This research aims to better understand drainage systems during mid to late Large Igneous Province (LIP) formation. A multidisciplinary study was conducted on the Lewiston Basin in the Columbia River Flood Basalt Province and the Skye Lava Field in the North Atlantic Igneous Province. A general model for drainage systems in LIPs was developed with three stages. In the early-LIP stage, the volcanic and drainage systems are confined to small basins, but as the volumetric eruption rate increases the regional drainage system is forced to the edge of the lava field. During the mid-LIP stage, the eruption rate decreases and the drainage system moves into the lava field, depositing channel sediments in the lowest parts of province while finer sediments or palaeosols develop in topographically higher areas. In the Skye Lava Field the drainage system was dominated by the uplift of the Rum Central Igneous Complex and included the incision of shallow valleys, whereas in the Lewiston Basin the most important effect was the structural control on basin topography. During the lateLIP stage, topographically high areas experience significant incision into the lava field which are filled by intracanyon flows (thick canyon-filling lava flows). These intracanyon flows may compartmentalise potential reservoirs deposited between earlier lava flows. Siliciclastic sand bodies were observed up to 12 m thick and 850 m across with minor exposure gaps, and were correlated across up to 15 km. The palynofloras associated with a number of palaeoenvironments in each province were identified the effects of other controls on the palaeoecology such as moisture availability, ashfall and substrate were established. The changes in the paJaeoclimate of the Lewiston Basin were studied using palaeosol geochemistry and palynology.

The petrogenetic processes through which peralkaline silicic magmas are generated in oceanic island environments, as well as the controls on their eruptive behaviour, are not well understood. This study utilises two such systems, Pico Alto and Furnas, Azores, to elucidate the petrogenesis, storage conditions, and eruption of peralkaline silicic magmas, and employs a variety of complementary approaches, including petrographic analysis, whole rock and mineral chemistry, thermobarometry, and petrogenetic modelling. For both of the investigated systems, shallow-crustal, volatile-undersaturated fractional crystallisation of mantle-derived parental melts is the dominant mechanism of magmatic differentiation. Magma mixing and mingling processes are also shown to play a key role, with abundant evidence for mixing of trachytic magmas with either trachytic or mafic magmas. Furthermore, mingling between trachytic magmas and syenitic crystal mushes is recorded as enclaves in syenitic ejecta which represent the near-complete, in-situ crystallisation of trachytic magmas in a thermal boundary layer at the margins of a magma reservoir. Phase assemblages of the syenitic ejecta range from miaskitic to agpaitic, and include rare zirconosilicates such as eudialyite and dalyite. The observed compositional variability of dalyite is demonstrably linked to the compositional evolution of residual melt, coupled with a nucleation delay introduced by variable pore sizes. At both volcanic centres, peralkaline silicic magmas accumulate in shallow crustal reservoirs and develop vertical compositional zonation. These reservoirs inhibit the ascent and eruption of less evolved compositions, and generate a compositional Daly gap. Contrasting eruptive behaviour observed both within and between the volcanic centres of this study is shown to be linked primarily to the degree of pre-eruptive magma volatile undersaturation and, at Furnas, interaction with external water. The presented models provide new insights into peralkaline magmatic systems, and may be applicable to similar peralkaline silicic systems, both within the Azores archipelago, and at similar oceanic island settings worldwide.

This thesis focuses on the development of the black shales belonging to the lower Silurian Formigoso Formation (Fm.) situated within the Cantabrian Fold Belt, Northern Spain. The geochemical data obtained by the use of an energy-dispersive Niton XL3t XRF analyser under controlled laboratory conditions is comparable to that of conventional wavelength dispersive XRF analysers. The in-situ field analysis resulted in similar geochemical signals and elemental concentrations to that of the laboratory analysed samples. The high-resolution geochemical database, consisting of 4148 readings of the Formigoso Fm. was used to characterise the shales of the Formigoso Fm. relative to a number of international shale standards. Following this geochemical characterisation, a number of palaeoenvironmental proxies for [1] anoxia reconstructions, [2] palaeosalinity, [3] palaeohumidity, [4] weathering indices, and finally [5] bioproductivity were utilised. The combined outcome of these proxies together with field-based sedimentological observations led to a detailed reconstruction of the environment that prevailed during the deposition of the Bernesga Mb. black shales. A generic model is developed for the formation of these organically enriched sediments. This model is subsequently compared to previously published Silurian, black ‘hot’ shale models. The major parameters controlling the development of the Cantabrian black shale deposits were mainly the presence of a pronounced palaeorelief, which was generated by a combination of tectonic pulses related to the widening of the Rheic Ocean to the north and glaciogenic processes of the Hirnantian ice masses to the south. Orbital parameters or ‘deep time cycles’, mainly Obliquity and Eccentricity in combination with tectonic pulses led to high resolution sea-level oscillations and consequent cyclic behaviour of the redox elements recorded within the ‘hot’ shale deposits of the southern Cantabrian Basin. Additionally, 209 measurements of 76 international and inter-laboratory standards were performed to formulate new equations for the precise calibration of major and trace elements.

