Matrix-matched iron-oxide laser ablation ICP-MS U–Pb geochronology using mixed solution standards

U–Pb dating of the common iron-oxide hematite (α-Fe2O3), using laser-ablation inductively-coupled-plasma mass-spectrometry (LA-ICP-MS), provides unparalleled insight into the timing and processes of mineral deposit formation. Until now, the full potential of this method has been negatively impacted by the lack of suitable matrix-matched standards. To achieve matrix-matching, we report an approach in which a U–Pb solution and ablated material from 99.99% synthetic hematite are simultaneously mixed in a nebulizer chamber and introduced to the ICP-MS. The standard solution contains fixed U- and Pb-isotope ratios, calibrated independently, and aspiration of the isotopically homogeneous solution negates the need for a matrix-matched, isotopically homogenous natural iron-oxide standard. An additional advantage of using the solution is that the individual U–Pb concentrations and isotope ratios can be adjusted to approximate that in the unknown, making the method efficient for dating hematite containing low (~10 ppm) to high (>1 wt %) U concentrations. The above-mentioned advantage to this solution method results in reliable datasets, with arguably-better accuracy in measuring U–Pb ratios than using GJ-1 Zircon as the primary standard, which cannot be employed for such low U concentrations. Statistical overlaps between 207Pb/206Pb weighted average ages (using GJ-1 Zircon) and U–Pb upper intercept ages (using the U–Pb mixed solution method) of two samples from iron-oxide copper-gold (IOCG) deposits in South Australia demonstrate that, although fractionation associated with a non-matrix matched standard does occur when using GJ-1 Zircon as the primary standard, it does not impact the 207Pb/206Pb or upper intercept age. Thus, GJ-1 Zircon can be considered reliable for dating hematite using LA-ICP-MS. Downhole fractionation of 206Pb/238U is observed to occur in spot analyses of hematite. The use of rasters in future studies will hopefully minimize this problem, allowing for matrix-matched data. Using the mixed-solution method in this study, we have validated a published hematite Pb–Pb age for Olympic Dam, and provide a new age (1604 ± 11 Ma) for a second deposit in the same province. These ages are further evidence that the IOCG mineralizing event is tied to large igneous province (LIP) magmatism in the region at ~1.6 Ga

Testing the potential of mycobacteriophage endolysins fused to biodegradable nanobeads for controlling mycobacteria : a thesis presented in partial fulfilment of the requirements for the degree of Master of Natural Sciences at Massey University, Albany, New Zealand

Figures 1, 2, 3B, 4 & 5A were removed for copyright reasons but may be accessed via their sources listed in the References.10.4 million people are diagnosed with tuberculosis, worldwide, every year, according to the World Health Organisation. Mycobacterium tuberculosis is a Gram-positive bacterial pathogen that can easily be transmitted to health care professionals and people supplying aid in these nations. Fortunately, over the last 100 years, the bacteriophage has gained traction as a suitable therapeutic, antibiotic-alternative against bacterial pathogens, such as M. tuberculosis. Herein I describe my work utilising endolysins the lytic protein that bacteriophages usually employ to burst out of the cell, but instead using these proteins to lyse “from without”. In order to develop a proof-of-principle product, we used the expansive M. smegmatis bacteriophage collection and chose eight endolysin candidates for testing against M. smegmatis. These endolysins were bioinformatically analysed for active domains before being synthesised and inserted into an expression vector to produce fused biodegradable nanobeads made of polyhydroxyalkanoate. These nanobeads were tested for activity against M. smegmatis, a safe mycobacterium closely related to pathogenic tuberculosis. Four distinct tests were carried out to test the efficiency of these beads in causing cell death in different situations (45 minutes and 5 hours, across concentrations of 10mg/ml, 20mg/ml and 80mg/ml. Ultimately the nanobead fusions of endolysin Inca (lysin B) caused the most cell death at 80mg/ml after exposure to M. smegmatis for 5 hours in a standing culture, at 78.87% cell death ± 5.21. When the nanobeads were applied to filter paper to mimic application to a hospital mask as a proof-of-concept approach before spraying with a bacterial aerosol, we saw that endolysin nanobead Jaws (lysin B) caused the most cell death with 75.54% ± 3.15 at 80mg/ml. These results are promising and present a unique opportunity to take advantage of an existing natural mechanism to use as a prophylactic defense against pathogenic bacteria in hospital settings

Geochronology of Iron Oxides and Development of Matrix-Matched Reference Material for Routine U-Pb Dating

