Oligocene emplacement of the Eclogite Zone of the central Tauern Window, Eastern Alps, Austria

The EZ is an approximately 20km long and 2–3km wide coherent unit of the Tauern Window in the Eastern Alps. It is sandwiched between the Venedigerand the Glockner Nappe. While rocks in the EZ experienced HP metamorphic conditions (24 kbar/650°C), rocks from the underlying Venediger Nappe and the overlying Glockner Nappe only record lower alpine metamorphic conditions with peak pressures not exceeding 10 and 8 kbar, respectively. While metamorphism in the EZ is well dated with an average age of 31.5±0.7Ma (Glodny et al. 2005) the final emplacement of these different nappes is still under debate. Our Rb-Sr-data indicate that top-N thrusting at the base and large-scale folding of the EZ was coeval with sinistral strike-slip faulting at its upper boundary and eclogite-facies metamorphism in the EZ. The data also indicate that today’s nappe architecture must have been established in less than 2Ma after the eclogite facies metamorphism in the EZ. Very fast exhumation of the EZ was accomplished in a transpressional setting, which might explain why the exposed EZ is such a small unit.conferenc

Storytelling für und mit türkischstämmigen pflegenden Angehörigen

Glodny S. Storytelling für und mit türkischstämmigen pflegenden Angehörigen. Bielefeld: Universität Bielefeld; 2018

Rb-Sr and in situ 40Ar/39Ar dating of exhumation-related shearing and fluid-induced recrystallization in the Sesia zone (Western Alps, Italy)

The Sesia zone in the Italian Western Alps is a piece of continental crust that has been subducted to eclogite-facies conditions and records a complex metamorphic history. The exact timing of events and the significance of geochronological information are debated due to the interplay of tectonic, metamorphic, and metasomatic processes. Here we present new geochronological data using Rb-Sr internal mineral isochrons and in situ Ar-40/Ar-39 laser ablation data to provide constraints on the relative importance of fluid-mediated mineral replacement reactions and diffusion for the interpretation of radiogenic isotope signatures, and on the use of these isotopic systems for dating metamorphic and variably deformed rocks. Our study focuses on the shear zone at the contact between two major lithological units of the Sesia zone, the eclogitic micaschists and the gneiss minuti. Metasedimentary rocks of the eclogitic micaschists unit contain phengite with step-like zoning in major element chemistry as evidence for petrologic disequilibrium. Distinct Ar-40/Ar-39 spot ages of relict phengite cores and over-printed rims demonstrate the preservation of individual age domains in the crystals. The eclogitic micaschists also show systematic Sr isotope disequilibria among different phengite populations, so that minimum ages of relict assemblage crystallization can be differentiated from the timing of late increments of deformation. The preservation of these disequilibrium features shows the lack of diffusive re-equilibration and underpins that fluid-assisted dissolution and recrystallization reactions are the main factors controlling the isotope record in these subduction-related metamorphic rocks. Blueschist-facies mylonites record deformation along the major shear zone that separates the eclogitic micaschists from the gneiss minuti. Two Rb-Sr isochrones that comprise several white mica fractions and glaucophane constrain the timing of this deformation and accompanying near-complete blueschist-facies re-equilibration of the Rb-Sr system to 60.1 +/- 0.9 Ma and 60.9 +/- 2.1 Ma, respectively. Overlapping ages in eclogitic micaschists of 60.1 +/- 1.1 (Rb-Sr isochron of sheared matrix assemblage), 58.6 +/- 0.8, and 60.9 +/- 0.4 Ma (white mica Ar-40/Ar-39 inverse isochron ages) support the significance of this age and show that fluid-rock interaction and partial re-equilibration occurred as much as several kilometers away from the shear zone. An earlier equilibration during high-pressure conditions in the eclogitic mica schists is recorded in minimum Rb-Sr ages for relict assemblages (77.2 +/- 0.8 and 72.4 +/- 1.1 Ma) and an Ar-40/Ar-39 inverse isochron age of 75.4 +/- 0.8 Ma for white mica cores, again demonstrating that the two isotope systems provide mutually supporting geochronological information. Local reactivation and recrystallization along the shear zone lasted >15 m.y., as late increments of deformation are recorded in a greenschist-facies mylonite by a Rb-Sr isochron age of 46.5 +/- 0.7 Ma

