The genesis and tectonic significance of chromitite-bearing serpentinites in southern NSW

University of Technology, Sydney. Faculty of Science.The Tumut Serpentinite Province consists of four major serpentinite belts and numerous small serpentinite bodies, that occupy a long narrow tract within the Lachlan Fold Belt of southern NSW. The tectonic setting of one belt, the Coolac Serpentinite Belt, has been contentious. Much of the uncertainty results from lack of a combined study on the major belts and inadequate age constraints. Resolving the uncertainty will benefit construction of a tectonic model for the evolution of the Lachlan Fold Belt. The belts mainly comprise massive serpentinite or harzburgite, with internal shear zones of schistose serpentinite, and intrusions of plagiogranite, gabbro, basalt, pyroxenite, dunite and chromitite. The main foliation has a consistent NNW-SSE trend and is similar in the adjacent rock units. The various rock types of the serpentinite belts are geochemically akin to similar rocks from ophiolite sequences. Podiform chromitites are geochemically, mineralogically and geometrically akin to those in the mantle sequence ofmost ophiolites. The different chromitite types are interpreted in tenns of the degree of evolution of the MORB-type magma and hence the extent of fractionation ofthe source. Serpentinisation and rodingitisation occurred during progressive cooling of the chromitites and host rocks and were accompanied by systematic fracturing and remobilisation of chemical components. Radioisotope dating gives an age of crystallisation of41Z-400 Ma for the plagiogranites and leucogabbros, whilst an inherited zircon age of 430 Ma appears to be derived from Early Silurian felsic volcanic rocks of the region. As the plagiogranites, leucogabbros and other rock types within the serpentinite belts have common deformational and metamorphic histories, their crystallisation age constrains the ages of deformation and metamorphism. The serpentinite belts are interpreted as ophiolites of the 'embryonic' type that formed within a back-arc basin setting in the Late Silurian-Early Devonian. Crystallisation of the MORB sequence and emplacement onto continental crust, together with metamorphism and deformation may have only spanned 20 Ma. In the Late Silurian to Early Devonian, the Tumut Serpentinite Province differed from basins elsewhere within the Lachlan Fold Belt in.that a volcanic arc was ruptured by mantle-derived MORB magmas which ascended to the stuface. Their extrusion was short-lived and after the Early Devonian, the development of the Tumut region differed little from that in the rest of the Lachlan Fold Belt. The development of oceanic crust within the Tumut Serpentinite Province and the generation of granitic magmas within the central and eastern parts of the Lachlan Fold Belt are symptomatic of the same Late Silurian to Early Devonian tectonothennal event. An important aspect of this is that oceanic and crustal rocks need not fonn from different events or in substantially different tectonic settings

The Tamar Trough revisited: correlations berween sedimentary beds, basalts, their ages and valley evolution, North Tasmania

The Tamar Trough, an Early Palaeogene fault structure, contains sedimentaty beds and interleaved basaltic flows that infill the structure along its 70 km length. These infills represent a complex interplay between sedimentation, channel erosion, eruptive dislocations, and even 'out of trough' diyersions of the ancestral Tamar drainage. Several areas of resistant basalt flows remain in the south, upper, middle and lower Tamar reaches. Although some palynological control was known, radiometric dating of previously untested basalts now allows close integration and age-pegging for observed palynological biozones. The K-Ar and Ar-Ar ages of the basalt bodies indicate eruptive events at 47, 33-37 and 25 Ma, correlating with Proteacidites asperopolus-Malvacipollis diversus, Nothofagites asperus and Proteacidites tuberculatus biozone age sedimentary beds respectively. Basanite, alkali basalt and hawaiite flows dominate basalt lithology with lesser olivine nephelinite, transitional olivine basalt, olivine tholeiite and quartz tholeiite. Basalt geochemistry suggests derivation from different degrees of partial mande melting (from 7 to 35%), with alkaline and tholeiitic basalts being derived from separate source regions. Most alkaline basalts have high-jl (HIMU) related trace element signatures, which are absent in the tholeiitic rocks. A basalt plug on the trough margin at Loira gave a Jurassic age and has Jurassic dolerite-like geochemistry. The Tamar sequence suggests that the initial fluvio-Iacustrine and later channel-fill sedimentation from 65(?) to 24(?) Ma was then punctuated in places by periods of alkaline volcanism between 47 to 33(?) Ma, and alkaline and tholeiitic volcanism between 33 to 24(?) Ma. No Neogene fossils are known, so this later period was probably one of net erosion. These contrasting quiet sedimentary and more volcanic intervals are related here to a tectonic model that involves northerly drift of Victorian and Tasmanian lithosphere over several former Tasman metasomatised mantle plume sources

Behaviour of carbon-14 containing low molecular weight organic compounds in contaminated groundwater under aerobic conditions

