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This thesis presents the results of an investigation into the non-equilibrium distribution of trace constituents as a function of crystal growth. The ultrabasic igneous complex of Rhum (Scotland) with its relative uniformity of mineral composition, but variety of mineral habits was used in the investigation. For this, the distributions of elements of contrasting behaviour have been studied, and especially uranium which strongly partitions into the melt, and strontium, which partitions into the feldspar on fractional crystallisation of a basaltic magma. The technique of fission track analysis for uranium is fully described, and further developments have been introduced in order to accurately map the inter- and intra-mineral uranium distributions in polished rock sections. Results of uranium, strontium, nickel and calcium concentrations in the cumulus phases olivine, clinopyroxene and plagioclase feldspar are given. There is a good correlation between the partition coefficients of uranium and the morphologies of the major cumulus phases. Calculations of crystal growth rates for different olivine morphologies have been determined. On these observations, a model is proposed relating both the mode and variation in nucleation rates of the individual morphologies to the degree of supercooling of the melt. Data on other elements are presented to substantiate these arguments. It is shown that olivines of spinifex (harristic) type have grown at a relatively fast rate and not slowly as suggested by some workers. The mode of crystallisation of certain morphologies, as to whether by diffusion-controlled growth, or by interface-controlled growth is discussed. The distributions of uranium and other geochemically compatible elements in the intercumulus minerals are described, and the results of reaction of the cumulus with the intercumulus material studied. Zirconolite (or zirkelite) is recorded in a terrestrial basic intrusion for the first time.

The hydrogeochemistry of the southern Lincolnshire Limestone is investigated employing inductively coupled plasma-optical emission spectrometry (ICP-OES) as the primary analytical technique. Two simultaneous, multi-element instruments were used. The principles of the technique and comparisons of the hardware, operating conditions and routine sample preparation methods are outlined and realistic levels of precision and detection limits evaluated. The range of determinations in the groundwaters was extended by the development of novel sample treatment techniques including the determination of dissolved sulphide down to the 1 level using a gas-liquid separator, and the determination of rare earth elements in groundwater evaporation residues. The methods were applied to the analysis of groundwaters and rocks of the Lincolnshire Limestone in southern Lincolnshire. The geology, hydrogeology and hydrochemistry of the aquifer are reviewed and the sample collection methods described, stressing the precautions taken to avoid contamination. The Lincolnshire Limestone is an aquifer of considerable heterogeneity, argillaceous limestones are intercalated with pure oolites and it is confined by predominantly clastic formations. The major element chemistry of the groundwaters follow a down-dip trend between calcium-bicarbonate-sulphate waters near outcrop and saline, non-potable waters in the east. The groundwaters are sub-divided into zones based on the processes of calcite dissolution, ion exchange and the mixing of recharge and saline interstitial waters. Minor and trace element behaviour is controlled by a combination of oxidation-reduction reactions, adsorption on clay minerals and organic matter, mineral solubilities, complex formation andgroundwater pH. Ultimately the low levels of most trace metals are limited by their low abundance in the limestone. Temporal hydrochemical trends are identified, and the influence of man, with reference to the down-gradient migration of agrichemical pollutants (e.g. nitrates) is assessed. Fluctuations in the movement of the potable/saline water interface are noted and theories on the origin of the saline waters reviewed.

Semarkona is an unequilibrated ordinary chondrite which has experienced the least amount of thermal metamorphism and has the highest whole-rock D/H ratio of the ordinary chondrites. It is also unusual in that it has undergone some mild aqueous alteration, previously considered a secondary process restricted to some deuterium-rich carbonaceous chondrites. Semarkona was chosen to be the object of a more detailed study of secondary alteration and to determine whether the deuterium-rich phase was related in any way to the aqueous alteration process. A procedure was developed involving three analytical techniques (chemical/petrographic, thermoluminescence and hydrogen isotope) to study individual fragments of this meteorite. The deuterium-rich phase was found to be concentrated in the chondrules, average SD = +3890%o, with a maximum measured 3D of +7500%o in one of the chondrules. The matrix had a moderate deuterium enrichment, of average 3D = +2670%o. The isotope results in conjunction with the other techniques employed indicated that the chondrules that had experienced aqueous alteration are deuterium-rich. The water involved in the aqueous alteration was either deuterium-rich or transported deuterium-rich organics to the sites of aqueous alteration. In order to reduce sample size requirements, it was necessary to develop an inlet and mass spectrometer system capable of the isotopic analysis of less than O. 1 tmol hydrogen. Two inlet systems were developed for use with a dynamic mass spectrometer and compared with a conventional inlet system. The inlet system with greatest sensitivity, capable of analysing 0. lpmol hydrogen, was used for the isotopic study of Semarkona; however, the accuracy of this system was poor due to the presence of a memory effect. Experiments, using the conventional inlet, showed that this memory effect was due to sample water remaining on the surfaces of the inlet system. The presence of the memory effect could not be eliminated, but a correction procedure was obtained. These experiments have shown various methods in which the memory effect can be overcome by careful design of an inlet system. Finally a static mass spectrometer system was developed, capable of analysing less than lnmol hydrogen, in the form of methane. Initial results show that this system is capable of the isotopic analysis 0.01 μmol of water with SD in the range of -500%o to +5000%o to an accuracy of ±20%o.

