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We report composition and age data from a restricted <370 km2, volcano-sedimentary basin beneath Mesozoic cover to the northwest of the Flinders Ranges, South Australia. This volcano-sedimentary basin comprises two components: a sedimentary sequence that includes shales, siltstones and sandstones, and a basalt–sedimentary member. Together, these components are defined as the Ooloo Hill Formation. Whole-rock K–Ar geochronology for five basalt samples yields a preferred mean K–Ar age of 392 ± 8 Ma. Two samples of detrital zircons from the sedimentary rock yield SHRIMP U–Pb maximum depositional ages of ca 527 and 510 Ma. These ages are significant, as they rule out a Neoproterozoic age for the sedimentary basin and demonstrate that this basin is not part of the Adelaide Superbasin. Lower eruptive sequences are calc-alkaline and mafic in composition (SiO2 = 46.1–47.8 wt%, Na2O + K2O = 3.7–6.1 wt%, MgO = 6.85–8.37 wt%, Mg# = 57–65 and εNd(390 Ma) = 3.4–4.0) and may represent two small-scale melting events from compositionally distinct mantle reservoirs. The uppermost eruptive sequence is tholeiitic andesite (SiO2 = 51.6 wt%, Na2O + K2O = 8.1 wt%, MgO = 2.2 wt%, Mg# = 27 and εNd(390 Ma) = 3.0) and displays geochemical affinity to the first two eruptive sequences, possibly representing a differentiated magma from a similar source region. Incompatible trace-element ratios and isotopic compositions suggest the source was a heterogeneous oceanic island basalt-like parent magma derived from partial melting of the asthenospheric mantle. We envisage decompressional melting was linked to large-scale tectonic processes inboard of the Tasman Orogen, with magma ascent facilitated by crustal faulting. First record of a mid-Devonian intracontinental volcano-sedimentary basin in South Australia. Basalts have an oceanic island basalt-like mantle source that represents at least two small-scale melting events from compositionally distinct mantle reservoirs. A localised mid-Devonian backarc basin or transpressional/transtensional basin linked to intracontinental faulting formed inboard of the Tasman Orogen. [ABSTRACT FROM AUTHOR]

Reconstructing ancient tectonic environments is inherently difficult and requires the integration of many datasets. Here we attempt to reconstruct the tectonic setting of a Proterozoic magmatic rock suite from the Archean to Mesoproterozoic Gawler Craton, South Australia. We evaluate previous models of subduction or non-subduction tectonics for the St Peter Suite through field observations coupled with geochemical and isotopic data. Field observations indicate the presence of mafic magma chambers, felsic plutons and zones of mixing represented by multiphase plutons and zones of magma transfer. Syn-magmatic and solid-state deformation fabrics suggest magmatism was associated with a compressional tectonic regime, at least during some stages of magmatism. Zircon U–Pb geochronology suggests magmatism occurred between ca 1633 and ca 1608 Ma, an interval of ca 25 Myr. Mafic rocks are tholeiitic and enrichment in high field strength and light rare earth elements supports a modified mantle source region. Mafic rocks have εNd1620 Ma values around 0, and zircon εHf(t) values around 4, supporting minor crustal contamination. Felsic plutons have a geochemical signature similar to average continental crust, εNd1620 Ma between –3.7 and 0.4, and zircon Lu–Hf isotopic compositions that yield to εHf(t) values between –1.8 and 7.7, suggesting they were derived from fractionation of enriched tholeiitic parent magmas. A model for the formation of the St Peter Suite that is most consistent with the available data is one that places the magmatism in a broadly continental magmatic arc setting, albeit one in which little or no Archean crust was involved. Potentially this magmatic arc could have been built on a thinned, or hyper-extended continental margin. The integration of structural, geochemical and isotopic constraints has provided a more holistic view of the St Peter Suite petrogenesis than previously available. Evaluation of models of subduction vs non-subduction tectonics for formation of Paleoproterozoic magmatic suite Evidence for syn-magmatic compression and mafic–felsic magma mingling Isotopically juvenile (Nd--Sr--Hf) with mantle-like zircon δ18O values Continental arc setting proposed, possibly on hyper-extended continental margin [ABSTRACT FROM AUTHOR]