This study examines the tectonic evolution of the Mersin ophiolite of the central Tauride of Turkey, using palaeomagnetic, structural and geochemical analyses. This ophiolite represents one of the best examples of Tethyan-type ophiolites formed by supra-subduction zone spreading within the northern Neotethyan Ocean basin during the Late Cretaceous. It exposes a 3.0 km section of lower crustal, cumulate rocks, and tectonically separated exposures of the underlying mantle sequence and metamorphic sole, both of which are cut by basaltic dykes. Stepwise thermal and alternating field demagnetization of ultramafic and gabbroic cumulates from 18 sites mostly identified single components of remanent magnetization characterized by ENE-directed, moderately upwards inclined directions in geographic coordinates with high coercivities/high unblocking temperatures. The slight increase in scattering in remanence directions after tilt correction has been interpreted to be related to local variations in orientation of cumulates layering within the magma chamber. Rock magnetic investigations showed that magnetite is the main magnetic mineral in the majority of ultramafic, gabbro and dyke rock samples, and rock magnetic and demagnetization characteristics suggest that the samples carry thermoremanent magnetizations acquired during crustal accretion. Net tectonic rotation analyses show that all the units of the Mersin ophiolite, including lower crustal cumulates, dykes in the mantle sequence and dykes in the metamorphic sole have experienced large clockwise rotations around NE- trending, moderately plunging to sub-horizontal axes. Correcting anisotropy of magnetic susceptibility data for the effects of these rotations suggests that magmatic flow in the cumulates had an initial NNE-SSW orientation, which if assumed to relate to seafloor spreading suggests that the Mersin spreading axis was oriented WNW-ESE. This is consistent with regional palaeogeographic reconstructions. The net tectonic rotation data show that dykes in the metamorphic sole are rotated by c. 45°, significantly less than the c. 115° rotations seen in the mantle sequence and in the cumulate sequences of the overlying thrust sheets. These results therefore document an initial stage of intra-oceanic clockwise rotation of the ophiolite that occurred after initial detachment but prior to emplacement of dykes cutting the metamorphic sole. Subsequent additional clockwise rotation (of all units) may be attributed to further intra-oceanic rotation (preferred interpretation) or to later emplacement of the ophiolite onto the Tauride continental margin. Finally, some new, preliminary data are presented from the Lizard ophiolite of Cornwall in Appendix A, forming the results of a training project undertaken while awaiting permission for fieldwork in Turkey.

No description available.

This thesis investigates the origin of large-scale sandstone intrusions.  A new approach combining seismic, well data, core and outcrop observations with numerical modelling has been undertaken. Two possible end members of saucer-shaped, seismic-scale sandstone intrusions from the North Sea were identified on the basis of seismic data and core observation.  Diagnostic criteria were proposed to differentiate between fully and only partially injected sand bodies.  Outcrop and core data presented in this thesis provide a direct example and analogue for seismic and sub-seismic scale sandstone intrusions, highlighting the brittle nature of the host rock deformation at all levels within the examined intrusion complexes.  On this basis, the rheological behaviour of the host strata at the time of sand injection is inferred to be elastic with brittle fracturing.  This outcome is used as an input condition for Finite Difference and Finite Element modelling that aim to test hypotheses describing triggering mechanisms and estimate their regional extent, depth and overpressures present during sand injection.  The results of numerical modelling indicate that formation of the North Sea sandstone intrusions could potentially be triggered by catastrophic event(s) such as a meteorite impact or earthquakes, leading to sand liquefaction and remobilization.  It has also been shown that depths at which sand injection can take place reach 1 km.  Only supra-lithostatic pressures generate bodies composed of lower, bedding concordant part of intruded or depositional origin feeding inclined dykes at its marginal parts resembling those observed today on seismic data from the North Sea and in outcrops.

