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Granulites from the Narryer Terrane in the northern Yilgarn Craton, Australia, record evidence for high to ultrahigh thermal gradients during the Meso–Neoarchean. U–Pb zircon ages reflect a complex history of high‐grade, prolonged and poly‐phase metamorphism, with evidence for several thermal pulses at ca. 2745–2725, ca. 2690–2660, and ca. 2650–2610 Ma. Forward phase equilibrium modeling on rocks with varying bulk compositions and mineral assemblages suggests that peak temperatures reached 880–920°C at pressures of 5.5–6 kbar at ca. 2690–2665 Ma, followed by near‐isobaric cooling. These new P–T results also indicate that these rocks experienced some of the hottest thermal gradient regimes in the metamorphic record (≥150°C/kbar). Based on P–T models, U–Pb ages, and geochemical constraints, our data suggest that the geodynamic setting for the formation of this unusual thermal regime is ultimately tied to cratonization of the Yilgarn Craton. Previous models have inferred that ultrahigh thermal gradients and coeval large‐scale anatexis in the Narryer Terrane were primarily generated by mantle‐driven processes, despite most of the lithological, isotopic, and geochemical observations being at odds with the expected geological expression of large‐scale mantle upwelling. We re‐evaluate the mechanisms for high‐grade metamorphism in the Narryer terrane and propose that long‐lived high crustal temperatures between ca. 2690 Ma and 2610 Ma were instead facilitated by elevated radiogenic heat production in thickened, highly differentiated ancient crust. Mantle‐derived magma input and new crustal addition may not be the only drivers for high‐ to ultrahigh‐temperature metamorphism and stabilization of ancient crustal blocks. [ABSTRACT FROM AUTHOR]

This study is the first to constrain the absolute timing of hypogene iron mineralization in Archean BIF located in the Yilgarn Craton. In situ SHRIMP U–Th–Pb geochronology on xenotime and monazite grains has been used to constrain the age of hypogene magnetite replacement ores at the Beebyn deposit and hypogene magnetite vein ores at the Madoonga deposit in the Weld Range study area. The Beebyn magnetite replacement ores (c. 2627 Ma) are younger than the published maximum depositional age of the BIF hosts of the Wilgie Mia Formation (2792 ± 9 Ma) and partially overlaps crystallization ages of granitic rocks (2757–2606 Ma) that intrude supracrustal rocks throughout the study area. These plutons, and their probable subvolcanic expressions, are considered to be likely sources of energy and fluids responsible for magnetite replacement ores. In contrast, Madoonga magnetite veins record multiple dates: the first at 2857 ± 41 Ma, followed by events at c. 2775 Ma through 1812 Ma. The two oldest monazite dates of 2857 ± 41 and 2832 ± 51 Ma are interpreted to be mineralization ages for magnetite veins, possibly related to subseafloor volcanism and base metal VMS systems; whereas the younger dates (i.e. 2775–1812 Ma) probably represent multiple episodes of phosphate mineral precipitation related to reactivation of structures and overprinting by discrete pulses of hydrothermal fluids. The Madoonga BIFs are genetically distinct from the Beebyn BIFs and are the oldest dated BIFs at Weld Range, being older than c. 2857 Ma, but younger than the c. 2970 Ma felsic volcanic rocks in the stratigraphic footwall to the Madoonga BIFs. Hydrothermal events at the Madoonga deposit (2215–2120 Ma) coincide with published dates for rifting, mafic–ultramafic magmatism, and basin development along the northern margin of the Yilgarn Craton (2215–2145 Ma), whereas the younger phosphate mineral dates correspond with the Glenburgh (2002–1947 Ma) and Capricorn Orogenies (1817–1772 Ma). Tectonic activity along the northern margin of the Yilgarn Craton coincides with reported ages for hematite mineralization in BIF-hosted iron-ore deposits in the Hamersley Basin and Pilbara Craton, suggesting the far-reaching effects of tectonism along paleocratonic boundaries as drivers for iron mineralization in BIF. [ABSTRACT FROM AUTHOR]

