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No description available.

The aims of this work were to make a statistical study of variations in chemical composition within and between two major pelitic units in the Moine Series of Morar, western Inverness-shire, and to assess the metamorphic grade across the area by means of the calc-silicate bands found. Two of the major pelitic units, the Lochailort Pelitic Group and the Garnetiferous Pelite, were sampled to a rigid sampling plan which allowed analysis of variance techniques to be applied to the results, in a study of chemical variation within each of the units. Stepwise linear discriminant function analysis of the data was also undertaken, to provide functions which could be used to separate the two units on the basis of their chemical compositions. These derived functions could also be used to classify unknown samples and assign them to their correct stratigraphic position. Calc-silicate bands found as a minor rock type within the area may be used as precise indicators of metamorphic grade, since their chemistry determines their mineralogical response to metamorphism in a predictable fashion. Evidence from the less responsive pelites indicates that metamorphic grade rises generally eastwards across Morar, and a study of the calc-silicates, while confirming this, also provided evidence of a later, retrogressive event in the east of the area. In order to obtain large numbers of chemical analyses, rapid X-ray fluorescence analytical techniques were employed. For major element analysis a fusion method of sample preparation was adopted, and a new method of calibration was devised which allows a large range of rock compositions to be analysed using a single set of linear calibration regression equations.

Any industrial site producing contaminants (including chemical and radiological materials), will be constructed on or below the surface, whose associated properties determine how fluid and contaminants travel. The Dounreay Nuclear Power Establishment offers a unique opportunity to understand bedrock geology, superficial deposits, shallow fractures, and their controls on fluid and contaminant pathways. This is due to its complex history, possible contaminants and extensive prior site investigations. Three-dimensional geological modelling is becoming an integral part of site investigations as affordable technology becomes more powerful. Using previously collected, data and state-of-the-art modelling, a high-resolution geological model has been created based on understanding the cyclicity of the Devonian sedimentation of the Orcadian Basin. This underlies the site providing a framework for discrete fracture network and stochastic facies modelling. A discrete fracture network, for three fracture sets, has been created for the bedrock geology through statistical analysis of scanline and borehole data, and stochastic simulations of fracture intensity throughout the geological model. Due to the heterogeneity of the superficial deposits, a stochastic simulation was used to interpolate five distinct superficial facies, considered to influence contaminant pathways and identified from geotechnical logs; 1–Clay, 2–Sand, 3–Gravel, 4–Silt and 5–Peat. Fracture intensity of the hydraulically conductive bedding-parallel fracture set decreases logarithmically with increasing depth. The decreasing fracture intensity of the bedding-parallel fractures reflects a decreasing horizontal hydraulic conductivity, which at 100m levels off and becomes approximately equal to the vertical hydraulic conductivity. The superficial deposits are predominantly clay, with the maximum hydraulic conductivity associated with the gravel facies. The gravel facies provide connectivity from the land surface to the bedrock and associated fracture networks. Methodologies used here can be applied to any site investigation, providing adequate data is available, and by integration, analysis and three-dimensional modelling of the shallow subsurface, a better understanding of contaminant pathways and uncertainties can therefore be achieved.

The Ben Nevis volcanic-plutonic Complex was intruded into garnet grade Precambrian metasediments in the Southwest Highlands of Scotland towards the end of the Caledonian Orogeny. A variety of techniques have been applied to the Ben Nevis Complex in order to model its volcanic and plutonic evolution; these include: field mapping, petrography, mineral chemistry, whole rock major and trace element geochemistry and a combined study of the isotopes of neodymium and strontium. Rocks of the volcanic pile are subdivided into the following formations; the Allt a' Mhuillin formation, the Coire na Ciste formation, the Ledge Route formation and the Summit formation, and these overlie a basement of Dalradian schist. Fine grained metasediments of the Allt a' Mhuillin formation were deposited in a lacustrine basin into which entered a series of non-volcanic mass flow units. Non-volcanic deposition was terminated with the entry of the first volcaniclastic lahars of the Coire na Ciste formation into the Ben Nevis basin. Block and ash flows, lava flows and sills are also found in this formation. The Ledge Route formation testifies to a complex period of quiescence, airfall deposition and mass flow movement after which localised flows of lava dominate the overlying Summit formation. A single felsite dyke is found intruding the volcanic pile and is correlated with early members of the Ben Nevis dyke swarm in the northern area of the Ben Nevis Complex. Plutonic rocks of the Ben Nevis Complex are subdivided into the Fine Quartz Diorite, Sgurr Finnisg-aig Quartz Diorite, Coarse Quartz Diorite, Porphyritic Outer Granite and Inner Granite; these were intruded to a high level in the crust. A dextral stress regime operated during the intrusion of the plutonic rocks. Each of the above units was intruded as a series of pulses. Mass balance and qualitative trace element vector modelling (Rayleigh crystallisation) is able to model the geochemical evolution of the Porphyritic Outer Granite using plagioclase, amphibole, biotite and magnetite as the fractionating assemblage. Pyroxene is found as a phenocryst and as a groundmass phase in the quartz diorites with calcic amphibole found mainly as a replacement mineral after pyroxene; however, trace element modelling identifies amphibole as a fractionating phase. Isotopic modelling of the Ben Nevis Complex indicates the involvement of at least three components; these being a mantle source, a lower crustal source with similar isotopic characteristics to the Islay-Colonsay-Basement and, of lesser importance, Dalradian metasediments. No single parental magma can explain the geochemical and isotopic variation of the Ben Nevis Complex.