This study used Raman spectral analysis to characterise the structural order of carbon in three carbonaceous chondrites and twelve achondrites. The achondrites analysed were a group of carbon-rich meteorites, known as ureilites. These meteorites are composed primarily of olivine and pyroxene and have igneous textures but contain noble gases and primitive oxygen isotopes which appear to contradict their high temperature origin, which has led to the group being described as “enigmatic” by some authors. This study used Raman spectral analysis to show that ureilite carbon is heterogeneous, even at the micrometer scale, and is derived from more than one source. In order to better understand the processes involved in ureilite formation, terrestrial analogues containing carbonaceous material with similar spectral characteristics to the meteorites were identified. Analysis of terrestrial samples showed that the sedimentary carbon can be incorporated into igneous rocks with little structural change, suggesting that the same may be true for carbonaceous material in ureilites. Although the terrestrial carbon is biogenic in origin, it is structurally similar to pre-biotic organic matter found in meteorites. Carbon can be used as an effective tracer for geological events, such as melting and heating, which appear to be ubiquitous in planetary evolution. This study concluded that carbon is a primary component of melts on the ureilite parent body (UPB) and that impact processes have increased the heterogeneity of ureilite carbonaceous material. Carbon is likely to have been remobilised by later impact events, explaining the lack of correlation between carbon content and isotopic values with other geochemical parameters. Spectral analysis suggested that most of the carbon in ureilites is derived from primitive material.

This thesis is an account of an investigation into the structure, petrology and mineralogy of a small Tertiary intrusive centre in the Vididalur-Vatnsdalur area near the north coast of Iceland. The area concerned lies in the Tertiary area west of the neovolcanic zone. In upper Tertiary times the extrusion of flood basalts in the area studied was locally interrupted by the building of a central volcano characterized by distinctive basalts, andesites and pyroclastics, some of which interfingered with contemporaneously extruded flood basalts. The first episode of this central volcanic activity, of which only the top is seen in the area studied, was subsequently buried by the transgressing flood basalts, and slow downsagging occurred in parts of the area along the prevailing north to north-northeast fracture system. A second central volcanic episode produced basalt, andesite and rhyolite extrusions and some pyroclastics in the northeastern part of the area following the flood transgression. Injection of thin basic dykes proceeded parallel to the two phases of central activity and continued during a final episode in which thin pale grey basalts similar to the Lower Pleistocene to Recent flows elsewhere in Iceland were extruded on to the irregular central volcano land surface. Two phases of intrusive activity proceeded parallel to the extrusive activity, the older More deeply eroded First Phase products being emplaced in the time interval during which the older flood basalts buried the newly extruded earlier central volcano lavas. A consecutive Second Phase of intrusive activity proceeded simultaneously with the second central volcanic episode and its less deeply eroded products show many similarities to the contemporaneous extrusions. These First and Second Phase intrusions are probably the upper apophyses of larger bodies concealed at depth. The intrusions which form the main part of the study are concentrated about an intrusive/extrusive centre in northern Vididalsfjall, and consist of coarse- and fine-grained basic to acid series, ranging in the First Phase from olivineeucrites (bytownite cumulates) through gabbros (labradorite cumulates), hybrid diorite and intermediate-acid hybrid types to acid granophyres. The First Phase was initiated by the intrusion of the eucrites and a dense swarm of tholeiitic cone-sheets centred on a focus about 5 km below northern Vididalsfjall. Commingling of the simultaneously available diorite and granophyre magma later in the First Phase resulted in the formation of small volumes of acid-intermediate hybrid rocks. The Second Phase intrusive activity is expressed as small high-level intrusions and began with a new supply of olivinetholeiite magmas which was injected along cone-fractures to form a late set of high-level cone-sheets centred on a focus about 2 km below northern Vididalsfjall. Cogenetic bytownite cumulates were emplaced as small high-level intrusions, but coarse-grained rocks and acid rocks of Second Phase age are rare in the area studied. iii. A broad aureole of hydrothermally altered rocks surrounds northern Vididalsfjall and smaller alteration zones surround other smaller regions cut by vents and intrusions; these altered and injected zones are taken to represent the eruptive channels at the core of the Vididalur-Vatnsdalur volcano. The intrusive rocks are all plagioclase-pyroxene-ore assemblages with or without olivine, alkali feldspar and quartz, and the First Phase types show a gradation from basic rocks bearing calcic plagioclase and magnesian augite to acid rocks containing sodic plagioclase anorthoclase and ferrian augite. The Second Phase rocks show broad petrographic similarity to those of the First Phase but coarse-grained intermediate and acid types are not found, and the basic rocks are richer in olivine than corresponding First Phase types. All the rocks examined show textural and mineralogical evidence of a high degree of fractionation and rapid final cooling at high crustal levels; the plagioclase of phenocryst rims and groundmasses is in a high-temperature structural state, the calcium-rich pyroxenes have immature exsolution textures, the olivines are strongly zoned and interstitial glassy or salic material is abundant. Many of the acid minor intrusions contain tridynlite paramorphed by quartz. Chemical analyses of 14 Vididalur-Vatnsdalur rocks show that they are low in alumina, combined alkalis and magnesia, and are relatively rich in iron, and titania, as are other Tertiary Icelandic tholeiites, with soda present in greater quantity than potash. The analyses of these basic intermediate and acid rocks fit on the iron-enriched trend for tholeiites (Nockolds a.nd AlIen, 1956) which suggests that the First and Second Phase sequences may have originated by -contiriuous fractionation of basic tholeiitic uuterinl. However there is little direct evidence of a tholeiite fractionation origin for the First Phase granitic acid rocks, and the presence of a few small veins of remelted acid material at some localities casts doubt on a fractionation origin for these granophyres and granites of the Vididalur-Vatnsdalur area.

