Application of micro-computed X-ray tomography for improving the hole erosion test analysis on high plastic clay     

Zaid  Bahaeldeen  Vollert  Florian  Gibmeier  Jens  Mengel  Lena  Stelzer  Oliver  Schneider  Achim 《Acta Geotechnica》2023,18(2):865-876

Acta Geotechnica - The hole erosion test (HET) was developed to simulate piping erosion and to study the erosion parameters of cohesive soils. The erosion rate in the HET is evaluated by the...  相似文献   

Geochemistry and geochronology of HP mélanges from Tinos and Andros,cycladic blueschist belt,Greece     

Florian Bulle  Michael Bröcker  Claudia Gärtner  Alan Keasling 《Lithos》2010,117(1-4):61-81

U–Pb zircon geochronology, Sr–Nd isotope and bulk-rock geochemistry have been applied to meta-igneous and meta-sedimentary rocks from high-pressure metamorphic mélanges exposed on the Cycladic islands of Tinos, Syros and Andros. Ion microprobe (SHRIMP) U–Pb zircon dating of 7 samples representing meta-igneous blocks (Tinos), a blackwall zone (Tinos) and chlorite–talc schists from block-matrix contacts (Syros and Tinos) yielded Cretaceous ages of c. 80 Ma. Many of the criteria commonly used to distinguish between magmatic or metamorphic zircon genesis (internal structure, Th/U ratio, REE characteristics, Ti-in zircon thermometry, enclosed mineral phases) do not provide unambiguous constraints for the mode of formation. However, a magmatic origin for Cretaceous zircon of meta-gabbros and eclogites is considered likely. Supporting evidence for a previously suggested metamorphic origin for c. 80 Ma zircon in eclogite has not been found. Zircon of the same age occurring in chlorite–talc schists is presumably related to non-magmatic processes. Well-defined Cretaceous age groups clustering at c. 79 Ma also occur in the detrital zircon populations of 2 quartz mica schists representing the mélange matrix on Tinos, and suggest a much later time for sediment accumulation than previously assumed. The importance of c. 57 Ma zircon ages remains unclear, but may record either HP metamorphic processes or a post-57 Ma depositional age. The youngest age group in a third quartz mica schist from Tinos, collected outside the main mélange occurrences, clusters at c. 226–238 Ma. In all clastic metasediments from Tinos, most data points plot along the concordia between c. 300 and 900 Ma; single data points indicate concordant ages of c. 2.5 Ga, 2.3 Ga and 1 Ga, respectively. The youngest ²⁰⁶Pb/²³⁸U age group that has been recognized in a felsic paragneiss from Andros indicates an age of 163.1 ± 3.9 Ma, and mostly represents overgrowths around zircon with ages in the range from ～ 272 to ～ 289 Ma. Single data points of other inherited cores provided ²⁰⁶Pb/²³⁸U ages of c. 630 and c. 930 Ma. Meta-gabbros from Tinos show a large compositional variability and were found at 4 locations, each with distinct compositional characteristics, suggesting different crystallization histories, different sources and/or significant post-magmatic disturbance. The geochemistry of mélange blocks and the identical U–Pb zircon ages suggest that the block-matrix associations on Tinos and Syros can be grouped together. On a broader regional scale, there seem to be similarities between some meta-igneous rocks from Tinos and Evvia. Field relationships indicate that the mélanges occurring in southern Andros and northern Tinos can be correlated, but supporting geochemical and/or geochronological evidence for this interpretation could not be established. Previously published Jurassic ages for mafic and felsic mélange blocks from Andros suggest a genetic relationship to the ophiolite occurrences exposed in the larger Balkan region. A similar regional correlation is also considered likely for the Cretaceous meta-gabbros from Tinos and Syros, but cannot be documented with certainty.  相似文献   

Beitrag zur Kenntnis der Cordillera Claudio Gay (Nordchile)     

Dr. Florian Kubaner  Prof. Dr. Werner Zeil 《International Journal of Earth Sciences》1971,60(3):1009-1024

Zusammenfassung Die wenig bekannte Cordillera Claudio Gay ist ein Teil der Vorkordillere in Nordchile. Ihr Unterbau besteht aus Tiefengesteinskörpern des PalÄozoikums und einer Sedimentserie, die von sauren Ergu\gesteinen durchbrochen wird. Die petrologische Zusammensetzung der Sedimente und ihre metamorphe überprÄgung werden speziell behandelt. Da keine Fossilien vorliegen, kann das Alter der Sedimente nur auf eine Zeitspanne zwischen Devon und Perm eingeengt werden.

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The little-known Cordillera Claudio Gay is part of the Pre-Cordillera in Northern Chile. Its basement consists of plutonic rocks of the Paleozoics and of a sediment series which is penetrated by acid effusive rocks. The petrological composition of low grade metamorphosed sediments is separately dealt with. No fossils being available, the age of the sediments can only be defined as belonging to the period between Devonian and Permian time.

