The Tara Deep Zn-Pb deposit, at Navan, Ireland, includes sub-economic pyrite-rich mineralization extending laterally for about 2 × 2 km within the overlying Lower Viséan calc-turbidites, known as the 'New-Thin Bedded Unit'. Here, we investigate the genesis of this pyritic mineralization and its links to the limestone-hosted Zn-Pb deposit lying 100 m below it. Four mineral assemblages have been identified: 1) in black shales, laminated pyrite comprises thin framboid-rich layers with minor interstitial sphalerite, both showing variable but low δ34S values ranging from −37.4 to 3.3‰; 2) in calcarenite and calcsiltite layers, pyritized fossils are widely distributed and occur chiefly as biodebris replaced by low δ34S pyrite (mean values of −13.2‰); 3) a replacive assemblage occurs as late remobilizations exhibiting both crosscutting and bedding-parallel styles, overprinting the early laminated pyrite. It comprises mostly of marcasite, with minor pyrite, sphalerite, chalcopyrite, galena, stibnite and Co-pentlandite, with high δ34S values up to 24.5‰; and 4) in black shales, bedded sulfide-rich cherts comprising microcrystalline quartz lenses exhibit δ18O mean values of 25.3‰. Cherts are rimmed by dolomite, associated with marcasite, pyrite, sphalerite, chalcopyrite, galena, siegenite and stibnite also with high δ34S values up to 44.2‰. In general terms, pyrite shows a relatively high Co/Ni ratio > 1 and sphalerite Zn/Cd ratios vary from 268 to 364. Textural analysis indicates overlapping of early-diagenetic and multi-phase hydrothermal sulfide mineralization. Development of laminated pyrite and pyritized calcarenites suggests that this mineralization was generated during early diagenesis, close to the seawater-sediment interface in oxygen-poor conditions under the influence of low-temperature hydrothermal fluid circulation. Later hydrothermal cherts and replacive sulfides suggest discharge of relatively warm hydrothermal fluids during early to mid-diagenesis, presumed to be linked to movements of nearby normal faults. Similarities in mineralogy and S isotope compositions suggest genetic links between the sub-economic pyritic mineralization and the underlying Tara Deep deposit, and consequently, that the former represents a geochemical halo with direct applicability in exploration for Zn-Pb deposits.
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 Tour-naisian carbonates (Pale Beds; 87% of the total economic resource), within a degraded footwall of a major south-dipping normal fault, and also within lower Visean sedimentary breccias (‘S Fault’ Conglomerates; SFC). Sphalerite and galena are the dominant sulphides, 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 Visean 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 debrites host detrital sulphide-rich clasts and offer unambiguous evidence that the onset of mineralization occurred during the upper Tournaisian. δ34S values of base metal sulphides have a bimodal distribution suggesting both bacteriogenic (-13.5 to -3.6‰) and hydrothermal sulphur sources (+3.4 to +16.2‰). Both textural and sulphur isotope data reveal the dynamic nature of mineralization at Tara Deep and infer fluid mixing. Lead isotope analyses display remarkably homogeneous 206Pb/204Pb of 18.23 ±0.006 (2σ, n=25), which is coincident 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 sulphide S isotopic distribution and homogeneous sulphate signature. In particular, the Pb isotopes and the hydrothermal S signature, correlate with Navan and support the view that base-metals were leached from the underlying Lower Palaeozoic basement, and suggest 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 δ34S in the surface-derived S isotope signatures (both bacteriogenic sulphide and sulphate) indicate that Tara Deep’s sulphur was sourced from a distinct seawater/connate fluid signature. 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. Mineralization initiated during an early phase of the developing Dublin Basin (syn-diagenetically) and kept pace with rifting and subsequently an evolving basin.
