Gold in the Dalradian terrane : a review of previous work

The Dalradian Supergroup comprises a Late Precambrian sequence of marine clastic sedimentary rocks and minor basic volcanic rocks which was folded and metamorphosed during the early Palaeozoic Caledonian Orogeny. Intrusive igneous rocks are widespread throughout the Dalradian terrane. The most important in terms of gold metallogenesis are the post-tectonic granites which comprise a diverse suite of calc-alkaline intrusions emplaced between 420 and 395 Ma. Numerous occurrences of gold in bedrock and alluvium are documented in the Dalradian terrane of Scotland. Mesothermal vein occurrences are the most important and include the Cononish deposit, near Tyndrum in Perthshire, where planning permission for mining has been granted. Gold mineralisation of several other styles, including intrusion-related, epithermal, stratiform and occurrences associated with mafic-ultramafic intrusions, is also present. This report has been compiled for the BGS Core Programme project ‘Sedimentary Basin Resources: Gold in orogenic extensional basins – the Dalradian’. This project, carried out between 1997–2000, was designed to investigate the factors controlling the distribution of gold in the Dalradian and to develop a predictive metallogenic model for gold mineralisation in this terrane. This report provides a` review of known gold occurrences and the results of past mineral exploration activity in the Dalradian terrane. The latter has been compiled from records held in BGS archives and the available data are summarised in a series of appendices. Exploration for metalliferous mineralisation has been carried out widely in the Dalradian terrane by commercial mining companies and by BGS. In the 1970s most work focused on Cu, Pb, Zn, Ni and Mo, while more recently, from 1981 onwards, precious metals (Au and PGE) were the prime target. Between 1972 and 1984 the DTI sought to encourage private-sector mineral exploration by the provision of grants under the Mineral Exploration and Investment Grants Act (MEIGA). About 150 reports derived from these projects are available on open-file at BGS. Exploration by BGS was carried out mainly through the DTI-funded Mineral Reconnaissance Programme (MRP), which ran between 1972 and 1997. Nearly 150 reports and associated data releases were produced by the MRP. Together the MEIGA and MRP reports have been the major sources of information used in this report. The combination of improved genetic models for gold deposits, the increased availability of multidisciplinary digital geoscience data and the information on previous exploration summarised in this report provides a sound basis for research on gold mineralisation in the Dalradian terrane. Potential exists in a range of settings that may host economic gold deposits

Understanding Galaxy Formation and Evolution

The old dream of integrating into one the study of micro and macrocosmos is now a reality. Cosmology, astrophysics, and particle physics intersect in a scenario (but still not a theory) of cosmic structure formation and evolution called Lambda Cold Dark Matter (LCDM) model. This scenario emerged mainly to explain the origin of galaxies. In these lecture notes, I first present a review of the main galaxy properties, highlighting the questions that any theory of galaxy formation should explain. Then, the cosmological framework and the main aspects of primordial perturbation generation and evolution are pedagogically detached. Next, I focus on the ``dark side'' of galaxy formation, presenting a review on LCDM halo assembling and properties, and on the main candidates for non-baryonic dark matter. It is shown how the nature of elemental particles can influence on the features of galaxies and their systems. Finally, the complex processes of baryon dissipation inside the non-linearly evolving CDM halos, formation of disks and spheroids, and transformation of gas into stars are briefly described, remarking on the possibility of a few driving factors and parameters able to explain the main body of galaxy properties. A summary and a discussion of some of the issues and open problems of the LCDM paradigm are given in the final part of these notes.Comment: 50 pages, 10 low-resolution figures (for normal-resolution, DOWNLOAD THE PAPER (PDF, 1.9 Mb) FROM http://www.astroscu.unam.mx/~avila/avila.pdf). Lectures given at the IV Mexican School of Astrophysics, July 18-25, 2005 (submitted to the Editors on March 15, 2006

Velocity-space sensitivity of the time-of-flight neutron spectrometer at JET

The velocity-space sensitivities of fast-ion diagnostics are often described by so-called weight functions. Recently, we formulated weight functions showing the velocity-space sensitivity of the often dominant beam-target part of neutron energy spectra. These weight functions for neutron emission spectrometry (NES) are independent of the particular NES diagnostic. Here we apply these NES weight functions to the time-of-flight spectrometer TOFOR at JET. By taking the instrumental response function of TOFOR into account, we calculate time-of-flight NES weight functions that enable us to directly determine the velocity-space sensitivity of a given part of a measured time-of-flight spectrum from TOFOR