Petrochronology of polygenetic white micas (Naxos, Greece)

Naxos in the Greek Cyclades preserves a type example of polymetamorphism. The southern and northern parts of the island record different Tertiary P–T histories between Eocene and Miocene times, including a blueschist facies event, one or more amphibolite/greenschist facies overprint(s) and contact metamorphism. Age attributions for these events are inconsistent in the literature. Here, we propose a new approach that combines electron probe microanalyzer (EPMA) characterization of the white mica (WM) with $^{39}$Ar-$^{40}$Ar–Rb-Sr multichronometry. Textural–petrographic–compositional observations reveal that the polygenetic WM consists of five different generations: pre-Eocene relicts, paragonite, high-Si phengite, low-Si phengite and muscovite. EPMA mapping of four WM samples, previously analysed by Rb-Sr, reveals major element compositions heterogeneous down to the μm scale. Each WM consists of chemically distinct generations, documenting submicron-scale retrogression of high-pressure (HP) phengite grains to muscovite. Four WM samples from a N-S traverse across the island were analysed by $^{39}$Ar-$^{40}$Ar stepheating, comparing coarse and fine sieve size fractions to obtain overdetermined K-Ar systematics. Fine sieve fractions are richer in Cl than coarse ones. Linear arrays in Cl/K-age isotope correlation diagrams show two predominant WM generations (one Cl-poor at ca. 38 Ma and one Cl-rich at <20 Ma). A lower-grade sample from southern Naxos was less pervasively recrystallized, provides older ages and preserves at least three WM generations, including a relict WM with a pre-Palaeocene K-Ar age, consistent with the high Ar retentivity of WM in the absence of complete recrystallization. The age of the Cl-poor end-member WM approximates the age of the HP event, 38 Ma. Ar inheritance in Cretaceous mica relicts is heterogeneous at the single-grain scale. Comparing the degassing rates of the WM fractions rules out ‘multidomain’ diffusion. As no sample is monomineralic, the degassing rate of each polygenetic mica is instead controlled by the mass balanced sum of the unrelated rate constants of its constituent minerals. Given the commonness of zoned and composite micas, the approach detailed here is potentially useful for reconstructing polyphase metamorphic histories worldwide

Subclavian artery rupture in a young man during excessive weight lifting

We report a 19-year-old man with rupture of the right subclavian artery after an excessive exercise of weight lifting. Imaging showed a hematothorax and hematomediastinum, a pseudoaneurysm with a maximum diameter of 4 cm, and a dissection of the right vertebral artery. As an emergency procedure an interposition graft was performed for reconstruction of the right subclavian artery. The patient's postoperative course was uneventful, and he was symptom free except for regressive hoarseness due to a paresis of the right recurrent laryngeal nerve

Syn-metamorphic folding in the Tauern Window, Austria dated by Th-Pb ages from individual allanite porphyroblasts