Isotope, major and trace element studies of the Late Cretaceous and Tertiary granitoids of the Atlanta lobe of the Idaho batholith in the western United States cordillera have led to new. insights on the nature of the lower crust and have placed constraints on granitoid magma genesis during a transition from a compressional to an extensional regime. The Cretaceous (-90-75Ma), calc-alkaline, tonalitic to granitic, ' metaluminous to peraluminous granitoids are characterised by high LILE/HFSE and LREE/HREE ratios, low Rb/Sr and Snx/Ndr atios and F-Nda nd ESro f -4.9 to -11.6 and 35 to 120 respectively. Only the tonalites and silicic granodiorites to granites underwent significant degrees of within suite fractional crystallization, the former dominated by hornblende and plagioclase and the latter by alkali feldspar, quartz, plagioclase and biotite. The Cretaceous magmas have been successfully modelled as 25%-45% partial melts of tonalitic to gabbroic, biotite, garnet and homblende-bearing meta-igneous*s ources. Thermal conditions suggestt hat anatexis was induced by both Sevier tectonic crustal thickening and ponding of subduction-relatodb asalts at the base of the crust. The inferred source regions were relatively trace element enriched, with high Sr and LlLE/HFSE ratios; this volcanic-arc signature was presumably attained during generation of the source region by subduction related processes. Little intra-crustal reprocessing of the source region can have occurred, but unsupported Sr and Pb isotope ratios suggest that minor depletion of Rb, U, and Th by high-grade metamorphism may have occurred. Small differences between the trace element compositions of the Cretaceous intrusive phases are thought to reflect minor heterogeneitiqs within the source regions. Small volume leucogranites with distintive REE and isotope compositions are interpreted as upper crustal, partial melts of Archaean and Proterozoic metasediments. Inferred garnet-bearing granulitic residues after partial melting cause Sm/Nd ratios to be significantly reduced from source to magma, but correcting for this produces TLM in agreement with Pb-Pb ages of -1.5Ga. This mid-Proterozoic age of the lower crust indicates that major age province boundaries with the Wyoming and Snake River Plain Archaean provinces exist to the east and close to the southern margin of the Atlanta lobe. The Tertiary bimodal granitoids consist of a 55Ma-47Ma, metaluminous dioritic suite characterised by high Sr and Ba, low LILE and moderate LREE/HREE ratios, and a 48Ma- 42Ma, peraluminous granitic suite are characterised by lower Ba and Sr abundances and LREE/HREE ratios, higher HFSE and Rb, U and Th abundancesw, ith large LILE variation and minor to large negative Eu/Eu* anomalies. F-Nd and ESr of -4 to - 11.8 and 25 to 65 respectively, in the dioritic suite, systematically vary with major and trace elements and are interpreted to reflect AFC processes, with dioritic initial magmas derived from the subcontinental mantle lithosphere and high proportions of old continental crust assimilants. The Tertiary granitic suite have higher ESr and lower ENd and Pb isotope ratios than the Cretaceousg ranitoids, but NU similar mid-Proterozoic T6M. They are modelled as anatectic melts at the base of a thinned, isotopically distinct region of a trace element enriched lower crust similar to the source of the Cretaceous granitoids to leave a mafic granulitic residue without garnet leading to distinctly higher Y and Yb abundancesin the Tertiary granitoids. The Cretaceous to Tertiary transition from lower crustal granitoids generatedin a tectonically thickened crust with ponding of subduction-related basalts, to generation of granitoids in an attenuated lithosphere, due to rapid uplift, themial and gravitational relaxation and extension in the latest Cretaceous, is reflected in the change to increasing HREE abundances, the incorporation of mantle-derived material and the epizonal levels of emplacement and association with the coeval Challis volcanics.