Iron oxides, hematite and magnetite, are common minerals throughout rocks and ores of all types and ages. The discovery of U-bearing hematite at Olympic Dam, the largest iron oxide copper-gold (IOCG) deposit in the Gawler Craton (South Australia) prompted development of this mineral as a new U-Pb geochronometer. Unlike accessory minerals routinely used to track hydrothermal mineralisation, iron oxides are dominant components of Precambrian IOCG systems and therefore geochronology of iron oxides is pivotal to understand deposit evolution. Iron oxide minerals are studied in terms of U-Pb systematics and reliability for dating Olympic Dam and surrounding IOCG prospects formed at ~1.6 Ga. The temporal window between crystallisation of magmatic zircon and hydrothermal Fe-oxides is investigated to define the onset and lifespan of mineralisation and assess magma fertility. A matrix-matched reference material for routine microbeam geochronology is synthesised and tested for U/Pb isotope homogeneity by ID-TIMS. The U-Pb systematics of hematite are complex, exhibiting U-Th-Pb concentration and ratio heterogeneity at the nano- to micron-scales. Nevertheless, using a multi-instrument approach, high- precision data is routinely obtained. Reconnaissance SEM imaging in BSE mode and LA-ICP-MS isotope mapping allows pinpointing of U/Pb-homogeneous, inclusion-free grain domains. Dating of such domains via LA-ICP-MS using both mixed-(U/Pb)-solution and zircon reference materials produced successful results and a steppingstone to investigate at higher resolution and precision. The first application of both SHRIMP and ID-TIMS to hematite dating confirmed the robust U-Pb system in natural hematite, yielding 207Pb/206Pb (ID-TIMS) precision of up to ~0.05%. Coupled with (CA-)ID-TIMS analysis of magmatic zircon, hematite sampled throughout the Olympic Dam deposit provides a well constrained magmatic-hydrothermal timeline of events. The granite intrusion hosting Olympic Dam was emplaced rapidly at 1593.28 ± 0.28 Ma. The orebody was formed during a major mineralising event following granite uplift and during cupola collapse over a period of ~2 Ma, whereby the earliest hydrothermal activity is recorded in the early, deep ‘outer shell’ of the deposit at 1591.27 ± 0.89 Ma. Findings discredit a shallow origin for the deposit based on irreconcilable differences between the depth of granite emplacement and timeframes of uplift and fluid exsolution. Recognition of U-bearing hematite with a comparable W-Mo-Sn-bearing signature and age as Olympic Dam hematite within other IOCG systems, Wirrda Well and Acropolis, links the fluid forming the wider Olympic Cu-Au Province to a common source and time period. LA-ICP-MS U-Pb dating of U-bearing, silician magnetite from Fe-rich lithologies in the outer shell at Olympic Dan yields an age of 1761 ± 19 Ma, distinct from any other ages found within the deposit. The age is likely linked to ca. 1750 Ma intrusive/extrusive magmatism reported across the Gawler Craton. This shows the presence of older ore protoliths within Olympic Dam and represents the first successful application of U-Pb dating to magnetite. Magmatic zircon studied down to the nanoscale from two granite suites in the Gawler Craton shows crystal zoning with respect to ‘non-formulae’ elements such as Fe, Ca, and Cl, and also chloro-hydroxy-zircon nanoprecipitates when associated with IOCG mineralisation. This is indicative of early Fe-Cl-metasomatism prior to metamictisation, a diagnostic tool for assessing ‘fertility’ of granitic magmas. In contrast, metamict zircon from high-grade bornite ores shows patchy amorphisation throughout domains with pervasive enrichment in U-, Y- and non-formula elements. Hydrated ferric oxide doped with U-Pb solutions was converted to Fe-oxide and assessed by SEM imaging, XRD and LA-ICP-MS indicating the presence of homogenous U-Pb domains in cm-sized chips of hematite. Micro-sampled domains were measured by ID-TIMS confirming U-Pb isotope homogeneity at high precision. Hematite is a remarkably robust U-Pb geochronometer for dating hydrothermal ore deposits. Dissemination of the synthesized reference material to the wider community will allow routine LA-ICP-MS dating.Thesis (Ph.D.) -- University of Adelaide, School of Chemical Engineering & Advanced Materials, 202