Irish-type deposits comprise carbonate-hosted sphalerite- and galena-rich lenses concentrated near normal faults. We present new data from the Tara Deep resource and overlying mineralization, at Navan, and the Island Pod deposit and associated Main zone orebodies, at Lisheen. Tara Deep mineralization predominantly replaces Tournasian micrites and subordinate Visean sedimentary breccias. The mineralization is mainly composed of sphalerite, galena, marcasite and pyrite. A range of Cu- and Sb-bearing minerals occur as minor phases. At Tara Deep, paragenetically early sulfides exhibit negative δ34S values, with later phases displaying positive δ34S values, indicating both bacterial sulfate reduction (BSR) and hydrothermal sulfur sources, respectively. However, maximum δ34S values are heavier (25‰) than in the Main Navan orebody (17‰). These mineralogical and isotopic features suggest that Tara Deep represents near-feeder mineralization relative to the Navan Main orebody. The subeconomic mineralization hosted in the overlying Thin Bedded Unit (TBU) comprises sphalerite replacing framboidal pyrite, both exhibiting negative δ34S values (−37.4 to −8.3‰). These features indicate a BSR source of sulfur for TBU mineralization, which may represent seafloor exhalation of mineralizing fluids that formed the Tara Deep orebody. The Island Pod orebody, at Lisheen, shows a mineralogical paragenetic sequence and δ34S values broadly similar to other Lisheen orebodies. However, the lack of minor Cu, Ni, and Sb minerals suggests a setting more distal to hydrothermal metal feeder zones than the other Lisheen orebodies. Pb isotope data indicate a very homogeneous Lower Palaeozoic Pb source for all Navan orebodies. Lower Palaeozoic metal sources are also inferred for Lisheen, but with variations both within and between orebodies. Carbon and oxygen isotopic variations at Navan and Lisheen appear to result from fluid-carbonate rock buffering. The emerging spectrum of mineralogical and isotopic variations define proximal to distal characteristics of Irish-type systems and will assist in developing geochemical vectoring tools for exploration.
Abstract In the first decade of the 21st century, surface exploration drilling around the Boliden Tara mine at Navan, Ireland, aimed at ~1-km-deep targets, was becoming ineffective. During 2010, the extensive geologic knowledge of the existing Navan orebody was leveraged in an Experts Meeting to promote near-mine discovery. Two ideas, of many, were of relevance to this paper: (1) undiscovered mineralized fault-related zones were predicted south of the orebody, and (2) seismic surveys could locate subsurface faults. By late 2012, seven 2D seismic lines (totaling 101 km) had been acquired, processed, and initially interpreted. Pre-stack time migration images were used for interpretation, augmented by diamond drill core data where available. The seismic imaging proved a “game changer” in terms of subsurface visualization and a priority target was identified 2 km south of the mine on the footwall crest of a large south-dipping basin-margin fault. The first hole intersected 34 m of mineralized rock with 14% Zn + Pb, but at greater depth than anticipated. Follow-up drilling was initially successful but proved to be challenging. The first hole intersected a deep structurally complex section of the newly discovered zone that required more drilling to establish its location and attitude. Further drilling, utilizing extensive navigational deflection technology, outlined a mineralized zone similar in nature to the Navan 5 Lens at depths of 1 to 2 km. Inferred resources through 2016 were estimated at 10.2 Mt grading 8.5% Zn and 1.8% Pb. Underground exploration development of this zone commenced in April 2017, and will allow accurate delineation of this significant discovery.
ABSTRACT Pneumonia is a common cause for intensive care unit (ICU) admission for breathing support from a mechanical ventilator, resulting in high morbidity, mortality, and healthcare costs. Physiotherapists working in ICU treat patients with critical pneumonia using a range of respiratory treatments to improve breathing, hasten weaning from the ventilator, and restore functional independence. Evidence supports the short-term benefits of these treatments, however currently no standard of physiotherapy practice exists for these ICU patients. Despite a plethora of studies which have shown that physiotherapy treatments, such as ventilator lung hyperinflation (VHI), aid the lungs to work better short-term, there are no studies to date which investigate the effect of these important treatments on meaningful patient-important outcomes, such as earlier weaning from the ventilator, earlier hospital discharge, less breathlessness and lung secretions, short- and longer-term disability, health- related quality of life and survival. Through previous multiphase mixed-methods research, a clinical practice guideline was developed outlining best physiotherapy practice for this ICU patient cohort. This proposed research involves conducting a multicentre hybrid implementation-effectiveness randomised, controlled trial which aims to: evaluate implementation of physiotherapy guideline care for management of pneumonia in ICU regarding feasibility, safety and acceptability; and to determine the safety and effectiveness of a standardised dosage of daily ventilator hyperinflation in addition to standard guideline care on patient-important outcomes, health system outcomes; and cost effectiveness. This study will address critical knowledge gaps in the ICU physiotherapy evidence base regarding the impact of a course of standardised, best practice respiratory physiotherapy intervention during the ICU stay for patients with critical pneumonia requiring invasive mechanical ventilation, provide valuable information for clinicians to inform clinical practice regarding treatable traits and streamlining care to promote clinical efficiency, and determine the impact of respiratory physiotherapy care on patient-important and health service outcomes. Trial registration ANZ Clinical trials Registry number ACTRN12624001130550.
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