The geochemistry and temporal evolution of small volume potassium-rich mafic volcanics within the non-extensional, uplifted central Colorado Plateau and Sierra Nevada have been studied in detail and a general model is proposed for non-extensional, uplift-related, magmatism within the Western Cordillera. The Oligo-Miocene potassic-ultrapotassic lamprophyres of the Navajo Volcanic Field, Colorado Plateau, and the late Miocene-Pliocene shoshonites of the San Joaquin- Kings Volcanic Field, Sierra Nevada, represent primary or near primary mantle-derived melts that have experienced limited crystal fractionation and/or crustal contamination. Yet despite this each suite of samples is characterised by a significant range of trace element and isotope ratios. The variation in LIL/HFS ratios (Ba/Nb=11-77) and isotopic ratios (87Sr/86Sr=0.7044-0.7071) of the Navajo lamprophyres are attributed to small degrees of melting of a compositionally and mineralogically heterogeneous lithospheric mantle source. By contrast a similar, though slightly more extreme, variation in trace element and isotope ratios of shoshonites from the Sierra Nevada (Ba/Nb=70-325,87Sr/86Sr=0.7050-0.7069) are attributed to mixing of magmas derived from incompatible element enriched lithospheric mantle and depleted asthenospheric mantle. Despite the differences in petrogenetic model for the magmatism within the each study area, the magmatic evolution of both the Colorado Plateau as a whole and the Sierra Nevada are similar. Initial magmatism within each province is dominated by a comparatively long history of incompatible element-enriched lithosphere-derived potassic magmatism. After a period of volcanic quiescence, lasting approximately 11 and 5Ma within the Colorado Plateau and Sierra Nevada respectively, the final, relatively short period of volcanism is characterised by compositions more typical of asthenosphere-derived magmas. New Ar-Ar agesf or the Navajo lamprophyresa nd existing K-Ar agesf or the Sierran shoshonites suggest that the onset of lithosphere-dominated magmatism within both the central Colorado Plateau and Sierra Nevada was coeval with the onset of major uplift during the late Cenozoic. The temporal evolution of magmatism and the degree of uplift, combined with geophysical and xenolith evidence, are consistent with a model in which uplift and preextensional magmatism of the Colorado plateau and Sierra Nevada resulted from the convective removal of the lower lithosphere. In the case of the Colorado Plateau convective thinning of the lithosphere is in response to its previous thickening during the Laramide orogeny whereas in the Sierra Nevada it is related to the cessation of subduction and the development of the San Andreas transform margin during the late Cenozoic. Uplift resulting from convective thinning of the lithosphere increases the gravitational potential of the orogen and the likelihood for later collapse and provides an explanation for the close temporal relationship of mafic mantle-derived magmatism, uplift and major crustal extension typical of the Western Cordillera of the United States.

An assessment of stepped heating procedures for the extraction and isolation of carbonaceous species from fluid inclusions resulted in the development of low-blank procedures which permitted Sl3C characterisation of palreofluid CO2 (down to nanomole quantities) with an accuracy approaching that of the corresponding analytical precision. Similar procedures were successfully applied to the ol5N measurement of palreofluid nitrogen at the sub-nanomole level. An investigation into the origin of fluids which characterised the earliest episodes of palreohydrothermal activity associated with the granites of S W England indicates that the abundance of trace carbon species (C02 , CH4 ) and nitrogen in the fluids was correlated with the metasedimentary contribution to the respective granite source. Furthermore, SiSN and ol3C data (obtained on fluid components and local Palreozoic metasediments, in conjunction with published ol5N values of Cornubian granites), indicate that carbon and nitrogen in the hydrothermal systems were derived from the granite magmas. The chemical composition of the early hydrothermal fluids, together with geochemical and isotopic constraints from the characterisation of Palreozoic metasedimentary country rocks, support the view that the fluids were genetically associated with the granites. Fluid interaction with the local metasedimentary rocks at a high level crustal appears to have been very limited. The incorporation of sedimentary matter into granitic protoliths during anatexis, with subsequent transfer to an exsolved hydrous phase during pluton cooling, is the most probable route by which palreofluid solutes entered the early hydrothermal systems. Hydrogen stable isotope data, measured on the extracted palreowaters, indicate that meteoric water was not a significant component of early hydrothermal systems associated with either the Dartmoor granite or the nearby Hemerdon Ball intrusive, if sub-solidus isotopic exchange was significant. In contrast, comparable data from early fluids associated with other component intrusives of the batholith (as characterised by W ± Sn oxide paragenesis) are consistent with the progressive dilution of a magmatic-hydrothermal component by local groundwaters.

