4 resultados para British Isles

em Aston University Research Archive


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Two aspects of gold mineralisation in the Caledonides of the British Isles have been investigated: gold-telluride mineralisation at Clogau Mine, North Wales; and placer gold mineralisation in the Southern Uplands, Scotland. The primary ore assemblage at Clogau Mine is pyrite, arsenopyrite, cobaltite, pyrrhotine, chalcopyrite, galena, tellurbismuth, tetradymite, altaite, hessite, native gold, wehrlite, hedleyite, native bismuth, bismuthunite and various sulphosalts. The generalised paragenesis is early Fe, Co, Cu, As and S species, and later minerals of Pb, Bi, Ag, Au, Te, Sb. Electron probe micro-analysis (EPMA) of complex telluride-sulphide intergrowths suggests that these intergrowths formed by co-crystallisation/replacement processes and not exsolution. Minor element chemical variation, in the sulphides and tellurides, indicates that antimony and cadmium are preferentially partitioned into telluride minerals. Mineral stability diagrams suggest that during gold deposition log bf aTe2 was between -7.9 and -9.7 and log bf aS2 between -12.4 and -13.8. Co-existing mineral assemblages indicate that the final stages of telluride mineralisation were between c. 250 - 275oC. It is suggested that the high-grade telluride ore shoot was the result of remobilisation of Au, Bi, Ag and Te from low grade mineralisation elsewhere within the vein system, and that gold deposition was brought about by destabilisation of gold chloride complexes by interaction with graphite, sulphides and tellurbismuth. Scanning electron microscopy of planer gold grains from the Southern Uplands, Scotland, indicates that detailed studies on the morphology of placer gold can be used to elucidate the history of gold in the placer environment. In total 18 different morphological characteristics were identified. These were divided on an empirical basis, using the relative degree of mechanical attrition, into proximal and distal characteristics. One morphological characteristic (a porous/spongy surface at high magnification) is considered to be chemical in origin and represent the growth of `new' gold in the placer environment. The geographical distribution of morphological characteristics has been examined and suggests that proximal placer gold is spatially associated with the Loch Doon, Cairsphairn and Fleet granitoids. Quantitative EPMA of the placer gold reveals two compositional populations of placer gold. Examination of the geographical distribution of fineness suggests a loose spatial association between granitoids and low fineness placer gold. Also identified was chemically heterogeneous placer gold. EPMA studies of these heterogeneities allowed estimation of annealing history limits, which suggest that the heterogeneities formed between 150 and 235oC. It is concluded, on the basis of relationships between morphology and composition, that there are two types of placer gold in the Southern Uplands: (i) placer gold which is directly inherited from a hypogene source probably spatially associated with granitoids; and (ii) placer gold that has formed during supergene processes.

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The sulphide mineralisation at Avoca and Parys Mountain is intimately related to volcanism and is of volcanogenic sedimentary type. The associated volcanics are predominantly pyroclastics of rhyodacitic composition and of Upper Ordovician age. They were erupted from discrete small volcanic centres, products of single local volcanic events, whose spatial distribution was related to fractures in the sialic basement of the paratectonic Caledonides of the British Isles. These fractures resulted in linear controls on volcanic, plutonic and tectonic features; they are the result of predominantly strikeslip stresses generated in this part of the European plate during closure of the Iapetus ocean. The mineralisation, predominantly pyritic, consists of a siliceous footwall zone containing bedded and cross-cutting sulphides and an overlying non-siliceous zone of bedded sulphides which may show vertical zoning of metal ratios. The sulphides are associated with chert and iron formation and have been affected by slumping. Mineralisation developed near the vents during intense fumarolic activity accompanying strong volcanism; at Parys Mountain, fumarolic activity commenced prior to, and continued after, the rnain volcanic event. Comparison with similar deposits in Newfoundland and at Bathurst, in the Canadian Appalachians, shows that mineralisation can be associated with any discrete pulse of acid magmatism in shallow subaqueous conditions. Local features of the sulphides and associated sediments are similar, although in more distal deposits (with respect to a volcanic centre) footwall alteration and mineralisation are less well developed. The nature of the basement and the presence or absence of earlier volcanics are not critical, although establishment of a local tensional regime at the time of ore formation may be important. The volcanics hosting mineralisation are rhyodacitic pyroclastics, generally related to a small centre and representing a single episode of volcanism.

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This study is toe first documented account in the British Isles of an evaluation of the effectiveness of client-centred counselling with young offenders in secure residential care. It is a test of Rogers' (1957) position on the 'necessary and sufficient' conditions of therapeutic personality change within a counselling relationship. Forty teenage male offenders, the subjects of Training School Orders, were randomly allocated in equal numbers to either an experimental or control group. Boys in the experimental group received weekly individual sessions of client-centred counselling over a seven month period. Boys in the control group received no formal counselling but were shown to have similar intellectual, personality, socio-economic and criminal backgrounds to those in the experimental group. It was hypothesised that counselled subjects would show more positive outcomes than control subjects over a range of measures relating to criminal behaviour and self-conception. The results indicated that the counselled subjects had a significantly lower rate of offending and a srnaller range of offences over a mean follow-up period of 2.5 years. They were also licensed from the institution significantly earlier and spent less time in custody during a one year follow-up after counselling was completed. Self-conception measures gave less clear-cut results. The direction of change towards better adjustment favoured the counselled subjects but the magnitude was often small. Those counselled subjects with most positive behaviour change tended to have significantly improved self-evaluation, less self/ideal self discrepancy and more variation on 'actual' self concept compared to pre-counselling. The results are discussed in the context of client-centred theory, methodological adequacy of the experimental design, and their application to the future treatment of young offenders in secure residential care.

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This volume focuses on the closely allied yet differing linguistic varieties of Birmingham and its immediate neighbour to the west, the industrial heartland of the Black Country. Both of these areas rose to economic prominence and success during the Industrial Revolution, and both have suffered economically and socially as a result of post-war industrial decline. The industrial heritage of both areas has meant that tight knit and socially homogeneous individual areas in each region have demonstrated in many respects little linguistic change over time, and have continued to exhibit linguistic features, especially morphological constructions, peculiar to these areas or now restricted to these areas. At the same time, immigration from other areas of the British Isles over time, from Commonwealth countries and later from EU member states, together with increased social mobility, have meant that newly developing structures and more widespread UK linguistic phenomena have spread into these varieties. This volume provides a clear description of the structure of the linguistic varieties spoken in the two areas. Following the structure of the Dialects of English volumes, it provides: •A comprehensive overview of the phonological, grammatical and lexical structure of both varieties, as well as similarities between the two varieties and distinguishing features •Thorough discussion of the historical and social factors behind the development of the varieties and the stigma attached to these varieties •Discussion of the unusual situation of the Black Country as an area undefined in geographical and administrative terms, existing only in the imagination •Examples of the variety from native speakers of differing ethnicities, ages and genders •An annotated bibliography for further consultation