William S. Song and Bruce R. Musicus. / Also issued as Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1989. / Includes bibliographical references (p. 141-143). / Supported in part by U.S. Air Force Office of Scientific Research. AFOSR 86-0164 Supported in part by Charles S. Draper Laborarory. DL-H-404158

Η παρούσα διπλωματική εργασία έχει σαν αντικείμενο μελέτης την αποτίμηση των φυσικών παραμέτρων των μαλακών βράχων.Η περιοχή μελέτης τοποθετείται στο βορειοδυτικό τμήμα της Πελοποννήσου και συγκεκριμένα στο Νομό Αχαΐας. Οι ιδιαιτερότητες των φυσικών χαρακτηριστικών των σχηματισμών αυτών απαιτούν τη συστηματική τους διερεύνηση. Για το λόγο αυτό η μελέτη τους αποκτά μεγάλο ενδιαφέρον. Η εργασία περιλαμβάνει τα παρακάτω στάδια: -Περιγραφή των γεωλογικών συνθηκών σε ευρεία κλίμακα και συγκέντρωση τεκτονικών και σεισμικών στοιχείων της ευρύτερης περιοχής μελέτης. -Λεπτομερής εξέταση, διαχωρισμός και ακριβής προσδιορισμός των θέσεων δειγματοληψίας της περιοχής μελέτης. -Δειγματοληψία από τους σχηματισμούς που απαντώνται στην περιοχή και εκτέλεση εργαστηριακών δοκιμών -Προσδιορισμός των φυσικών παραμέτρων των υπό εξέταση υλικών -Στατιστική επεξεργασία των τιμών των εργαστηριακών δοκιμών με σκοπό την εξαγωγή διαφόρων συμπερασμάτων για τη μηχανική συμπεριφορά των μαλακών βράχων. Η εργασία αυτή εστιάστηκε στη διερεύνηση της αποσαθρωσιμότητας των μαλακών βράχων με εκτέλεση δοκιμών χαλάρωσης (slake durability test). Προς την κατεύθυνση αυτή έγιναν διαδοχικοί κύκλοι της δοκιμής χαλάρωσης (μέχρι 5 κύκλοι) για τη καλύτερη διερεύνηση του φαινομένου. / The aim of this thesis is the study of natural parameters of soft rocks. The region of study is placed in the north-western department of Peloponnese and concretely in the Prefecture Achaia. The particularities of natural characteristics of this shapings require their systematic investigation. For this reason their study acquires big interest. The work includes the following stages: - Description of geological conditions in wide scale and concentration of tectonic and seismic elements of the wider region of study. - Examination and precise determination of places of sampling of region of study. - Sampling from the shapings in the region and implementation of laboratorial trials - Determination of natural parameters of materials under review. - Statistical analysis of prices of laboratorial trials in order to export various conclusions on the mechanic behavior of soft rocks. This work was focused in the investigation of durability of soft rocks with implementation of trials of slake durability test. To this direction they became successive circles of trial of slake durability test (up to 5 circles) for the better investigation of the phenomenon.