Tara Deep zinc-lead deposit in Navan, Co. Meath, Ireland: ore and carbonate depositional processes

The Tara Deep Zn-Pb deposit (currently 26.2 Mt @ 8.4% Zn, 1.6% Pb) is the latest major discovery by Boliden Tara Mines (first announced in 2016) which significantly adds to the existing world-class Navan deposit. Located 2 km south of the Navan deposit in Co. Meath, Ireland, economic mineralization is hosted by upper Tournaisian carbonates (Pale Beds; 87% of the total economic resource), within a degraded footwall of a major south-dipping normal fault, and also within lower Viséan sedimentary breccias (S Fault Conglomerates; 13% of the total economic resource). Sphalerite and galena are the dominant sulfides, with massive, cavity fill and brecciated textures dominating. These textures attest complex, subsurface, episodic mineralization events that display considerable reworking, fracturing, dolomitization, open-space infill and selective replacement. Lower Viséan syn-rift sliding, erosion, and deposition of thick debrites and calc-turbidites at Tara Deep record basin margin processes near extensional faulting associated with formation of the Dublin Basin. These sedimentary breccias host detrital sulfide-rich clasts and offer unambiguous evidence that the onset of mineralization occurred during the upper Tournaisian. Conventionally drilled 34S values of base metal sulfides have a bimodal distribution suggesting both bacteriogenic (-13.5 to -3.6 ‰) and hydrothermal sulfur sources (+3.4 to +16.2 ‰). Both textural and sulfur isotope data reveal the dynamic nature of mineralization at Tara Deep and infer fluid mixing. Conventional lead isotope analyses display remarkably homogenous 206Pb/204Pb of 18.23±0.006 (2σ, n=25), which is consistent with Pb isotope data across the Navan deposit. Subsequently, Tara Deep and Navan are isotopically similar, showing both a statistically identical Pb isotopic signature and a bimodal sulfide S isotopic distribution and homogeneous sulfate signature. In particular, the Pb isotopes and the hydrothermal S signature, correlate with Navan and agree that base metals were leached from the underlying Lower Palaeozoic basement, this suggests that similar deep, circulating metalliferous fluids were also involved at Tara Deep. However, despite these similarities, key differences can be recognized within the S isotope data; around 5‰ shifts to higher 34S in the surface-derived S isotope signatures (both bacteriogenic sulfide and sulfate) indicate that Tara Deep’s sulfur was sourced from a distinct seawater/connate fluid signature. Floatation concentrate samples were obtained on representative drillholes from across the Tara Deep deposit by Boliden Tara Mines’ laboratory to inform recovery data for future financial modelling. The concentrates produced were analysed for S and Pb isotopes. The samples reveal limited variation with mean δ34S = -6 ± 5.9 ‰ (n = 38), and galena concentrate mean 206Pb/204Pb=18.22 ± 0.004 (n = 19). Mass balance calculations suggest that ~90 percent of the Tara Deep sulfides were derived from bacteriogenic reduction of contemporaneous Lower Carboniferous seawater sulfate. In contrast, metals were acquired from a local, orogenic crustal source beneath the orebody. These concentrate isotopic signatures differ from those associated with the Main Navan Orebody, in particular the bacteriogenic mode, reiterating that Tara Deep should be considered as an isolated deposit in space, and potentially time, and not an allochthonous block of the Navan deposit. As was reported for the world-class Navan deposit, enhanced bacterial activity was fundamental to ore deposition at Tara Deep, providing significant reassurance for continuing exploration. Tara Deep is located at depths of between 1.2-1.9 km within fault-controlled terraces on the degraded footwall of a major normal fault system. The system formed as a result of a rapidly subsiding basin margin during the upper Tournaisian extension. The region’s long lived and dynamic evolution has resulted in a complex architecture of large normal and strike slip faults. The complexity of the Dublin Basin margin evolution at Navan can be divided into three distinct phases: pre-rift ramp sedimentation in the Lower Carboniferous (Mississippian), syn-rift abrupt detachment and destructive debris flows in the lower Viséan, and finally late-rift basin infill during the Viséan. Diagenetic processes include dolomitization, mineralization and extensive pressure solution, which complicate the lithofacies reconstruction by occluding pre-existing textures. Dolomitization occurs in four phases: D1 – D4. D1 predates mineralization and represents early replacement by non-ferroan euhedral dolomite (30 μm), this dolomite typically has cloudy cores (often associated with Mn), with clear ferrous rims. D2 represents interparticle infill by anhedral (50 μm) ferroan dolomite. D3 occurs as late, coarse, non-ferroan saddle dolomite cement which occurs in vugs. D4 occurs as the last phase throughout the Tara Deep succession, is nanocrystalline, and is related to burial dolomitization witnessed by its close association with pressure solution seams. Pressure solution is extensive at Tara Deep and is partially responsible for the generation of common and distinct stylo-nodular textures in the Pale Beds, and can also lead to occlusion of the original host rock fabric in the Thin Bedded Unit. Oxygen and carbon isotopes are used to constrain these interpretations. Mineralization is also intimately linked to basin margin development and architecture and is recorded across early syn-rifting textures to late-rifting textures, highlighting the complexity and longevity of the mineralizing system within the Lower Carboniferous (Mississippian) carbonates. Together these processes speak of a dynamic sedimentary, tectonic, and microbiological environment which has culminated in an exceptional accumulation and preservation of base metals during the Lower Carboniferous. Mineralization initiated during an early phase of the developing Dublin Basin (syn-diagenetically) and kept pace with rifting and subsequently an evolving basin. The Tara Deep deposit has many similarities with the neighbouring Navan deposit reflecting comparable controls on the mineralizing processes in terms of host rocks, Pb and S sources, and tectonic environment

