12 research outputs found

    Cambrian reworking of the southern Australian Proterozoic Curnamona Province: constraints from regional shear-zone systems

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    <p>Palaeoproterozoic to early Mesoproterozoic metamorphic rocks of the Curnamona Province, southern Australia, are crosscut by a system of regional-scale shear zones that locally dominate the terrain. Combined metamorphic and geochronological data from localities across the southern Curnamona Province indicate that the peak metamorphic shear-zone assemblages formed during the Cambrian (<em>c</em>. 500 Ma) Delamerian Orogeny, and not during the waning stages of the <em>c</em>. 1600 Ma Olarian Orogeny as has been previously asserted. A combination of monazite chemical U–Th–Pb and garnet Sm–Nd geochronology indicates that shear-zone fabrics formed between 497 and 517 Ma. Peak metamorphic conditions obtained from prograde garnet–staurolite–biotite–muscovite–chlorite–quartz assemblages are between 530 and 600 °C at pressures of around 5 kbar. The apparent absence of significant up-pressure prograde paths recorded by the mineral assemblages, together with modest (10–20%) Delamerian shortening, suggests that attainment of burial to depths of around 18 km was largely a function of pre-Delamerian sedimentation over the interval from <em>c</em>. 700 to 530 Ma. The spatial association between the pattern of basement metamorphism and reactivation during the Delamerian Orogeny is interpreted to reflect in part the distribution of pre-Delamerian sedimentation, and highlights the potential importance of pre-orogenic processes such as basin development in controlling the style and pattern of later terrain reactivation and reworking. </p

    Detrital zircon provenance constraints on the evolution of the Harts Range Metamorphic Complex (central Australia): links to the Centralian Superbasin

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    <p>Until recently it has been widely accepted that protoliths to metasediments of the Harts Range Metamorphic Complex (central Australia) were deposited prior to <em>c</em>. 1.75 Ga and form part of the Palaeoproterozoic Arunta Inlier. However, new sensitive high-resolution ion microprobe U–Pb analyses of detrital zircon, together with recently published data, suggest that they were deposited coeval with <em>c</em>. 545–520 Ma sediments from the adjacent, little metamorphosed Neoproterozoic to Palaeozoic Centralian Superbasin. Protoliths of the Harts Range Metamorphic Complex were deposited in the Irindina sub-basin, an early- to mid-Cambrian rift located between the present-day Amadeus and Georgina Basin remnants of the Centralian Superbasin. Deposition occurred during a widespread and long-lived interval of extension in parts of central Australia associated with eruption of the voluminous Kalkarinji Continental Flood Basalts. The Harts Range Metamorphic Complex was metamorphosed to upper amphibolite- to granulite-facies conditions within <em>c</em>. 40 Ma of deposition of its sedimentary protoliths. </p

    File 10: Robust laser ablation Lu–Hf dating of apatite: an empirical evaluation

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    Full Concordia plots for the zircon U–Pb data from the Reynolds–Anmatjira samples. The age calculation is based on the youngest concordant grains (green symbols) only. MSWD, mean squared weighted deviation; P(χ2), Chi-squared probability for a single data population

    File 3: Robust laser ablation Lu–Hf dating of apatite: an empirical evaluation

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    Isochron and weighted mean plots for the Lu–Hf matrix-correction standard (OD-306) and secondary standards HR-1 and Bamble-1. MSWD, mean squared weighted deviation; n, number of analyses; P(χ2), Chi-squared probability for a single data population. Where required (i.e. insufficient spread along the isochron), the isochrons were anchored to an initial 177Hf/176Hf ratio of 3.55 ± 0.05 (see text)

    File 1: Robust laser ablation Lu–Hf dating of apatite: an empirical evaluation

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    Concordia and weighted mean U–Pb plots for the secondary zircon, apatite, monazite and titanite standards. MSWD, mean squared weighted deviation; n, number of analyses

    File 5: Robust laser ablation Lu–Hf dating of apatite: an empirical evaluation

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    Apatite, monazite and titanite U–Pb and trace element data for all analysed samples (tab names refer to the four study areas), including data for the analytical standards. Rho, error correlation. All trace element data are reported in ppm concentrations. Log(LREE), logarithm of the sum of the La, Ce, Pr and Nd concentrations, which was used to distinguish age populations (see text)

    File 2: Robust laser ablation Lu–Hf dating of apatite: an empirical evaluation

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    Analytical conditions for the Lu–Hf and Ti-in-quartz laser sessions (named after the four study areas for this paper). *Laser spot diameters for standards are given within brackets

    File 9: Robust laser ablation Lu–Hf dating of apatite: an empirical evaluation

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    Thin section microphotographs from the Taratap Granodiorite. (A) Apatite cogenetic with allanite. (B) Apatite overgrown by monazite. (C, D) Titanite in chlorite ((C) transmitted light image; (D) reflective light image; circle symbols are laser ablation spots)
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