Thèse 3e cycle--Géologie structurale--Paris VII, 1981. / Notes bibliogr.

Th.--Sci. nat.--Brest, 1977. / Rés.

Th.--Sci. nat.--Nancy--I.N.P.L., 1979.

The origin of the dark microdioritic inclusions within I-type granitoids has been the subject of much debate and speculation. These 'xenoliths' have been variously ascribed to restite or cognate crystallisation (autoliths), wall rocks (accidental xenoliths), exotic (mantle) magmas and immiscible liquids. The object of this study was to test between these potential sources of inclusions and processes and to investigate whether such inclusions can be used to provide information on the petrogenesis of the host pluton and the nature of the source region(s) as well as processes of compositional zoning. The approach used was to study inclusions and their host rocks from three zoned plutons in the Caledonian of Scotland, namely Strontian, Ballachulish and Criffell. These were investigated petrographically, by whole rock major and trace element analysis and by Sr and Nd isotopes. Interpretation of the equilibration between inclusion and host benefitted from theoretical considerations of diffusion. It was found that for most 'igneous' inclusions Sr isotopes had thoroughly equilibrated, hosts and inclusions normally having identical Sr initial ratios. However the microdioritic inclusions normally retain a more primitive signature in their Nd isotopes (normally up to +2 Nd units greater than the host) precluding cognate, restite or immiscibility origins and are quite different from local country rocks. Most 'igneous' inclusions thus appear to have an exotic source of more primitive composition, presumably the upper mantle. The appinites of the Strontian pluton were also investigated as part of a study of coexisting acid-basic melts in granitoid plutons. It is shown that these appinites have quenched liquid contacts with the granitoid hosts and some degree of mixing between appinitic magma and host granitoid has given rise to a reverse zonation pattern in composition and texture. The isotopic data for the appinites of Strontian and for inclusions and their host granitoids in the Strontian and Criffell plutons point to a model for the initiation of granitoid magma genesis in the crust by advection of heat through transfer of basaltic magma from the upper mantle. Some of this magma is incorporated in the granitoid magma as basaltic inclusions which gradually become modified towards dioritic compositions. The characteristics of this mantle derived magma and the granitoid crustal source do not vary significantly between Strontian and Criffell in terms of Nd isotope model ages. This is a remarkable finding considering the very different tectonic settings and suggests greater similarities at deeper lithospheric levels. The study of Nd isotopes in xenolithic inclusions in granitoids has been shown to provide at least as much additional information on the petrogenesis of granitoid plutons as the conventional study of their host rocks, but a complementary study of Sr isotopes is not particularly useful. This investigation provides some of the theoretical basis for this and presents a methodology for carrying out such investigations.

Radiometric, whole rock trace element and petrological studies are reported for two late Caledonian granite complexes from the Grampian Highlands, Scotland. These studies throw light on the magmatic history of the intrusions and. more particularly. on their radioelement geochemistry and heat production which is interpreted in a geothermal context. The Etive Complex is a multiphase intrusion, ranging from diorite to granite in composition, emplaced by a cauldron subsidence mechanism. Its complex magmatic history involved crystal fractionation, both insitu and at depth, coupled with episodic magma mixing in a deep magma chamber. Radioelement contents (means for the whole complex; 12.7 ppm Th, 2.9 ppm U, 4.1% K20) increase with magmatic differentiation and are concentrically zoned in the N Cruachan and Starav units. Mass balance calcUlations, incorporating radiometric, whole rock trace element, fission track and accessory phase microprobe data, show that uranium and thorium contents were, initially, controlled by the crystallisation of apatite + zircon + sphene ± allanite and chevkinite. Later, thorite and monazite became important thorium-hosts. Locally, enhanced uranium levels in the Starav Granites followed expulsion and limited outward migration of uranium-rich residual fluids. The distribution of rad10elements in surface samples suggests that heat production decreases with depth in some units. Similar studies have identified four units in the Cairngorm Granite; NE Granite - Porphyritic Granite - Microgranite - Main Granite. Radioelement contents increase with magmatic evolution from the N Granite to the Main Granite; 26.5 > 32.3 ppm Th, 4.3 > 10.1 ppm U, 4.6 > 4.7% K2n (mean values). Uranium and thorium contents were controlled,predominantly, by the crystallisation of apatite + zircon + sphene ± allanite in the NE Granite and of apatite + zircon + monazite + xenotime + Nb-Ta-oxides ± thorite ± uraninite in the Main Granite. Minor amounts of uranium reside in secondary sites in hydrothermally altered samples. Modelled surface heat flow anomalies are 5.8 mW m-2 and 23.0 mW m-2 for the Etive Complex and Cairngorm Granite respectively. Comparison of calculated and preliminary heat flow measurements in the Cairngorm granite indicates that at least 35% of the observed heat flow arises from radioactive sources in the granite and that background heat flow is low.