High-precision 232Th-208Pb dates have been obtained from allanite porphyroblasts that show unambiguous microstructural relationships to fabrics in a major syn-metamorphic fold in the SE Tauern Window, Austria. Three porphyroblasts were analysed from a single garnet mica schist from the Peripheral Schieferhülle in the core of the Ankogel Synform, one of a series of folds which developed shortly before the thermal peak of Alpine epidote-amphibolite facies metamorphism: allanite grain 1 provided two analyses with a combined age of 27.7 ± 0.7 Ma; grain 2, which was slightly bent and fractured during crenulation, provided two analyses with a combined age of 27.7 ± 0.4 Ma; a single analysis from grain 3, which overgrew an already crenulated fabric, gave an age of 28.0 ± 1.4 Ma. The five 232Th-208Pb ages agree within error and define an isochron with an age of 27.71 ± 0.36 Ma (95% confidence level; MSWD = 0.46). The results imply that the crenulation event was in progress in a short interval (<1 Ma) c. 28 Ma, and that the Ankogel Synform was forming at this time. The thermal peak of regional metamorphism in the SE Tauern Window was probably attained shortly after 28 Ma, only c. 5 Ma after eclogite facies metamorphism in the central Tauern Window. Metasediment may contain allanite porphyroblasts with clear-cut microstructural relationships to fabric development and metamorphic crystallization; for such rocks, 232Th-208Pb dating on microsamples offers a powerful geochronological tool

Vascular anomaly in bilateral ectopic kidney: a case report

Ectopic kidney occurs as a result of a halt in migration of kidneys to their normal locations during embryonal period. While kidneys ascend through pelvis, they receive new branches from vessels (iliac and aorta) close to them. When they reach the highest point, they receive new branches from aorta and the former branches degenerate. Renal vessels do not degenerate in the ectopic caudal kidney, more than one accessory and polar arteries may arise. In various studies, a possibility of association between presence of multiple renal arteries and hypertension, has been reported. We aimed to present a case with bilateral ectopic kidney and vascular anomaly associated with hypertension and renal dysfunction

Plume–lithosphere interactions and LIP-triggered climate crises constrained by the origin of Karoo lamproites

We identified a ca. 180 Ma diamondiferous lamproite event in Zambia, establishing a link between ultrapotassic volcanism and the early Jurassic Karoo flood basalt province of sub-Saharan Africa. The cratonic lamproites erupted through the Permo–Triassic Luangwa Rift structure, but MgO-rich ultrapotassic magma formation was unrelated to rifting and triggered by plume–lithosphere interactions during the Karoo LIP event. Elevated Li–Zn–Ti concentrations in magmatic olivine (up to 18.5 ppm Li at 86–90 mol.% forsterite) and strong Sr–Nd–Hf–Pb isotopic enrichment of the host lamproites ( 87Sr/86Sr = 0.70701–0.70855, εNd = − 10.8 to − 10, εHf = − 20.3 to − 19.1, 206Pb/204Pb = 16.8–17.5) suggest partial melting of phlogopite-metasomatized lithospheric mantle domains, at approximately 180–200 km depth. The mantle-like δ7 Li values (+2.8 to +5.7‰) of the most pristine lamproite samples are compatible with source enrichment by asthenosphere-derived melts, without significant involvement of recycled sedimentary components. This geochemical fingerprint stands in sharp contrast to the negative δ7 Li compositions of primitive K-rich volcanic rocks from collision zone settings, where the shallow mantle sources contain recycled sediment. Isotope modelling demonstrates that the sub-Saharan lamproites originate from a MARID-style metasomatized peridotitic mantle source that underwent incompatible element enrichment at ca. 1 Ga, during tectonic activity associated with Rodinia supercontinent formation. Plume-sourced basaltic and picritic magmas of the 180 Ma Karoo LIP interacted with such K-rich hydrous lithospheric mantle domains, thereby attaining enriched incompatible element and radiogenic isotope compositions. Nd–Hf isotope mass balance suggests that up to 25% of MARID-sourced lamproite melt component contributed to some of the high-Ti flood volcanic units. Although large quantities of volatiles can be transferred from Earth’s mantle to the atmosphere via plume–lithosphere interactions, it is unlikely that outgassing of mantle-sourced sulphur can exceed the climatic impact caused by the release of much more abundant carbon from thick continental roots. Thus, the excess SO2 required to account for transient atmospheric cooling during the early Jurassic, coincident with the Karoo LIP event, must have had a thermogenic origin near the surface of Earth