Timing of interplay between hydrothermal and surface fluids in the Navan Zn plus Pb orebody, Ireland: Evidence from metal distribution trends, mineral textures, and delta S-34 analyses

Models of genesis for the Navan orebody are of two distinct types. An early hypothesis that mesothermal (though nonmagmatic) deposition of ore began when a supernatant seawater brine still had access to the host sediments (during the early to mid-Mississippian), has been challenged by recent suggestions favoring a later (mid- to late Mississippian to Pennsylvanian) mineralization derived from the south. These models, characterized here as Irish-type and Mississippi Valley-type respectively, are interrogated as to their particular predictions with regard to metal distributions and sulfur isotope patterns associated with various fault geometries. The basal 5 lens of the Navan Zn + Pb deposit contains similar to70 percent of the known tonnage of the similar to90 Mt orebody and, thus, is the focus of this examination. Lead distribution patterns suggest that migration of metal-bearing fluids was principally directed up early to mid-Mississippian, near vertical north-northeast, northeast, and east-northeast minor normal faults. These faults predate or are coeval with the major extensional, partly listric, east- northeast fualts which now control the general disposition of the deposit. Only where these major east-northeast faults cross putative deep-seated northeast (Caledonoid) and northwest structures are they associated with lead enrichments. A systematic delta(34)S survey in the 5 lens across five minor north-northeast-through to east-northeast-trending faults associated with distinct lead enrichments, and one east- northeast-trending, partly listric, major extensional fault adjacent to that trend, revealed positive delta(34)S values (1- 18parts per thousand) for galena, sphalerite, and marcasite sampled within 3m of all the faults on the profile. Sulfides with positive delta(34)S values associated with the deep- seated, metal-bearing fluid generating the Navan deposit have been highlighted by previous workers (Anderson et al., 1998). The evidence reported here strongly suggests that the metal- bearing fluids rose through all the fractures. Conversely, negative delta(34)S values (-1 to -26parts per thousand) were returned in galena and sphalerite sampled 3 m or more from these faults. These negative values indicate that locally derived bacteriogenic sulfide, reduced from sea-water sulfate, dominated away from these faults. Pyrite delta(34)S values suggest a background level of -29 +/- 3.0 per mil across the profile. However, pyrite delta(34)S values as low as -34 +/- 2.7 per mil were recorded in one sample collected from within 1 m of a fault. Thus, fluids containing highly fractionated, bacteriogenic sulfide also gravitated into these faults on at least one occasion. There is also evidence suggesting that the metal-bearing solutions periodically displaced the locally derived bacteriogenic sulfide-bearing fluid in and near the faults. Mineral sulfide petrography is used to contextualize the sampling and to give a qualitative indication of the degree of chemical disequilibrium of the system. Mineral textures demonstrating comminution and dissolution are revealed by this study that, when coupled with evidence of isotopic overprinting, force the conclusion that mineralizing fluids first invaded the host lithologies during mid-Lower Mississippian times, coincident with active faulting. There is no evidence of reactivation of the minor fault sets encountered in the study area during post-Chadian tectonism, though the major, partly listric, east-northeast extensional faults were reactivated at that time. Ore deposition was effected by bacteriogenic sulfide (reduced from Mississippian seawater sulfate) reacting with rising, metal-bearing mesothermal fluids. Thus any model invoking an onset of mineralization later than the mid-Lower Mississippian does not stand up to this scrutiny

Metal enrichment trends within the Navan Zn plus Pb deposit: Indicators of feeder zones

No abstract available

The giant Navan Carbonate-hosted Zn-Pb deposit: a review

No abstract available

Zn, Fe and S isotope fractionation in a large hydrothermal system

The genesis of hydrothermal ore deposits is of crucial economic importance. This study investigates the extent, causes and consequences of zinc and iron isotope fractionation in a large hydrothermal system at the world-class Navan Zn–Pb orebody, Ireland. Large variations in Zn, Fe and S isotope compositions have been measured in microdrilled sphalerite (ZnS) at the millimetre scale. d66Zn and d56Fe display a well-defined positive correlation and both also correlate with d34S. These relationships represent the combined effects of kinetic Zn and Fe isotope fractionation during sphalerite precipitation, and S isotope variation through mixing of hot, metal-rich hydrothermal fluids and cool, bacteriogenic sulfide-bearing brines. Combined with S isotope data, d56Fe and d66Zn data on mine concentrates confirm that hydrothermal sulfide is a minor component of the overall deposit signature. Our data suggest that incoming pulses of metal-rich hydrothermal fluid triggered sulfide mineralisation, and that rapid precipitation of sphalerite from hydrothermal fluids will lead to strong kinetic fractionation of Zn and Fe isotopes at very short time and length scales, thereby limiting the use of Fe and Zn isotopes as exploration tools within deposits, but revealing the possibility of detecting new deposits from isotopically heavy Zn–Fe geochemical halos.Science Foundation IrelandDG 16/10/201