Relationship of edge localized mode burst times with divertor flux loop signal phase in JET

A phase relationship is identified between sequential edge localized modes (ELMs) occurrence times in a set of H-mode tokamak plasmas to the voltage measured in full flux azimuthal loops in the divertor region. We focus on plasmas in the Joint European Torus where a steady H-mode is sustained over several seconds, during which ELMs are observed in the Be II emission at the divertor. The ELMs analysed arise from intrinsic ELMing, in that there is no deliberate intent to control the ELMing process by external means. We use ELM timings derived from the Be II signal to perform direct time domain analysis of the full flux loop VLD2 and VLD3 signals, which provide a high cadence global measurement proportional to the voltage induced by changes in poloidal magnetic flux. Specifically, we examine how the time interval between pairs of successive ELMs is linked to the time-evolving phase of the full flux loop signals. Each ELM produces a clear early pulse in the full flux loop signals, whose peak time is used to condition our analysis. The arrival time of the following ELM, relative to this pulse, is found to fall into one of two categories: (i) prompt ELMs, which are directly paced by the initial response seen in the flux loop signals; and (ii) all other ELMs, which occur after the initial response of the full flux loop signals has decayed in amplitude. The times at which ELMs in category (ii) occur, relative to the first ELM of the pair, are clustered at times when the instantaneous phase of the full flux loop signal is close to its value at the time of the first ELM

Hyperglycaemic preterm babies have sex differences in insulin secretion

Background: Hyperglycaemia is a common complication of prematurity and is associated with neonatal mortality and morbidity, yet the aetiology is incompletely understood. C-peptide has been used in adults to estimate endogenous insulin secretion due to its simple clearance kinetics. Objective: To determine insulin secretion calculated from plasma C-peptide concentrations in hyperglycaemic preterm babies. Methods: A retrospective analysis of a cohort of 41 very preterm babies (median gestational age, weeks: 27.2 (26.2-28.7)) enrolled in a randomised controlled trial of tight glycaemic control when they developed hyperglycaemia (2 consecutive blood glucose concentrations (BGC) > 8.5 mmol.L-1). Insulin secretion was determined using a steady state analysis of a 2 compartment C-peptide kinetic model. Results: BGC, plasma insulin concentration, plasma C-peptide concentrations and insulin secretion were higher at randomisation than 1-2 weeks following randomisation (p≤0.02). Insulin secretion was higher in girls (11.7 (5.3-18.7) vs. 4.7 (2.1-8.3) mU.L-1.kg-1.min-1, p0.25). Insulin secretion was lower in samples taken during exogenous insulin delivery (3.7 (1.8 - 6.9) vs. 9.8 (4.7 - 17.8) mU.L-1.kg-1.min-1, p=0.02). Conclusions: Insulin secretion was higher when babies had higher BGC, indicating endogenous insulin secretion is sensitive to BGC. Girls had higher insulin secretion, at similar blood glucose and plasma insulin concentrations, than boys

A C-Peptide-Based Model of Pancreatic Insulin Secretion in Extremely Preterm Neonates in Intensive Care

Background: Model-based glycaemic control relies on sufficiency of underlying models to describe underlying patient physiology. In particular, very preterm infant glucose-insulin metabolism can differ significantly from adults, and is relatively unstudied. In this study, C-peptide concentrations are used to develop insulin-secretion models for the purposes of glycaemic control in neonatal intensive care. Methods: Plasma C-peptide, Insulin, and blood glucose concentrations (BGC) were retrospectively analyzed from a cohort of 41 hyperglycemic very preterm (median age 27.2 [26.2 - 28.7] weeks) and very low birth-weight infants (median birth weight 839 [735 – 1000] g). A 2-compartment model of C-peptide kinetics was used to estimate insulin secretion. Insulin secretion was examined with respect to nutritional intake, exogenous and plasma insulin concentration, and BGC. Results: Insulin secretion was found to be highly variable between patients and over time, and could not be modeled with respect to age, weight, or protein or dextrose intake. In 13 of 54 samples exogenous insulin was being administered, and insulin secretion was lower. However, low data numbers make this result inconclusive. Insulin secretion was found to increase with BG, with a stronger association in female infants than males (R2=0.51 vs. R2=0.13, and R2=0.26 for the combined cohort). Conclusions: A sex-based insulin secretion model was created and incorporated into a model-based glycemic control framework. Nutritional intake did not predict insulin secretion, indicating that insulin secretion is a complex function of a number of metabolic factors