Protecting the protected : reducing wildlife roadkill in protected areas

Social media discussions highlight public concern for wildlife‐vehicle collisions (WVCs) inside protected areas. Using a quasi‐experimental field trial, we investigated factors affecting the likelihood of WVCs within Pilanesberg National Park, South Africa, and assessed the comparative effectiveness of wildlife‐warning signage (WWS) for altering driver behaviour. We laid a dummy snake crosswise on roads across four combinations of habitat and road shape and recorded 10 driver‐related variables for 1454 vehicles that passed the dummy snake, including whether there was a collision. An interaction between speeding and driver occupation (staff/visitor) was the best indicator for WVC. When driving below the speed limit, visitors were almost three times more likely than staff to hit the dummy snake. Collision probabilities increased when speeding and became more similar between visitors and staff, although still significantly higher for visitors. We then investigated the effectiveness of roadside signage in modifying driver behaviour by erecting four variations of WWS, depicting a snake or a cheetah, and in photographic or silhouette form. We positioned the dummy snake 100 m or 1 km after the signage and recorded our 10 variables (n = 6400 vehicles). Sixty‐one per cent of drivers who passed a WWS changed their behaviour when they saw the dummy snake, compared to 37% with no sign present. Further, this behaviour change significantly reduced collisions, where 98% of drivers who changed their behaviour avoided a collision. Finally, an interaction between the animal depicted and distance before the dummy snake affected collisions. A WWS depicting a snake, and placed 100 m before the dummy snake, was most effective at reducing collisions. Our results suggest that drivers adapt their behaviour to signage that portrays smaller animals and awareness retention is low. Ultimately, to reduce WVCs within protected areas, we suggest steeper penalties for speeding and WWS placed in WVC hotpot areas.Table S1. The 45 candidate models used to investigate factors affecting wildlife collisions. The top model is indicated in bold, where delta AICc ≤ 2.Data S1. Supplementary material.https://zslpublications.onlinelibrary.wiley.com/journal/146917952020-08-01hj2019Mammal Research Institut

Heterotrophy mitigates the response of the temperate coral

Anthropogenic increases in atmospheric carbon dioxide concentration have caused global average sea surface temperature (SST) to increase by approximately 0.11°C per decade between 1971 and 2010 - a trend that is projected to continue through the 21st century. A multitude of research studies have demonstrated that increased SSTs compromise the coral holobiont (cnidarian host and its symbiotic algae) by reducing both host calcification and symbiont density, among other variables. However, we still do not fully understand the role of heterotrophy in the response of the coral holobiont to elevated temperature, particularly for temperate corals. Here, we conducted a pair of independent experiments to investigate the influence of heterotrophy on the response of the temperate scleractinian coral Oculina arbuscula to thermal stress. Colonies of O. arbuscula from Radio Island, North Carolina, were exposed to four feeding treatments (zero, low, moderate, and high concentrations of newly hatched Artemia sp. nauplii) across two independent temperature experiments (average annual SST (20°C) and average summer temperature (28°C) for the interval 2005-2012) to quantify the effects of heterotrophy on coral skeletal growth and symbiont density. Results suggest that heterotrophy mitigated both reduced skeletal growth and decreased symbiont density observed for unfed corals reared at 28°C. This study highlights the importance of heterotrophy in maintaining coral holobiont fitness under thermal stress and has important implications for the interpretation of coral response to climate change

Silician Magnetite: Si–Fe-nanoprecipitates and other mineral inclusions in magnetite from the Olympic Dam deposit, South Australia

A comprehensive nanoscale study on magnetite from samples from the outer, weakly mineralized shell at Olympic Dam, South Australia, has been undertaken using atom-scale resolution High Angle Annular Dark Field Scanning Transmission Electron Microscopy (HAADF STEM) imaging and STEM energy-dispersive X-ray spectrometry mapping and spot analysis, supported by STEM simulations. Silician magnetite within these samples is characterized and the significance of nanoscale inclusions in hydrothermal and magmatic magnetite addressed. Silician magnetite, here containing Si–Fe-nanoprecipitates and a diverse range of nanomineral inclusions [(ferro)actinolite, diopside and epidote but also U-, W-(Mo), Y-As- and As-S-nanoparticles] appears typical for these samples. We observe both silician magnetite nanoprecipitates with spinel-type structures and a γ-Fe₁.₅SiO₄ phase with maghemite structure. These are distinct from one another and occur as bleb-like and nm-wide strips along d₁₁₁ in magnetite, respectively. Overprinting of silician magnetite during transition from K-feldspar to sericite is also expressed as abundant lattice-scale defects (twinning, faults) associated with the transformation of nanoprecipitates with spinel structure into maghemite via Fe-vacancy ordering. Such mineral associations are characteristic of early, alkali-calcic alteration in the iron-oxide copper gold (IOCG) system at Olympic Dam. Magmatic magnetite from granite hosting the deposit is quite distinct from silician magnetite and features nanomineral associations of hercynite-ulvöspinel-ilmenite. Silician magnetite has petrogenetic value in defining stages of ore deposit evolution at Olympic Dam and for IOCG systems elsewhere. The new data also add new perspectives into the definition of silician magnetite and its occurrence in ore deposits.Cristiana L. Ciobanu, Max R. Verdugo-Ihl, Ashley Slattery, Nigel J. Cook, Kathy Ehrig, Liam Courtney-Davies, and Benjamin P. Wad