Reduction of incidence and severity of Septoria lycopersici leaf spot of tomato with bacteria and yeasts Redução da incidência e severidade da mancha foliar do tomateiro causada por Septoria lycopersici com bacteria e leveduras

Septoria leaf spot, caused by Septoria lycopersici, is an important disease of tomato (Lycopersicon esculentum) which is mainly controlled by fungicide sprays. One of the alternatives to reduce fungicide applications is the use of leaf antagonists such as yeast and bacterium. This study was conducted from 1994 through 1995 in Auburn, AL, USA. The pathogen and one antagonist were isolated from field plants. In greenhouse, six yeast and one bacterial isolates were tested, in a set of seven experiments. The experiments were conducted in a completely randomized design with four to eight treatments and six replications. The antagonists (1-3 × 10(8) colony forming units ml-1) were inoculated 48h before the inoculation of the pathogen (1-2 × 10(5) conidia ml-1), under conditions of intermittent misting. The yeast isolate Y236 (Cryptococcus laurentii) and the bacterial isolate BTL (Pseudomonas putida) significantly (P <= 0.05) reduced the incidence or the severity of the disease in most experiments.<br>A mancha foliar causada pelo fungo Septoria lycopersici é uma doença no tomateiro (Lycopersicon esculentum), controlada basicamente pela aplicação de fungicidas. Uma das alternativas ao controle químico dessa enfermidade é a utilização de bactérias e leveduras antagonistas. Este estudo foi conduzido de 1994 a 1995 em Auburn, Alabama, EUA. O patógeno e um dos antagonistas foram isolados do filoplano de plantas de tomateiro infectadas pela doença em questão. Sete antagonistas (um isolado de bacteria e seis de leveduras) foram testados em uma série de sete experimentos conduzidos em casa de vegetação. Os experimentos foram conduzidos em um delineamento completamente casualizado com quatro a oito tratamentos e seis repetições. Em todos os experimentos, os antagonistas (1-3 × 10(8) unidades formadoras de colonia ml-1) foram inoculados 48h antes da inoculação com o patógeno (1-2 × 10(5) conidios ml-1), sob condições de nebulosidade intermitente. Entre os antagonistas testados, destacaram-se o isolado de levedura Y236 (Cryptococcus laurentii) e o isolado bacteriano BTL (Pseudomonas putida). Ambos os isolados reduziram significativamente (P <= 0.05) a incidência e a severidade da doença na maioria dos experimentos

Relationship between quality of care, staffing levels, skill mix and nurse autonomy: literature review

AimsThis paper reports a literature review exploring the relationship between quality of care and selected organizational variables through a consideration of what is meant by perceptions of quality, whose perceptions are accorded prominence, and whether changes in staffing, skill mix and autonomy affect perceptions of quality.BackgroundThree basic ideas underpin this literature review: the growing focus on quality improvement in health care, concerns about the quality of care, and the move towards patient involvement and consultation. Of particular interest is the way in which changes in nurse staffing, skill mix and autonomy may affect the delivery of quality patient care.MethodsA search was conducted using the CINAHL, Medline and Embase databases. Key words used were quality of health care; quality of nursing care; nurse; patient; skill mix; nurse-patient ratio; outcomes; adverse health care events and autonomy. The objective was to draw together a diverse collection of literature related to the field of health care quality. Papers were included for their relevance to the field of enquiry. The original search was conducted in 2003 and updated in 2004.FindingsQuality of care is a complex, multi-dimensional concept which presents researchers with a challenge when attempting to evaluate it. Traditional nursing assessment tools have fallen out of use, partly because they have failed to provide opportunities to engage with and access the views of patients or nurses. There is also evidence that patient satisfaction as an indicator of quality is compromised on a number of fronts. There is conflicting information on how nurses and patients think about quality. Research looking at the relationship between the selected organizational variables and perceptions of quality also suffers from a number of limitations. We argue that there is a requirement for more patient-centred research exploring perceptions of quality and differences in nurse staffing, skill mix and autonomy.Veronica Currie, Gill Harvey, Elizabeth West, Hugh McKenna, Sinead Keene