basin facies but are also associated with the shelf and lagoon facies in South-East Durham. In North-East Durham, the three shallow-water facies are predominantly dolomitic; calcite occurs most commonly as void filling, but also replaces dolomite and occurs in a "felted" texture which is believed to have been formed by replacement of a sulphate mineral. Extremes of carbonate composition are found within the two basin facies. Sulphates only occur in abundance where dolomite is the predominant carbonate. Calcite is believed to have formed at depth by the reaction of dolomite with locally derived, sulphate- rich solutions. The process might still be occurring. Differences in pore-size distribution make the shallow-water facies more porous and permeable than the basin facies. The relationship between porosity and permeability is discussed. Strontium occurs as a solid-solution impurity in dolomite and calcite and, to a much greater extent in gypsum and anhydrite. Dolomite also contains considerable manganese. During dedolomitization by the "sulphate-agent" mechanism, strontium is incorporated into, and manganese largely excluded from, the lattice of the replacement calcite. Rubidium and at least some barium, lead, boron and nickel are considered to occur as detrital constituents within the illitic clay material. Copper, in part at least, is associated with organic carbon. Zinc, lead and barium are enriched in rocks of the three shallow-water facies. The elements are considered to have been introduced into porous and permeable rocks by metal-bearing solutions. The mode of occurrence of these elements and the source of the "mineralizing" solutions is discussed.

The palaeogeographic, tectonic, and biologic conditions of seatearth deposition are briefly reviewed. Detailed mineralogical examination reveals that seatearths are essentially quartz-illite-kaolinite assemblages with minor chlorite, siderite, and organic matter. The illites show wide variation from well ordered sedimentary muscovites to disordered and/or interlayered 'illitic' minerals. The kaolinites are found to be relatively well crystalline and the chlorites are Mg rich. Siderite is commonly associated with minor kaolinite and pyrite in nodules. The organic matter consists of terrestial plant debris. The distribution functions of elements and minerals in seatearths are discussed, A normal model is reasonably satisfactory for SiO(_2), Al(_2)O(_3), CaO, P(_2)O(_5), Ni, Y, and Zr; a lognormal model for TiO(_2), Fe(_2)O(_3), MgO, Na(_2)O, K(_2)O, S, C, H(_2)O(^+), H(_2)O(^-), CO(_2), Ba, Or, Ou, La, Mn, Nb, Rb, Se, Sr, and Zn. Stepwise multiple linear regression is used to assess the relationships between chemistry and mineralogy. It is found that the major components are controlled by the mineralogy to a large extent and that the trace elements and similarly controlled but to a lesser degree. The present data, when compared with previous data, is shown to be comparable .R-mode factor analysis is used to derive factors which control the distributions of trace elements and minerals in seatearths. Eight factors are extracted and they relate to the depositional environment and stratigraphic controls. Roof rocks are examined and the pattern they produce after R-mode factor analysis is shown to be similar to that for a set of clastic cyclothemic sediments. The significance of differences between seatearths and roof rocks are discussed. It is concluded that seatearths are leached relative to their corresponding roof measures. The data is summarised and a detailed theory for the origin and genesis of seatearths, based on that of MOORE (1968), is developed.