Short chain carbon-14 (14C) containing organic compounds can be formed by abiotic oxidation of carbides and impurities within nuclear fuel cladding. During fuel reprocessing and subsequent waste storage there is potential for these organic compounds to enter shallow subsurface environments due to accidental discharges. Currently there is little data on the persistence of these compounds in such environments. Four 14C labelled compounds (acetate; formate; formaldehyde and methanol) were added to aerobic microcosm experiments that contained glacial outwash sediments and groundwater simulant representative of the Sellafield nuclear reprocessing site, UK. Two concentrations of each electron donor were used, low concentration (10-5 M) to replicate predicted concentrations from an accidental release and high concentration (10-2 M) to study the impact of the individual electron donor on the indigenous microbial community in the sediment. In the low concentration system only ~5% of initial 14C remained in solution at the end of experiments in contact with atmosphere (250-350 hours). The production of 14CO2(g) (measured after 48 hours) suggests microbially mediated breakdown is the primary removal mechanism for these organic compounds, although methanol loss may have been partially by volatilisation. Highest retention of 14C by the solid fractions was found in the acetate experiment, with 12% being associated with the inorganic fraction, suggesting modest precipitation as solid carbonate. In the high concentration systems only ~5% of intial 14C remains in solution at the end of the experiments for acetate, formate and methanol. In the formaldehyde experiment only limited loss from solution was observed (76% remained in solution). The microbial populations of unaltered sediment and those in the low concentration experiments were broadly similar, with highly diverse bacterial phyla present. Under high concentrations of the organic compounds the abundance of common operational taxonomic units was reduced by 66% and the community structure was dominated by Proteobacteria (particularly Betaproteobacteria) signifying a shift in community structure in response to the electron donor available. The results of this study suggest that many bacterial phyla that are ubiquitous in near surface soils are able to utilise a range of 14C-containing low molecular weight organic substances very rapidly, and thus such substances are unlikely to persist in aerobic shallow subsurface environments

Coprecipitation of 14C and Sr with carbonate precipitates: The importance of reaction kinetics and recrystallization pathways

This study investigated the simultaneous removal of Sr2+ and 14CO32- from an alkaline (pH >12) Ca(OH)2 solution by the precipitation of calcium carbonate. Initial Ca2+:CO32- ratios ranged from 10:1 to 10:100 (mM: mM). Maximum removal of 14C and Sr2+ both occurred in the system containing 10 mM Ca2+ and 1 mM CO32- (99.7% and 98.6% removal, respectively). A kinetic model is provided that describes 14C and Sr removal in terms of mineral dissolution & precipitation reactions. The removal of 14C was achieved during the depletion of the initial TIC in solution, and was subsequently significantly affected by recrystallization of a calcite precipitate from an elongate to isotropic morphology. This liberated >46% of the 14C back to solution. Sr2+ removal occurred as Ca2+ became depleted in solution and was not significantly affected by the recrystallization process. This reaction could form the basis for low cost remediation scheme for 90Sr and 14C in radioactively contaminated waters (<$0.25 reagent cost per m3 treated)

In situ disposal of crushed concrete waste as void fill material at UK nuclear sites: Leaching behavior and effect of pH on trace element release

The leaching behavior of stockpiled crushed concrete waste is important in determining its suitability for in situ disposal at UK nuclear sites. Sand sized particles from surface (0–0.1 m) and subsurface (2.5–2.7 m) samples were composed of silica and calcite grains in a matrix of calcium alumina-silicate hydrate (C-(A)-S-H) with Ca/Si ratios of 0.5 ±0.3 and 0.9 ±0.3 respectively. Calcite content was also higher in surface samples indicating a greater degree of weathering and carbonation. This resulted in lower leachate pH for the surface samples (pH 8–9.6) compared to subsurface samples (pH 10–11.3). The waste displayed a high acid buffering capacity but low alkaline buffering capacity. Element release as a function of pH was similar for surface and sub-surface samples and between different size fractions. Leaching of contaminant metals was close to minimum values at the pH values produced by the crushed concrete but increased by several orders of magnitude at pH 12 (for Al and Pb). Weathering and carbonation during long-term stockpiling, therefore, has a positive impact by producing a waste with stable pH and low metal leaching potential suitable for in-situ disposal as a void fill material

Enhanced Crystallographic incorporation of Strontium(II) ions to Calcite via Preferential Adsorption at Obtuse growth steps

