Rare earth element behaviour in apatite from the olympic dam Cu–U–Au–Ag deposit, South Australia

Apatite is a common magmatic accessory in the intrusive rocks hosting the giant ~1590 Ma Olympic Dam (OD) iron-oxide copper gold (IOCG) ore system, South Australia. Moreover, hydrothermal apatite is a locally abundant mineral throughout the altered and mineralized rocks within and enclosing the deposit. Based on compositional data for zoned apatite, we evaluate whether changes in the morphology and the rare earth element and Y (REY) chemistry of apatite can be used to constrain the fluid evolution from early to late hydrothermal stages at OD. The ~1.6 Ga Roxby Downs granite (RDG), host to the OD deposit, contains apatite as a magmatic accessory, locally in the high concentrations associated with mafic enclaves. Magmatic apatite commonly contains REY-poor cores and REY-enriched margins. The cores display a light rare earth element (LREE)-enriched chondrite-normalized fractionation pattern with a strong negative Eu anomaly. In contrast, later hydrothermal apatite, confined to samples where magmatic apatite has been obliterated due to advanced hematite-sericite alteration, displays a conspicuous, convex, middle rare earth element (MREE)-enriched pattern with a weak negative Eu anomaly. Such grains contain abundant inclusions of florencite and sericite. Within high-grade bornite ores from the deposit, apatite displays an extremely highly MREE-enriched chondrite-normalized fractionation trend with a positive Eu anomaly. Concentrations of U and Th in apatite mimic the behaviour of ∑REY and are richest in magmatic apatite hosted by RDG and the hydrothermal rims surrounding them. The shift from characteristic LREE-enriched magmatic and early hydrothermal apatite to later hydrothermal apatite displaying marked MREE-enriched trends (with lower U, Th, Pb and ∑REY concentrations) reflects the magmatic to hydrothermal transition. Additionally, the strong positive Eu anomaly in the MREE-enriched trends of apatite in high-grade bornite ores are attributable to alkaline fluid conditions.Sasha Krneta, Cristiana L. Ciobanu, Nigel J. Cook, Kathy Ehrig and Alkis Kontonikas-Charo

Identification of Ventricular Tachycardia Using Intracavitary Ventricular Electrograms: Analysis of Time and Frequency Domain Patterns

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74961/1/j.1540-8159.1988.tb06279.x.pd

Zircon at the nanoscale records metasomatic processes leading to large magmatic-hydrothermal ore systems

The petrography and geochemistry of zircon offers an exciting opportunity to better understand the genesis of, as well as identify pathfinders for, large magmatic–hydrothermal ore systems. Electron probe microanalysis, laser ablation inductively coupled plasma mass spectrometry, high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) imaging, and energy-dispersive X-ray spectrometry STEM mapping/spot analysis were combined to characterize Proterozoic granitic zircon in the eastern Gawler Craton, South Australia. Granites from the ~1.85 Ga Donington Suite and ~1.6 Ga Hiltaba Suite were selected from locations that are either mineralized or not, with the same style of iron-oxide copper gold (IOCG) mineralization. Although Donington Suite granites are host to mineralization in several prospects, only Hiltaba Suite granites are considered “fertile” in that their emplacement at ~1.6 Ga is associated with generation of one of the best metal-endowed IOCG provinces on Earth. Crystal oscillatory zoning with respect to non-formula elements, notably Fe and Cl, are textural and chemical features preserved in zircon, with no evidence for U or Pb accumulation relating to amorphization effects. Bands with Fe and Ca show mottling with respect to chloro–hydroxy–zircon nanoprecipitates. Lattice defects occur along fractures crosscutting such nanoprecipitates indicating fluid infiltration post-mottling. Lattice stretching and screw dislocations leading to expansion of the zircon structure are the only nanoscale structures attributable to self-induced irradiation damage. These features increase in abundance in zircons from granites hosting IOCG mineralization, including from the world-class Olympic Dam Cu–U–Au–Ag deposit. The nano- to micron-scale features documented reflect interaction between magmatic zircon and corrosive Fe–Cl-bearing fluids in an initial metasomatic event that follows magmatic crystallization and immediately precedes deposition of IOCG mineralization. Quantification of α-decay damage that could relate zircon alteration to the first percolation point in zircon gives ~100 Ma, a time interval that cannot be reconciled with the 2–4 Ma period between magmatic crystallization and onset of hydrothermal fluid flow. Crystal oscillatory zoning and nanoprecipitate mottling in zircon intensify with proximity to mineralization and represent a potential pathfinder to locate fertile granites associated with Cu–Au mineralization.Liam Courtney-Davies, Cristiana L. Ciobanu, Max R. Verdugo-Ihl, Ashley Slattery, Nigel J. Cook, Marija Dmitrijeva, William Keyser, Benjamin P. Wade, Urs I. Domnick, Kathy Ehrig, Jing Xu, and Alkiviadis Kontonikas-Charo