Petrogenesis and geochemical halos of the amphibolite facies, Lower Proterozoic, Kerry Road volcanogenic massive sulfide deposit, Loch Maree Group, Gairloch, NW Scotland

The Palaeoproterozoic Kerry Road deposit is one of the oldest examples of volcanogenic massive sulfide (VMS) mineralization. This small VMS deposit (~500,000 tons grading at 1.2% Cu, 3.5% Zn) is hosted in amphibolite facies mafic-siliciclastic units of the c. 2.0 Ga Loch Maree Group, Scotland. Sulfide mineralization consists of pyrite and pyrrhotite with subordinate chalcopyrite and sphalerite, occurring in disseminated, vein and semi-massive to massive textures. The deposit was highly deformed and metamorphosed during the c. 1.8–1.7 Ga Laxfordian Orogeny. Textural relationships of deformed sulfide minerals, related to early Laxfordian deformation (D1/D2), indicate initial high pressure-low temperature (100 MPa, 150 °C) conditions before reaching peak amphibolite facies metamorphism, as evident from pyrrhotite crossing the brittle/ductile transition prior to chalcopyrite. Late Laxfordian deformation (D3/D4) is marked by local retrograde greenschist facies at low pressure and temperature (<1.2 MPa, <200 °C), recorded by late red sphalerite remobilization. δ34S values from all sulfide minerals have a homogeneous mean of 0.8 ± 0.7‰ (n = 21), consistent with interaction of hydrothermal fluids in the host oceanic basalt-island arc setting envisaged for deposition of the Loch Maree Group. Microprobe analyses of amphiboles record evidence of the original alteration halo associated with the Kerry Road deposit, with a systematic Mg- and Si- enrichment from ferrotschermakite (~150 m) to Mg-hornblende (~90 m) to actinolite (0 m) on approach to the VMS deposit. Furthermore, whole rock geochemistry records a progressive enrichment in Si, Cu, Co, and S, and depletion in Al, Ti, V, Cr, Y and Zr with proximity to the VMS system. These elemental trends, together with amphibole geochemistry, are potentially useful exploration vectors to VMS mineralization in the Loch Maree Group, and in similar highly deformed and metamorphosed terranes elsewhere.PostprintPeer reviewe