The Olympic Cu–Au Province, Gawler Craton, is host to the Olympic Dam and Prominent Hill iron oxide–copper–gold (IOCG) deposits. Both of these deposits and the region between the two are covered by Neoproterozoic to Cenozoic sediment, making inferences about prospectivity in this portion of the Olympic Domain reliant on geophysical interpretation and sparse drill hole information. We present new U–Pb zircon sensitive high resolution ion microprobe (SHRIMP) dates from two basement intersecting drill holes in the region between Olympic Dam and Prominent Hill that show bimodal volcanism occurred at 2555 ± 5 Ma, and was followed by intrusion of tonalite at 2529 ± 6 Ma. Laser40Ar/39Ar dating of biotite and muscovite from the tonalite yields ages aroundca2000 Ma, consistent with slow cooling trends observed in Archean rocks elsewhere in the northern Gawler Craton. Step heating experiments on K-feldspar from the same tonalite yields an age spectrum with older ages around 1740 Ma from the highest temperature steps becoming progressively younger to a minimum of 1565 Ma in the lowest temperature heating steps; this is consistent with either Paleoproterozic cooling to final closure of K-feldspar by 1565 Ma or a reheating event atca1565 Ma, with the latter more likely, given the evidence for sub-solidus alteration of the K-feldspar. Sericite within hematite–sericite–chlorite altered portions of the tonalite yield a poorly defined age ofca1.6 Ga. Taken together the40Ar/39Ar data providing evidence for a fluid event affecting this region between Olympic Dam and Prominent Hill during the early Mesoproterozoic. Low temperature quartz–carbonate–adularia veins occur in <10 cm wide fractures within basalt in one drill hole in this region. Adularia from these veins yields40Ar/39Ar ages that span fromca1.3–1.1 Ga. This age range is interpreted to approximate either the timing of adularia formation during a hydrothermal event or the timing of resetting of the40Ar/39Ar systematics within the adularia as a result of fluid flow in this sample. This is evidence for a mid-Mesoproterozoic fluid event in the Gawler Craton and necessitates a reconsideration of the long-term stability of the craton, as it appears to have been affected, at least locally, by fluid flow related to a much larger event within the Australian continent, the Musgrave Orogeny. [ABSTRACT FROM AUTHOR]

Development and use of on-farm assays to detect antimicrobial residues in milk is important to reduce the risk of violative residues in marketed milk. The objective of this study was to evaluate the effectiveness of a lateral-flow immunodiagnostic assay (BetaStar Plus, Neogen Corp., Lansing, MI) in detecting ceftiofur residues in milk from individual cows treated for mastitis. This assay is currently approved by the US Federal Drug Administration (FDA) for detecting β-lactam residues in commingled milk. Forty-five dairy cows with clinical mastitis from 4 dairy farms were enrolled and treated intramammary with 125 mg of ceftiofur hydrochloride (Spectramast LC, Zoetis, Madison, NJ) according to the manufacturer's label recommendation. Composite milk samples were collected (A) before first intramammary antimicrobial treatment, (B) before the last intramammary antimicrobial treatment, (C) the last milking of the product-labeled milk withhold, (D) the first milking after the product-labeled milk withhold had been met, and (E) 72 h after the product-labeled milk withhold had been met. Samples were tested using the BetaStar Plus assay within 48 h of collection. Parallel samples were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and for somatic cell count and milk components. The BetaStar Plus assay identified 6.7, 60.0, 46.7, 22.2, and 6.7% positive samples at each of the respective time points. The assay had sensitivity and specificity of 100 and 84.7%, respectively, compared with liquid chromatography-tandem mass spectrometry analysis using FDA published residue tolerance levels for ceftiofur (or ceftiofur metabolites) as a threshold. The BetaStar Plus assay could be useful for detecting ceftiofur residues in milk from individual cows following intramammary treatment for mastitis before the milk is shipped for processing. [ABSTRACT FROM AUTHOR]