Sr-containing calcium carbonates were precipitated from solutions containing Ca(OH)₂, SrCl₂ and Na₂CO₃ in a reactor where constant solution composition was maintained. The total concentration of divalent ions was same in all experiments, but the Sr/Ca ratio was varied between 0.002 and 0.86, and the pH value was between 12.02 and 12.25. All solutions were oversaturated with respect to calcite (SIcalcite = 1.2-1.5). Calcite was the only product formed at low Sr/Ca ratios, but at Sr/Ca ≥ 0.45 strontianite was detected in some systems. Sr-rich precipitate was observed in both a surface layer on (6.9-6 µm) rhombic calcite seed crystals and as smaller (> 3.64-1.96 µm) calcite crystals that were elongated along their C-axis. The degree of crystal elongation increased with the Sr/Ca ratio in those crystals. Precipitates recovered from low Sr/Ca ratio experiments exhibited an XRD spectrum identical to that of rhombic calcite, however the peaks attributed to Sr-containing calcite shifted progressively to lower 2θ values with increasing solution Sr/Ca ratio, indicating increased lattice volume. Sr K-edge EXAFS analysis of the precipitates showed that the shift in morphology and lattice volume is accompanied by a change in the local coordination of Sr²⁺ in calcite. The Sr-O bond lengths were similar to the Ca-O bond lengths in calcite, but Sr-O coordination increased from 6 fold in crystals containing 0.21 Wt. % Sr, to 8 fold in crystals containing 9.47 Wt. % Sr, and the Sr-Ca coordination decreased from 6 and 6 (for the first and second Sr-Ca shells respectively) to 4 and 1. It is suggested that Sr²⁺ undergoes preferential incorporation at obtuse (+) growth sites on the calcite surface due to its large ionic radius (1.13 Å), and this increases the growth rate parallel to the C-axis, resulting in the observed elongation in this direction

Nitroglycerin for treatment of retained placenta: a randomized, placebo-controlled, multicentre double blind trial in the UK

Funding: The GOT-IT trial was funded by the UK National Institute for Health Research (NIHR; https://www.nihr.ac.uk) Health Technology Assessment (HTA) Program in response to a specific commissioned grant call (Project number 12/29/01). The following co-authors were grant holders: FCD, GM, MP, JB, GS, JL, JN and JEN. The funders played no role in the study design, data collection, analysis, decision to publish or preparation of the manuscript. This work was undertaken in the MRC Centre for Reproductive Health which is funded by MRC Centre grant (MRC G1002033). Data Availability: The GOT-IT Trial contains a centrally-managed cross centre dataset which is available, upon request, from the Digital Curation Centre within the University of Edinburgh. Data requests can be made at [email protected] reviewedPublisher PD

Hera: evidence for multiple mineralization events and remobilization in a sediment-hosted Au-Pb-Zn-Ag deposit, Central New South Wales, Australia

The Hera Au-Ag-Pb-Zn deposit of central New South Wales, Australia with a total undepleted resource of 3.6 Mt @ 3.3 g/t Au, 25 g/t Ag, 2.6% Pb and 3.8% Zn occurs on the SE margin of the Cobar Basin. It is hosted by the shallow marine Mouramba Group and overlying turbiditic Amphitheatre Group. The siltstones comprise various mixtures of quartz, plagioclase, muscovite-phengite, biotite and clinochlore, along with accessory titanite and ilmenite. The deposit comprises a number of discrete lodes which are steeply west-dipping and strike NNW. Each lode has different abundances of the main ore minerals sphalerite, galena, chalcopyrite, pyrrhotite and electrum-gold. The North Pod and Far West lenses have the most diverse mineralogy in additionally containing arsenopyrite, native silver, gudmundite, Ag-tetrahedrite, acanthite, dyscrasite, native antimony, nisbite and breithauptite. Electrum (continuous spectrum from Ag-rich to Au-rich) is associated with sulfides in the main ore lenses while native gold occurs in the host rocks along cleavages/lineations and away from the main ore. The sulfur isotope data from across the deposit indicates a magmatic source. Most of the deposit has experienced greenschist facies metamorphism with pervasive green chlorite alteration, though the North Pod differs in being distinctly Ag- and Sb-rich and has reached at least amphibolite facies metamorphism with a garnet-wollastonite-vesuvianite-tremolite assemblage. Tremolite is relatively abundant throughout most of the deposit suggesting widespread low-T skarn alteration. Cross-cutting pegmatites comprise quartz, plagioclase (labradorite-andesine) and microcline. Hydrothermal remobilization is relatively extensive and best explains the unusual Ag-Sb-As assemblages of the North Pod and Far West lodes

Gravitational leptogenesis, C, CP and strong equivalence

The origin of matter-antimatter asymmetry is one of the most important outstanding problems at the interface of particle physics and cosmology. Gravitational leptogenesis (baryogenesis) provides a possible mechanism through explicit couplings of spacetime curvature to appropriate lepton (or baryon) currents. In this paper, the idea that these strong equivalence principle violating interactions could be generated automatically through quantum loop effects in curved spacetime is explored, focusing on the realisation of the discrete symmetries C, CP and CPT which must be broken to induce matter-antimatter asymmetry. The related issue of quantum corrections to the dispersion relation for neutrino propagation in curved spacetime is considered within a fully covariant framework.Comment: 32 pages, 5 figure