Age and geochemistry of the Charlestown Group, Ireland:Implications for the Grampian orogeny, its mineral potential and the Ordovician timescale

Accurately reconstructing the growth of continental margins during episodes of ocean closure has important implications for understanding the formation, preservation and location of mineral deposits in ancient orogens. The Charlestown Group of county Mayo, Ireland, forms an important yet understudied link in the Caledonian-Appalachian orogenic belt located between the well documented sectors of western Ireland and Northern Ireland. We have reassessed its role in the Ordovician Grampian orogeny, based on new fieldwork, high-resolution airborne geophysics, graptolite biostratigraphy, U–Pb zircon dating, whole rock geochemistry, and an examination of historic drillcore from across the volcanic inlier. The Charlestown Group can be divided into three formations: Horan, Carracastle, and Tawnyinah. The Horan Formation comprises a mixed sequence of tholeiitic to calc-alkaline basalt, crystal tuff and sedimentary rocks (e.g. black shale, chert), forming within an evolving peri-Laurentian affinity island arc. The presence of graptolites Pseudisograptus of the manubriatus group and the discovery of Exigraptus uniformis and Skiagraptus gnomonicus favour a latest Dapingian (i.e. Yapeenian Ya 2/late Arenig) age for the Horan Formation (equivalent to c. 471.2–470.5 Ma according to the timescale of Sadler et al., 2009). Together with three new U–Pb zircon ages of 471.95–470.82 Ma from enclosing felsic tuffs and volcanic breccias, this fauna provides an important new constraint for calibrating the Middle Ordovician timescale. Overlying deposits of the Carracastle and Tawnyinah formations are dominated by LILE- and LREE-enriched calc-alkaline andesitic tuffs and flows, coarse volcanic breccias and quartz-feldspar porphyritic intrusive rocks, overlain by more silicic tuffs and volcanic breccias with rare occurrences of sedimentary rocks. The relatively young age for the Charlestown Group in the Grampian orogeny, coupled with high Th/Yb and zircon inheritance (c. 2.7 Ga) in intrusive rocks indicate that the arc was founded upon continental crust (either composite Laurentian margin or microcontinental block). Regional correlation is best fitted to an association with the post-subduction flip volcanic/intrusive rocks of the Irish Caledonides, specifically the late-stage development of the Tyrone Igneous Complex, intrusive rocks of Connemara (western Ireland) and the Slishwood Division (Co. Sligo). Examination of breccia textures and mineralization across the volcanic inlier questions the previous porphyry hypothesis for the genesis of the Charlestown Cu deposit, which are more consistent with a volcanogenic massive sulfide (VMS) deposit.</p

Estimation of thermal conductivity and its spatial variability in igneous rocks from in situ density logging

Characterisation of thermal conductivity of rock and its spatial variability by laboratory measurements is costly and time-consuming. There is an incentive to find more cost-effective and rapid methods. A new empirical relationship between density and thermal conductivity for igneous rocks has been found. This paper explains that the relationship is based on the rock forming processes which in turn generate typical mineral compositions. Based on this relationship, thermal conductivity can be estimated from geophysical density loggings. Experience has shown that this indirect method of determining the thermal conductivity can be used to characterise the spatial variability of thermal conductivity for certain rock types. The spatial data can be used in the modelling of thermal rock domains. Applications of the statistical relationship are presented and illustrative examples are given of how spatial variability of thermal conductivity can be estimated, based on the site investigations in a crystalline bedrock environment in Sweden. Possible deficiencies of the method are identified, such as uncertainties associated with different rock forming minerals. Methods of improvement are also discussed

Optimising the management of malignant melanoma during COVID-19

The coronavirus disease 2019 (COVID-19) continues to present challenges for healthcare systems. This has resulted in the pragmatic restructuring of plastic surgery units worldwide1. This includes changes to leadership, staffing capabilities, redeployment and upskilling, adjustments to elective activity, and transformed patient pathways. In March 2020, all non-urgent elective surgery was cancelled across the UK and Ireland indefinitely2. It is estimated that over 28 million elective surgical procedures have been cancelled worldwide during the peak of the pandemic in both public and private practice. During this period, many units reported a significant fall in urgent melanoma referrals, which may lead to patients presenting with advanced disease, requiring more extensive surgery, and obtaining inferior long-term outcomes. The authors of this paper sought to characterise their own experience of invasive and non-invasive melanoma during the COVID-19 pandemic, with insights into our units restructuring to manage the disease continually and effectively.</div

Patients with Crohn's disease have longer post-operative in-hospital stay than patients with colon cancer but no difference in complications' rate

BACKGROUNDRight hemicolectomy or ileocecal resection are used to treat benign conditions like Crohn's disease (CD) and malignant ones like colon cancer (CC).AIMTo investigate differences in pre- and peri-operative factors and their impact on post-operative outcome in patients with CC and CD.METHODSThis is a sub-group analysis of the European Society of Coloproctology's prospective, multi-centre snapshot audit. Adult patients with CC and CD undergoing right hemicolectomy or ileocecal resection were included. Primary outcome measure was 30-d post-operative complications. Secondary outcome measures were post-operative length of stay (LOS) at and readmission.RESULTSThree hundred and seventy-five patients with CD and 2,515 patients with CC were included. Patients with CD were younger (median = 37 years for CD and 71 years for CC (P &lt; 0.01), had lower American Society of Anesthesiology score (ASA) grade (P &lt; 0.01) and less comorbidity (P &lt; 0.01), but were more likely to be current smokers (P &lt; 0.01). Patients with CD were more frequently operated on by colorectal surgeons (P &lt; 0.01) and frequently underwent ileocecal resection (P &lt; 0.01) with higher rate of de-functioning/primary stoma construction (P &lt; 0.01). Thirty-day post-operative mortality occurred exclusively in the CC group (66/2515, 2.3%). In multivariate analyses, the risk of post-operative complications was similar in the two groups (OR 0.80, 95%CI: 0.54-1.17; P = 0.25). Patients with CD had a significantly longer LOS (Geometric mean 0.87, 95%CI: 0.79-0.95; P &lt; 0.01). There was no difference in re-admission rates. The audit did not collect data on post-operative enhanced recovery protocols that are implemented in the different participating centers.CONCLUSIONPatients with CD were younger, with lower ASA grade, less comorbidity, operated on by experienced surgeons and underwent less radical resection but had a longer LOS than patients with CC although complication's rate was not different between the two groups