<p> In the southern White Pine Range (SWPR) silica is found to have been deposited from hydrothermal solution within the Currant Gap Detachment fault (CGD). Silica has been observed to occur in three modes of deposition: (1) narrow veins within the lower plate Pole Canyon limestone, (2) bulk silicification of carbonates and (3) breccia matrix found in proximity to the CGD. </p><p> Through stable isotope analysis of oxygen from quartz samples and hydrogen from fluid inclusions we see that there is a history of meteoric waters penetrating into the Lower Pole Canyon Formation, in the lower plate of the CGD. This study reveals that silica in the SWPR formed from aqueous fluids at temperatures between 260 &deg;C and 315 &deg;C within lower plate quartz veins and 150 &deg;C to 300 &deg;C within the upper plate of the CGD. These temperature ranges are in line with what would be expected in a brittle regime (T &lt; 350 &deg;C).</p><p>

<p> Quantifying recharge in arid watersheds, such as the Indian Wells Valley, CA, is critical for a reliable assessment of groundwater availability. In this study, lumped parameter models were coupled with tritium, radiocarbon, and helium data to generate groundwater ages. These ages were paired with (1) noble gas temperatures (NGTs) data to evaluate paleotemperature trends, and (2) well and aquifer parameters to calculate groundwater recharge rates. Age trends of NGTs reveal a complex climatic evolution within the Indian Wells Valley. Exponential trends between the point scale groundwater recharge rates and distance between the well and the mountain fronts of the basin translate to a mean mountain front recharge rate of 9.92 millimeters per year. These trends may be applicable in other arid settings where a lack of point scale data prevents a reliable estimation of recharge.</p><p>

The two main aims of this study were; (i) to determine the equilibrium fractionation effects of the stable isotopes of carbon between dissolved molecular CO2 (C02(aq) ) and bicarbonate (HC03-) (Eb/a ) and HC03 - and carbonate (CO/-) (Eclb ) in sea water, and (ii) to investigate the relationship between the isotopic composition of phytoplankton (013CpOC) and their photosynthetic source of inorganic carbon. To determine Eb/a and Eclb in sea water (S = -34) experiments were conducted at different pHs and two temperatures (SOC and 20°C). The measured values of Eb/a (SOC = 11.67 ± 0.34 %0 and 20°C = 9.48 ± 0.26 %0) agreed well with previous estimates derived in distilled water indicating Ebla is not modified by the ionic effects of sea water. The values of Ec/b determined during the same experiments were significantly larger than previous estimates (SOC = -8.1 ± 2.2 %0 and 20°C = -14.2 ± 2.4 %0). This may indicate that the measurement made during this study are in error. It is suggested that the error is either due to the relative imprecision associated with the determination of the isotopic composition of the total dissolved inorganic carbon pool or due to incomplete isotopic equilibrium within the experimental system. The relationship between changes in the o13Croc and the dissolved inorganic carbon pool was investigated during temporal studies of phytoplankton blooms in a mesocosm and the Menai Strait, North Wales. During the mesocosm experiment the isotopic enrichment between the phytoplankton and CO2(aq) (EPOC/a ) decreased from -- -10 %0 to - +0 %0 during the course of the bloom. The observed changes in 013CpOC are generally consistent with previously published empirical models which assume CO2(aq) is the exclusive source of photosynthetic inorganic carbon. This agreement, and the application of physiological models appeared to confirm that CO2(aq) is the most likely source of photosynthetic inorganic carbon. The o13Croc results obtained during two consecutive phytoplankton blooms in the Menai Strait, North Wales, were corrected for the presence of refractory organic matter to obtain the isotopic signal associated with the phytoplankton, 013Cp. It was apparent that the relationship between 013Cp and [C02(aq)] differed between the two blooms. During the first bloom ( diatomaceous), the observed relationship between 013Cp and [C02(aq)] was consistent with the uptake of CO2(aq). However, the 013Cp signal during the second bloom, dominated by Phaeocystis, was independent of the [C02(aq)J and therefore it was concluded that HC03- is the most likely source of inorganic carbon.