Accessory minerals in granitoids are major repositories of several geochemically-important trace elements and isotopes and in order to quantify the influence that they have over granitoid petrogenesis it is necessary to characterize fully their behaviour. In particular it is necessary to understand accessory mineral/melt partitioning of trace elements and within grain elemental diffusivities, the latter is of relevance when assessing the state of isotopic equilibration between a refractory accessory phase and a contacting melt. In this study the backscattered electron (BSE) imaging technique, coupled with quantitative electron microprobe analysis indicate that granitoid zircons and titanites (mainly taken from Caledonian intrusive complexes) are commonly compositionally zoned. The zoning textures observed in these minerals, namely crystal face-parallel zoning, non-planar compositional zoning (included here are subhedral and anhedral core structures) and compositional sector zoning, indicate that the kinetic factors of crystal growth, i.e. within magma elemental diffusion rates, crystal growth rates, interface kinetics and dissolution kinetics, are largely responsible for the patterns of compositional zoning that have been observed. This fording is in marked contrast to other studies which have assumed that kinetics are not important in crystallizing plutonic granitoid magmas. Accessory mineral growth histories have been studied in a few well constrained samples from the Caledonian-age Strontian Complex of NW Scotland. The zircons from the central intrusion of this composite pluton have abundant inherited cores. The cores contain a variety of zoning structures and have a wide range of composition, which are taken to indicate that the cores had a wide variety of ultimate sources. Titanites from both the outer and inner intrusions have compositional sector zoning and the range of composition shown by the titanites is largely due to this fact. In this pluton magma composition appears to have little influence on titanite chemistry. The REE abundances in both parts to the intrusion are largely controlled by the accessory phases and each of these phases have very different rock-normalised REE distribution patterns. These abundance patterns are dependent on the relative partition coefficients that each phase has for the REE, the accessory mineral assemblage present and the crystallization order of that assemblage. The zircons from the central acid member of the Strontian Complex, which are known to have substantial U-Pb inheritance were extracted and analysed for their Sm-Nd isotopic composition. The results apparently indicate that refractory zircons can also preserve their Sm-Nd isotopic composition, a phenomenon not previously reported. That is diffusion of Sm and Nd (and presumably the other REE) within refractory zircon at elevated temperatures appears to be sufficiently slow that complete isotopic equilibration between a zircon and a contacting melt may not always occur. Such disequilibrium potentially enables granitoid magma provenance to be studied with much greater resolution than hitherto possible.

This thesis is concerned with the mathematical aspects related to the optimal cutting of an object whose three-dimensional shape has been accurately and robustly reconstructed using appropriately developed computer-vision tools. First, a brief introduction to various one- and two-dimensional packing problems is presented. The Constrained Rectangle Packing problem which allows for defects to be modeled is then formulated and an efficient algorithm for solving it is presented. The two-stage stock-cutting problem according to which a set of rectangular pieces of prespecified dimensions are to be cut from a general shape object with general shape holes or defective regions is then investigated. It is shown how mathematical morphological operators can be vised in order to determine the optimal shifting for a given cutting pattern and proved that the problem of obtaining the optimal cutting pattern is NP-hard. However, the optimal solution to the unconstrained problem using mathematical programming is proposed. For the general problem good sub-optimal solutions are obtained using the technique of simulated annealing. Stereo-vision techniques are then employed for the accurate shape determination of the object to be cut. A three-dimensional reconstruction technique based on projective geometry is formally analysed and guidelines for its robust application are given. Finally, emphasis is placed on the correspondence problem, which becomes very difficult in the case of non-coplanar features and cameras set at 90 degrees from each other. It is shown how to cast the problem into an optimisation framework and a branch and bound algorithm is used in order to obtain the optimal solution. For increased robustness a Hough-Transform-like algorithm is also suggested. Both synthetic and real experimental results are presented throughout the thesis in order to illustrate the validity and usefulness of the proposed algorithms.