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Resumen La poco conocida Cordillera Claudio Gay es una parte de la Precordillera en Chile septentrional. Su base se compone de masas intrusivas paleozóicas y de una serie sedimentaria cortada por rocas efusivas ácidas. La composición petrológica de los sedimentos y su cambio metamórfico son investigados en forma especial. La edad de los sedimentos solo puede ser calculada por la falta de fósiles entre el Devónico y el Pérmico.

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Schallausbreitung im Schlick     

Dipl.-Phys. Florian Schirmer 《Ocean Dynamics》1970,23(1):24-30

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Calcium isotope fractionation in calcite and aragonite   总被引：1，自引：0，他引：1  

Nikolaus Gussone  Florian Böhm  Martin Dietzel  Barbara M.A. Teichert  Gert Wörheide 《Geochimica et cosmochimica acta》2005,69(18):4485-4494

Calcium isotope fractionation was measured on skeletal aragonite and calcite from different marine biota and on inorganic calcite. Precipitation temperatures ranged from 0 to 28°C. Calcium isotope fractionation shows a temperature dependence in accordance with previous observations: 1000 · ln(α_cc) = −1.4 + 0.021 · T (°C) for calcite and 1000 · ln(α_ar) = −1.9 + 0.017 · T (°C) for aragonite. Within uncertainty the temperature slopes are identical for the two polymorphs. However, at all temperatures calcium isotopes are more fractionated in aragonite than in calcite. The offset in δ^44/40Ca is about 0.6‰. The underlying mechanism for this offset may be related to the different coordination numbers and bond strengths of the calcium ions in calcite and aragonite crystals, or to different Ca reaction behavior at the solid-liquid interface. Recently, the observed temperature dependence of the Ca isotope fractionation was explained quantitatively by the temperature control on precipitation rates of calcium carbonates in an experimental setting (Lemarchand et al., 2004). We show that this mechanism can in principle also be applied to CaCO₃ precipitation in natural environments in normal marine settings. Following this model, Ca isotope fractionation in marine Ca carbonates is primarily controlled by precipitation rates. On the other hand the larger Ca isotope fractionation of aragonite compared to calcite can not be explained by different precipitation rates. The rate control model of Ca isotope fractionation predicts a strong dependence of the Ca isotopic composition of carbonates on ambient CO₃²⁻ concentration. While this model is in general accordance with our observations in marine carbonates, cultured specimens of the planktic foraminifer Orbulina universa show no dependence of Ca-isotope fractionation on the ambient CO₃²⁻ concentration. The latter observation implies that the carbonate chemistry in the calcifying vesicles of the foraminifer is independent from the ambient carbonate ion concentration of the surrounding water.  相似文献   

Wide-angle observations of ALP 2002 shots on the TRANSALP profile: Linking the two DSS projects     

Florian Bleibinhaus  Ewald Brückl  ALP Working Group 《Tectonophysics》2006,414(1-4):71

Dynamite shots of the crustal-scale refraction seismic project ALP 2002 were recorded by an array of 40 seismological three-component stations on the TRANSALP profile. These observations provide a direct link between the two deep seismic projects. We report preliminary results obtained from these data. In a first approach, we verified the TRANSALP refraction seismic velocity model computing travel times for several shots and comparing them to the new observations. The results generally confirm this model. Significant first-break travel time differences in and near the Tauern Window are explained by anisotropy. Large-scale features of the model, particularly the Moho structure, seem to be continuous towards the east. Travel time residuals of wide-angle reflections indicate a slight eastward dip component of the Adriatic Moho.  相似文献   

Whole-grain evaporation for 207Pb/206Pb-age-investigations on single zircons using a double-filament thermal ion source     

Bernd Kober 《Contributions to Mineralogy and Petrology》1986,93(4):482-490

A technique has been developed and tested to analyse ²⁰⁷Pb/²⁰⁶Pb apparent ages by thermal evaporation of radiogenic lead directly from untreated whole zircon grains (0.3 mm). The evaporation analyses are performed in the double-filament arrangement of a thermal ion mass spectrometer (ThIMS). The method is a powerful tool to distinguish between different lead components occurring in the same grain because differing activation energies of the competing lead components cause their sequential evaporation from the zircons. The evaporation of test samples results in ²⁰⁷Pb/²⁰⁶Pb apparent ages in good agreement with U/Pb ages known from literature: single zircons from a granite of the Marble Mountains/California yield an age of crystallization of 1,410±30 Ma; Ceylon zircons from heavy-mineral bearing gravels yield 560± 40 Ma as age of crystallization of the pegmatitic gravel sources; individuals from a heterogeneous zircon population of a diatexite from the Southern Schwarzwald/SW-Germany indicate metamorphic zircon formation around 500 Ma and the existence of Middle-Proterozoic relics (1.95±0.05 Ga).The evaporation analyses revealed closed-system U/Pb evolution of the crystalline domains of all investigated zircons irrespective of discordancy-trends documented by U/Pb analyses on related zircon concentrates. Therefore the majority of discordia-lines derived from U/Pb isotope distributions of zircon samples are supposed to be due to phase mixing. Lead components from the crystalline domains are concordant end members of the mixing arrays. Open-system behaviour and U/Pb fractionation should be attributed only to phases with low Pb activation energies eg. metamict zircon domains or intergrown non-zircon minerals.  相似文献   