The Dawn of Open Access to Phylogenetic Data

The scientific enterprise depends critically on the preservation of and open access to published data. This basic tenet applies acutely to phylogenies (estimates of evolutionary relationships among species). Increasingly, phylogenies are estimated from increasingly large, genome-scale datasets using increasingly complex statistical methods that require increasing levels of expertise and computational investment. Moreover, the resulting phylogenetic data provide an explicit historical perspective that critically informs research in a vast and growing number of scientific disciplines. One such use is the study of changes in rates of lineage diversification (speciation - extinction) through time. As part of a meta-analysis in this area, we sought to collect phylogenetic data (comprising nucleotide sequence alignment and tree files) from 217 studies published in 46 journals over a 13-year period. We document our attempts to procure those data (from online archives and by direct request to corresponding authors), and report results of analyses (using Bayesian logistic regression) to assess the impact of various factors on the success of our efforts. Overall, complete phylogenetic data for ~60% of these studies are effectively lost to science. Our study indicates that phylogenetic data are more likely to be deposited in online archives and/or shared upon request when: (1) the publishing journal has a strong data-sharing policy; (2) the publishing journal has a higher impact factor, and; (3) the data are requested from faculty rather than students. Although the situation appears dire, our analyses suggest that it is far from hopeless: recent initiatives by the scientific community -- including policy changes by journals and funding agencies -- are improving the state of affairs

Systematically reviewing and synthesizing evidence from conversation analytic and related discursive research to inform healthcare communication practice and policy: an illustrated guide

Background Healthcare delivery is largely accomplished in and through conversations between people, and healthcare quality and effectiveness depend enormously upon the communication practices employed within these conversations. An important body of evidence about these practices has been generated by conversation analysis and related discourse analytic approaches, but there has been very little systematic reviewing of this evidence. Methods We developed an approach to reviewing evidence from conversation analytic and related discursive research through the following procedures: • reviewing existing systematic review methods and our own prior experience of applying these • clarifying distinctive features of conversation analytic and related discursive work which must be taken into account when reviewing • holding discussions within a review advisory team that included members with expertise in healthcare research, conversation analytic research, and systematic reviewing • attempting and then refining procedures through conducting an actual review which examined evidence about how people talk about difficult future issues including illness progression and dying Results We produced a step-by-step guide which we describe here in terms of eight stages, and which we illustrate from our ‘Review of Future Talk’. The guide incorporates both established procedures for systematic reviewing, and new techniques designed for working with conversation analytic evidence. Conclusions The guide is designed to inform systematic reviews of conversation analytic and related discursive evidence on specific domains and topics. Whilst we designed it for reviews that aim at informing healthcare practice and policy, it is flexible and could be used for reviews with other aims, for instance those aiming to underpin research programmes and projects. We advocate systematically reviewing conversation analytic and related discursive findings using this approach in order to translate them into a form that is credible and useful to healthcare practitioners, educators and policy-makers

Fracture in the Elderly Multidisciplinary Rehabilitation (FEMuR): study protocol for a phase II randomised feasibility study of a multidisciplinary rehabilitation package following hip fracture