Behavior of Platinum-Group Elements during Hydrous Metamorphism: Constraints from Awaruite (Ni3Fe) Mineralization

Natural Fe-Ni alloys are common in meteorites and, presumably, the Earth’s core, where they host significant platinum-group elements (PGE). However, little is known on PGE concentrations in hydrothermal or metamorphic Fe-Ni alloys (i.e., awaruite Ni3Fe) from terrestrial rocks. In this work, we examine the geochemistry of awaruite and related minerals from several placer deposits sourced from the suprasubduction ophiolitic (Kamchatsky Mys, Karaginsky Island, and Mamet) and Ural-Alaskan (Galmoenan) complexes of Kamchatka and the Koryak Highlands (Far East Russia) in order to assess the abundance of PGE in awaruite and constrain their mobility under metamorphic and hydrothermal conditions. Studied awaruite from ophiolitic and Ural-Alaskan type complexes formed via desulfurization of pentlandite during serpentinization. Three groups of platinum-group minerals (PGMs) are associated with awaruite from Kamchatsky Mys: (1) Pt-Fe alloys such as ferronickelplatinum (Pt2FeNi) or unnamed Ni2FePt alloys; (2) Os-Ir-Ru alloys of various composition; (3) Pd-Sb minerals which form together with serpentine during hydrothermal alteration. Despite the abundance of PGM inclusions, no significant PGE concentrations were measured in awaruite from the Kamchatsky Mys, Karaginsky Island, or Mamet ophiolites. In contrast, pentlandite relicts in awaruite from placers related to the Galmoenan Ural-Alaskan type complex contain exceptionally high, previously unreported, Os (up to 540 ppm). Awaruite that forms on behalf of this pentlandite does not show any significant Os enrichment. Rare Galmoenan awaruite analyses yield up to 3 ppm Pd. The new data are not in complete accordance with previous studies that reported relatively high (up to first 10 ppm) PGE content in awaruite. We attribute this to low PGE concentration in precursor sulfides and preferential partitioning of PGE into discrete secondary PGM within awaruite. Nevertheless, abundant inclusions of secondary PGM in awaruite provide evidence of PGE mobility during metamorphic and hydrothermal alteration of ultramafic rocks

Metamorphic origin of large nuggets of platinum-group metals: evidence from multiphase inclusions in Os-Ir-Ru alloys from the Adamsfield placer, Tasmania

Platinum-group elements (PGE) are most effectively concentrated via sulfide-silicate melt immiscibility; however, under sulfide-undersaturated conditions, PGE may exhibit highly siderophile behavior and occur as native metals and alloys. In this case, they can form micrometer-size inclusions within Cr-spinel, but also large nuggets (up to several kilograms), found in chromitites and related placer deposits. The exact formation mechanism of such large nuggets and accumulations of PGE unrelated to sulfide melts remains controversial due to mass balance issues. In this study of multiphase inclusions in Os-Ir-Ru nuggets from the Adamsfield placer district (Tasmania, Australia), we constrain their crystallization environment. Multiphase inclusions comprise variable proportions of hornblende, enstatite, quartz, anthophyllite, anorthite, chlorite and native iridium and coexist with single-phase olivine and Cr-spinel inclusions. The heterogeneity in phase and chemical composition of the inclusions indicates a complex origin from an inhomogeneous source media. This is corroborated by grain scale disequilibrium mineral assemblages, where forsterite and quartz are both included within a single osmium grain. Our proposed multi-stage origin of Adamsfield Os-Ir-Ru nuggets involved magmatic olivine-Cr-spinel-Os-Ir-Ru cumulates in peridotite bodies that were subsequently overprinted by various hydrothermal and metamorphic processes, including serpentinization or growth of Os-Ir-Ru from supercritical fluids. The final metamorphic stage resulted in the obliteration of Os-Ir-Ru zonation, culminating in the current assemblage of inclusions