The Golden Mile deposit (1767 t Au) in the Archean Yilgarn Craton, Western Australia, is controlled by D2 strike-slip and D3 reverse faults displacing folded tholeiitic greenstones. Granodiorite and monzodiorite dykes emplaced into the faults predate and are synchronous with propylitic and sericite–ankerite alteration overprinted by the ore. Arsenopyrite and chlorite thermometry and fluid-inclusion data indicate ore formation at 420 ± 30 °C and 300 MPa and cooling to the ambient temperature at 10 km depth (250–300 °C). Fimiston refractory ore (7 g/t Au) in propylitic Golden Mile Dolerite is zoned from inner albite–ankerite to outer ankerite–phengite–quartz replacement. Pyrite–magnetite is overprinted by pyrite–hematite ± anhydrite. Arsenical pyrite encloses chalcopyrite, tennantite, gold and tellurides. Gold thio-sulfide complexes, buffered by magmatic SO2 and H2S in the fluid, were destabilised during the ankerite–pyrite replacement of propylitic chlorite, a reaction releasing hydrogen ions for the hydrolitic alteration of adjacent albite. Gold deposition was assisted by declining gold, silver, tellurium and sulfur solubility as the fluid cooled. Dissolved sulfate is recorded in pyrite by negative δ34S (− 10 to − 5‰) at magmatic Δ33S (0–0.2‰). Oroya ore bodies are subdivided into oxidised pyrite lodes (5 g/t Au) in propylitic GMD and reduced lodes (30–120 g/t Au) characterised by Stage 1 silica–pyrite and siderite–chlorite replacement in ankerite-rich wall rocks. Rapid cooling, an acidic fluid and the retrograde solubility of ankerite facilitated replacement and the deposition of minor arsenopyrite, pyrrhotite, chalcopyrite, sphalerite and gold. Locally, the H2S-rich fluid (log fS2 = − 5.8 ± 0.5 bar at 420 °C) was reduced by organic methane. Oroya Stage 2 ore fills crosscutting veins and cements breccia. Quartz, chalcedony, dolomite–ankerite, calcite, V-muscovite, V-chlorite and V-tourmaline form the gangue of pyrite–telluride ± magnetite ore. Altaite–tellurium myrmekites were deposited at ≥ 400 °C as melt droplets together with tellurantimony, altaite, calaverite, montbrayite and petzite. As fluid temperature and tellurium fugacity declined, free gold, krennerite, coloradoite and melonite also crystallised joined by sylvanite and hessite below 350 °C. Finally, trace covellite and digenite precipitated at high fluid sulfidation states. [ABSTRACT FROM AUTHOR]

The shells of two marine bivalve species (Fulvia tenuicostata and Soletellina biradiata), endemic to south Western Australia, have been characterised using a combined crystallographic, spectroscopic and geochemical approach. Both species have been described previously as purely aragonitic, however, this study identified the presence of three phases, namely aragonite, calcite and Mg-calcite using XRD analysis. Data obtained via confocal Raman spectroscopy, electron probe microanalysis, and laser ablation inductively coupled plasma-mass spectrometry (LA ICP-MS) show correlations between Mg/S and Mg/P in F. tenuicostata, and Sr/S and S/Ba in S. biradiata. The composition of organic macromolecules that constitute the shell organic matrix (i.e. soluble phosphorus-dominated and/or insoluble sulphur-dominated fraction) influences the incorporation of Mg, Sr and Ba into the crystal lattice. Ionic substitution, particularly Ca2+ by Mg2+ in calcite in F. tenuicostata, appears to have been promoted by the combination of both S- and P-dominated organic macromolecules. The elemental composition of these two marine bivalve shells is species-specific and is influenced by many factors such as crystallographic structure, organic macromolecule composition and environmental setting. In order to reliably use bivalve shells as proxies for paleoenvironmental reconstructions, both the organic and inorganic crystalline material need to be characterised to account for all influencing factors and accurately describe the "vital effect". [ABSTRACT FROM AUTHOR]

Background: Benzodiazepines (BZDs) are used to treat sleep disturbances and behavioural and psychological symptoms of dementia in residents of aged-care facilities. Older people are vulnerable to the adverse effects of BZDs. In Australia, guidelines exist for prescribing BZDs, however there are a lack of data comparing prescribing patterns with guidelines. Aim: To review BZD prescribing patterns in residential aged-care facilities and to compare these with best-practice guidelines. Method: A cross-sectional analysis of BZD prescribing for residents aged 65 years and over was undertaken in 6 aged-care facilities. Data on patient demographics and BZD prescribing were obtained from medication charts, medical records and case notes. BZD prescribing patterns were compared to guidelines from the National Prescribing Service and Therapeutic Guidelines. Results: Prescribing data for 193 residents were analysed. 71 (37%) residents were prescribed a BZD, mostly temazepam and oxazepam. The majority of prescriptions complied with the guidelines with respect to dose, but all exceeded the recommended duration of therapy. 55 (77%) residents had comorbidities for which guidelines recommended avoiding BZDs, such as a history of falls. Conclusion: Although the choice and dose of BZD were appropriate, prescribing did not adhere to guidelines because of the extended duration of therapy. Residents with comorbidities where BZDs should be avoided were frequently prescribed a BZD. [ABSTRACT FROM AUTHOR]