Objective: To conduct a rigorous feasibility study for a future definitive parallel-group randomised controlled trial (RCT) and economic evaluation of an enhanced rehabilitation package for hip fracture.Setting: Recruitment from 3 acute hospitals in North Wales. Intervention delivery in the community.Participants: Older adults (aged ≥65) who received surgical treatment for hip fracture, lived independently prior to fracture, had mental capacity (assessed by clinical team) and received rehabilitation in the North Wales area.Intervention: Remote randomisation to usual care (control) or usual care+enhanced rehabilitation package (intervention), including six additional home-based physiotherapy sessions delivered by a physiotherapist or technical instructor, novel information workbook and goal-setting diary.Primary and secondary outcome measures: Primary: Barthel Activities of Daily Living (BADL). Secondary measures included Nottingham Extended Activities of Daily Living scale (NEADL), EQ-5D, ICECAP capability, a suite of self-efficacy, psychosocial and service-use measures and costs. Outcome measures were assessed at baseline and 3-month follow-up by blinded researchers.Results: 62 participants were recruited, 61 randomised (control 32; intervention 29) and 49 (79%) completed 3-month follow-up. Minimal differences occurred between the 2 groups for most outcomes, including BADL (adjusted mean difference 0.5). The intervention group showed a medium-sized improvement in the NEADL relative to the control group, with an adjusted mean difference between groups of 3.0 (Cohen's d 0.63), and a trend for greater improvement in self-efficacy and mental health, but with small effect sizes. The mean cost of delivering the intervention was £231 per patient. There was a small relative improvement in quality-adjusted life year in the intervention group. No serious adverse events relating to the intervention were reported.Conclusions: The trial methods were feasible in terms of eligibility, recruitment and retention. The effectiveness and cost-effectiveness of the rehabilitation package should be tested in a phase III RCT

Effects of fluoxetine on functional outcomes after acute stroke (FOCUS): a pragmatic, double-blind, randomised, controlled trial

Background Results of small trials indicate that fluoxetine might improve functional outcomes after stroke. The FOCUS trial aimed to provide a precise estimate of these effects. Methods FOCUS was a pragmatic, multicentre, parallel group, double-blind, randomised, placebo-controlled trial done at 103 hospitals in the UK. Patients were eligible if they were aged 18 years or older, had a clinical stroke diagnosis, were enrolled and randomly assigned between 2 days and 15 days after onset, and had focal neurological deficits. Patients were randomly allocated fluoxetine 20 mg or matching placebo orally once daily for 6 months via a web-based system by use of a minimisation algorithm. The primary outcome was functional status, measured with the modified Rankin Scale (mRS), at 6 months. Patients, carers, health-care staff, and the trial team were masked to treatment allocation. Functional status was assessed at 6 months and 12 months after randomisation. Patients were analysed according to their treatment allocation. This trial is registered with the ISRCTN registry, number ISRCTN83290762. Findings Between Sept 10, 2012, and March 31, 2017, 3127 patients were recruited. 1564 patients were allocated fluoxetine and 1563 allocated placebo. mRS data at 6 months were available for 1553 (99·3%) patients in each treatment group. The distribution across mRS categories at 6 months was similar in the fluoxetine and placebo groups (common odds ratio adjusted for minimisation variables 0·951 [95% CI 0·839–1·079]; p=0·439). Patients allocated fluoxetine were less likely than those allocated placebo to develop new depression by 6 months (210 [13·43%] patients vs 269 [17·21%]; difference 3·78% [95% CI 1·26–6·30]; p=0·0033), but they had more bone fractures (45 [2·88%] vs 23 [1·47%]; difference 1·41% [95% CI 0·38–2·43]; p=0·0070). There were no significant differences in any other event at 6 or 12 months. Interpretation Fluoxetine 20 mg given daily for 6 months after acute stroke does not seem to improve functional outcomes. Although the treatment reduced the occurrence of depression, it increased the frequency of bone fractures. These results do not support the routine use of fluoxetine either for the prevention of post-stroke depression or to promote recovery of function. Funding UK Stroke Association and NIHR Health Technology Assessment Programme

How Long Does It Take to Form a Sediment Hosted Zn Plus Pb Deposit?

Sediment hosted Zn+Pb sulphide deposits are the primary source of global lead and zinc. Their secular distribution is well defined, however the duration of individual mineralisation events is less so. By coupling modern H2S production data from sedimentary/hydrothermal environments and metalliferous fluid flux calculations with data on the size concentration and distribution of the world class Navan Zn-Pb deposit in Ireland, it is postulated that the deposit could have formed within a relatively rapid, integrated timeframe of similar to 26,000 years. Ore fluid influx, driven by convection and seismicity, is assumed to be the most limiting factor. In this study, bacteriogenic sulphide availability is not considered to be a limiting factor