Onset of collectivity in neutron deficient Po196,198

We have studied via in-beam -ray spectroscopy Po196 and Po198, which are the first neutron-deficient Po isotopes to exhibit a collective low-lying structure. The ratios of yrast state energies and the E2 branching ratios of transitions from non-yrast to yrast states are indicative of a low-lying vibrational structure. The onset of collective motion in these isotopes can be attributed to the opening of the neutron i13/2 orbital at N112 and the resulting large overlap between the two valence protons in the h9/2 orbital and the valence neutrons in the i13/2 orbital

Insights into mammalian transcription control by systematic analysis of ChIP sequencing data

Abstract Background Transcription regulation is a major controller of gene expression dynamics during development and disease, where transcription factors (TFs) modulate expression of genes through direct or indirect DNA interaction. ChIP sequencing has become the most widely used technique to get a genome wide view of TF occupancy in a cell type of interest, mainly due to established standard protocols and a rapid decrease in the cost of sequencing. The number of available ChIP sequencing data sets in public domain is therefore ever increasing, including data generated by individual labs together with consortia such as the ENCODE project. Results A total of 1735 ChIP-sequencing datasets in mouse and human cell types and tissues were used to perform bioinformatic analyses to unravel diverse features of transcription control. 1- We used the Heat*seq webtool to investigate global relations across the ChIP-seq samples. 2- We demonstrated that factors have a specific genomic location preferences that are, for most factors, conserved across species. 3- Promoter proximal binding of factors was more conserved across cell types while the distal binding sites are more cell type specific. 4- We identified combinations of factors preferentially acting together in a cellular context. 5- Finally, by integrating the data with disease-associated gene loci from GWAS studies, we highlight the value of this data to associate novel regulators to disease. Conclusion In summary, we demonstrate how ChIP sequencing data integration and analysis is powerful to get new insights into mammalian transcription control and demonstrate the utility of various bioinformatic tools to generate novel testable hypothesis using this public resource

A user's guide to the Encyclopedia of DNA elements (ENCODE)

The mission of the Encyclopedia of DNA Elements (ENCODE) Project is to enable the scientific and medical communities to interpret the human genome sequence and apply it to understand human biology and improve health. The ENCODE Consortium is integrating multiple technologies and approaches in a collective effort to discover and define the functional elements encoded in the human genome, including genes, transcripts, and transcriptional regulatory regions, together with their attendant chromatin states and DNA methylation patterns. In the process, standards to ensure high-quality data have been implemented, and novel algorithms have been developed to facilitate analysis. Data and derived results are made available through a freely accessible database. Here we provide an overview of the project and the resources it is generating and illustrate the application of ENCODE data to interpret the human genome

Albitization and REE-U-enrichment in IOCG systems: insights from Moonta-Wallaroo, Yorke Peninsula, South Australia

This item is only available electronically.Iron Oxide Copper Gold (IOCG) deposits are the products of crustal-scale metasomatic alteration, generally considered to be associated with the emplacement of large felsic intrusions. These systems are typified by zoned, broad alteration haloes comprising the products of an early, barren albitization event, and late, ore-hosting potassic/calcic (skarn) alteration associated with mineralization. Yttrium and rare earth elements (REY), and also uranium, are prominent components of most IOCG systems. The REY-signatures of feldspars and accessory apatite, Fe-(Ti)-oxides and other minerals are geochemical tracers of alteration stages within a magmatic-hydrothermal system. This study sets out to identify links between magmatism and initiation of hydrothermal activity, and to test the hypothesis that albitization is a pre-requisite stage for REE-U enrichment in magmatically-derived IOCG systems. The compositions and trace element concentrations in key minerals have been analysed using scanning electron microscopy, electron probe microanalysis and laser-ablation inductively-coupled plasma mass spectrometry in a varied range of magmatic to metasedimentary lithologies from the Moonta-Wallaroo region, an area in which broad regional-scale alkali alteration is recognised. Results confirm a strong link between albitization and REE-U-enrichment. The process of albitization is seen to consume, redistribute and lock-in REY, LILE and HFSE via complex fluid-rock reactions dependent on the pre-existing mineral assemblages and fluid characteristics, providing a holistic model for IOCG-driven alkali metasomatism. The trace element signatures recorded by K-feldspar reflect a transition from magmatic to hydrothermal stages within an evolving IOCG system. Although further constraints on these signatures are required, they could prove invaluable in mineral exploration as they suggest a quantifiable distinction between alteration associated with mineralization, and regional background. This hypothesis requires testing elsewhere in the Olympic Province and in analogous terranes.Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 201