The Shap Granite outcrops in eastern Cumbria, N.W. England and is a post—orogenic granite intruded during the Lower Devonian (ie 394 Ma) into rocks of Ordovician to Siturian age. It is of adamellite composition and is notable in having megacrysts of orthoclase which crystallised late (relative to the matrix) by an essentially metasomatic process. Late in its cooling history, hydrothermal fluids resulted in alteration ano mineralisation in and about the joint structures. Comparison of whole — rock element and stable isotope data between the hydrothermally — altered and non —altered granites shows that this late — stage process- was isochemical and only involved localised redistribution of the available elements, the hydrothermal fluid being derived from the granite itself and acting in a closed system. The associated suite of granitic dykes extends the chemical range of Shap granitic rocks from the restricted compositions of the granite itsetf (around 68%)to 62 to 77% Si02. Mineralogical and chemical evidence suggests that the Shap magma compositions were controlled mainly by biotite and plagioclase fractionation over much of this silica range. The granite is intruded about much of its outcrop into rocks of the mid—Ordovician, calk—alkaline Borrowdatt Volcanic Group. The aureate is lkm wide and 'generally displays limited contact metamorphic reactions apart from in the Blue Quarry, where higher sub—surface heat flow during the granite's intrusion resulted in localised more extreme metamorphic and some metasomatic conditions resulting in the development of garnet veins. Analysis of 61 samples from the aureole region show only very limited modifications to their original calk—alkaline chemistry. Stable isotope and the whole rock geochemistry indicates that the contact metamorphism was essentialty, isochemical and that chemical interaction with the granite did not occur. Aureole metamorphic reactions took place at moderate temperatures (250 — 400°C) apart from in a narrow (<1000 zone about the granite contact where temperatures may have reached close to those of the granite-solidus (around 600°C). Xenoliths from the 'granite Pink quarries at Shap contain the same mineralogy as their host granite, including the megacryst orthoclase. The xenolith chemistry compares well with that of the more basic dykes, with the xenoliths - forming a coherent group over the compositional range 56 to 674 Sia. Comparison with the country—rock chemistry shows that the xenoliths were not externally derived but probably represent quenched, more basic, comaqmatic melts related to the generation of the main Shap Granite magma. Limited Sr and Nd isotope data for the xenoliths show that these isotopes were in equilibrium with the granite and lends strong support for the cogeneric origins and chemical relationships for the granites, aykes and xenoliths together. The narrow aureole width is typical of those formed by conductive ratner convective cooling with interaction with the adjacent granite limited to thermal effects and not involving the cycling of fluids through the granite or aureole as in convective pluton cooling.

The granitic rocks are subdivided into four series: tholeiitic, alkaline, calc-alkaline and mobilizates. These series can be formed from melting of mantle material (M-type granites) or from crustal rocks. There are granitic rocks formed from the mixing of these two magmas types. The rocks formed from crustal anatexis are subdivided into those formed from igneous rocks (I-type granites) and those formed from meta-sedimentary rocks (S-type granites). The former has similar characteristics to the mantle-derived granitoids. The mineral deposits related to igneous or mantle derived magma usually are Cu-Au, CUI Cu-Mo, Mo porphyries and have high oxygen fugacity and magnetic susceptibility (magnetite series). The Sn-W deposits usually are related to magma derived from meta-sedimentary or igneous rocks derived magma with low oxygen fugacity and magnetic susceptibility (ilmenite series). According to the tectonic setting, the granitoids rocks are classified as: Andino type, West Pacific type, Hercyno type, Caledonian type and Anorogenic (A-type granites).

Plutonium (Pu) is one of the key elements in high-level radioactive waste due to its long half-life. Understanding the sorption behavior of key radionuclides such as Pu and U is important to the safety assessment calculation for a deep geological repository for high-level radioactive waste. Europium (III) (Eu(III)), a chemical analogue of Pu, has shared similar sorption behaviors as Pu. The aim of this study is to investigate the sorption properties of europium onto MX-80 bentonite and crystalline rock (granite), a potential host rock for a deep geological repository for some countries, as a function of pH and ionic strength using batch experiment technique and surface complexation modeling. The experiments are conducted in Ca-Na-Cl solutions. For granite, the sorption coefficient Kd showed proportionate dependence on the pH. The sorption of Eu is dependent on ionic strength at near neutral to low pH region while not dependent on ionic strength at higher pH. For MX-80 bentonite, the sorption of Eu has little dependence on the ionic strength. A surface complexation modeling is also being carried out to examine the experimental results and identify the possible mechanism of the sorption. / Thesis / Master of Applied Science (MASc)