Aim: To describe the prescribing patterns of dexamethasone in a cohort of palliative care inpatients. Method: Data were collected from a consecutive sample of patients admitted to 2 palliative care units over an 8 week period. Data on dexamethasone use was also collected, i.e. indication for use, dosages, concurrent medications, adverse effects, blood glucose levels and reasons for changes in dose. Results: 359 patients were admitted during the recruitment period and 185 (52%) were prescribed dexamethasone. 37 (20%) patients were prescribed dexamethasone for specific indications, such as cerebral disease, spinal cord compression and bowel obstruction. The majority of dexamethasone was prescribed for non-specific indications: poor appetite, nausea, and poor wellbeing. A range of doses was prescribed for eachindication and during their inpatient stay most patients (65%) had their dose reduced. Adverse effects were commonly reported; 117 (63%) patients experienced adverse effects attributable to dexamethasone.Conclusion: Dexamethasone use is widespread in palliative care for a myriad of indications. [ABSTRACT FROM AUTHOR]

The increasing application of minor elements such as REE, Ti, Fe in zircon as petrogenetic indicators depends on zircon remaining a closed chemical system over a history that can include metamorphic events, erosion, transport, and sedimentation. Whereas examples have been described of U Pb loss and element exchange during metamorphic reactions, for over 50 years there have been reports of the accumulation of a range of non-formula elements such as Ca, Al, Fe, in zircons with no metamorphic history that have been tentatively related to hydrothermal action or some other process such as weathering. This open system behaviour of zircons needs further explanation and in this contribution we present data from three zircons from a late Archaean granite from Western Australia that confirm previous observations on the distribution of non-formula elements in radiation damaged zircon and support our earlier conclusion that elements are added from percolating low temperature weathering solutions and provide new insights into the mechanisms and processes controlling access of weathering fluids into the zircon. These include radiation damage accumulation over time from the decay of U and Th to produce domains of porous amorphous material that vary in porosity and the presence of weaknesses along the boundaries of oscillatory zones which allow the penetration of low temperature groundwater fluids carrying solute elements. Also important is the size of particles of the solute elements such as Al and Ca, which depends on Eh - pH of the groundwater and porous domains within the zircon structure. This low temperature fluid interaction is distinguished from hydrothermal activity by a lack of any reaction fronts or annealing of the radiation damage and a lack of any modification of existing zircon structures. Capillary action is proposed as the mechanism driving the penetration of weathering solutions into radiation damage expansion fractures and the radiation damaged zonal structure. The susceptibility of radiation damaged zircon to infusion by low temperature fluids and deposition of accompanying solute elements has implications for the application of zircon trace element chemistry as a petrogenetic and temperature indicator as well as a geochronometer and host for nuclear waste. [ABSTRACT FROM AUTHOR]

Cassiterite, rutile and gahnite from Scuddles VMS primary ore have accumulated residually in silcrete and in ferruginous lateritic zones (duricrust and gravel) that cap the weathering profile at Scuddles. Cassiterite and rutile contain inclusions of base metal sulfides and sulfosalts which are stable under alkaline and reducing conditions in the supergene sulfide enrichment zone, and alkaline to neutral conditions in the supergene oxide enrichment zone. However, cassiterite and rutile have been intensively corroded in the silcrete and lateritic zones under oxidizing conditions by acidic fluids derived by infiltration of acidic meteoric water and the oxidation of sulfide inclusions. This has resulted in releasing a suite of pathfinder elements, including Sn, Cu, Zn, Cd, Hg, Pb, Sb, Bi, W, Mo, Se and Te. The released Cu, Zn and Cd tend to be mobile under these conditions and are leached from the silcrete and lateritic zones. However, these elements are elevated at certain stratigraphic zones in silcrete and form surface anomalies in exposed saprolite. The other, less mobile elements, particularly Pb, Sb, Bi, W and Mo are concentrated in silcrete and ferruginous duricrust to form a variety of secondary microcrystalline phases of mixed or of unestablished mineralogy, including QRAZ (quartz, rutile, anatase, and zircon) and more complex Pb-, Ag-, Bi- and Sb-bearing phases. These pathfinder elements form a narrow, near-surface anomaly that delineates the Scuddles VMS deposit. This paper also reinforces findings that silcrete, ferruginous duricrust and ferruginous gravel are anomalous in pathfinder elements over the Scuddles deposit and, furthermore, are important sampling media in mineral exploration in general, particularly where gossans may not have formed or have been eroded. • Geochemical anomaly in weathering profile above the VMS formed by accumulation of resistant minerals • Gahnite, cassiterite and rutile in leached and lateritic zones contain sulfide inclusions. • Weathering of cassiterite and rutile released pathfinder elements such as Pb, Bi and Sb. • Multi-element anomalies in leached and lateritic zones delineate the Scuddles VMS deposit. [ABSTRACT FROM AUTHOR]