Pre-Hercynian mantle lead transfer to basement rocks as indicated by lead isotopes of the Schwarzwald crystalline,SW-Germany     

Bernd Kober  Hans Joachim Lippolt 《Contributions to Mineralogy and Petrology》1985,90(2-3):162-171

Lead isotopes of K-feldspars from five granites of the SE-Schwarzwald and from metamorphites are positively correlated in 207/204 as well- as 208/204- vs. 206/204-diagrams. The linear alignments may be due to correlated laststage lead isotope evolution (lead-lead isochron) and result in a secondary isochron model age of nearly 3 Ga for the Southern Schwarzwald basement. This calculation implies a long-lasting undisturbed lead isotope evolution in the Schwarzwald basement since the Archaean. This is not supported however by geochronological studies. On the other hand the data together with U/Pb-analyses of whole rock samples from metamorphites are consistent with pre-Hercynian mantle lead addition to the basement. This presumably happened during early Paleozoic polymetamorphism. The interpretation of the lead isotope correlations as mantle-crust mixing lines needs a rather homogeneous pre-Hercynian mantle lead of the MORB-type, delivered to the crust probably in part by ascending volatile phases. Thus geodynamical models are supported which involve subduction of oceanic crust or mantle pluming during the early Paleozoic. In Part I of this report, the trends in Schwarzwald lead isotopes are discussed as secondary isochrons and as mixing lines. Constraints are derived for a pre-Hercynian mantlecrust interaction and for lead redistribution by the Hercynian basement activation.  相似文献   

Lateral variations in sediment composition and bedding in Middle Triassic interplatform basins (Buchenstein Formation, southern Alps, Italy)     

Florian Maurer  Wolfgang Schlager 《Sedimentology》2003,50(1):1-22

ABSTRACT Hemipelagic deposits are widespread in Triassic sequences of the Alpine belt and provide important data for stratigraphy and the study of bedding rhythms. The area of the western and central Dolomites of northern Italy escaped strong alpidic deformation and preserves such deposits in their original palaeogeographic setting. The Buchenstein Formation, the object of this study, was deposited in up to 1000 m deep, Middle Triassic interplatform basins, which extend over an area of 500 km² within the Dolomites. Excellent outcrops and volcaniclastic markers allow a detailed correlation of the formation in both laminated (anoxic) and bioturbated facies down to a bed scale, and show its relationship to coeval carbonate platforms. Correlation of lithostratigraphically well‐constrained intervals in the bioturbated facies reveal that lateral thickening and thinning of the deposits depends on the amount of shallow‐water debris in the succession and is a function of the distance to coeval carbonate platform sources. In the laminated background deposit, thickness variations in limestones and marls parallel the thickness variations in ash layers, and were caused by local redeposition of sediment on the basin floor. Lateral persistence of laminae indicates that bottom currents were weak in the Buchenstein basin, but were able to redeposit mud in a significant way. In the area around Seceda and Geisler (western Dolomites), a lateral transition from dark‐grey laminated to grey bioturbated to red bioturbated facies is observed, which is probably linked to local relief with different oxygenation conditions on the sea floor. A comparison shows that decimetre‐scale bedding is preserved in all facies types and that the bedding rhythm is partly the result of different cementation of the sediment during early diagenesis. Correlation of individual layers in the bioturbated facies reveals that beds are thicker and enriched in lime mud in the western part of the basin, and decrease in thickness and contain less micrite towards the east, further away from the main shallow‐water areas. Nearslope calciturbidites change gradually from distinct layers into lateral arrays of micrite nodules and bands further out in the basin. These observations point to a platform source of lime mud in the Buchenstein basin.  相似文献   

Calcium isotope fractionation in modern scleractinian corals     

Florian Böhm  Nikolaus Gussone  Anton Eisenhauer  Stéphanie Reynaud 《Geochimica et cosmochimica acta》2006,70(17):4452-4462

The ⁴⁴Ca/⁴⁰Ca ratios of cultured (Acropora sp.) and open ocean (Pavona clavus, Porites sp.) tropical reef corals are positively correlated with growth temperature. The slope of the temperature-fractionation relation is similar to inorganic aragonite precipitates. However, δ^44/40Ca of the coral aragonite is offset from inorganic and sclerosponge aragonite by about +0.5‰. This offset can neither be explained by the very fast, biologically controlled calcification of scleractinian corals, nor as a consequence of calcification from a partly closed volume of fluid. As corals actively transport calcium through several cell layers to the site of calcification, the most likely explanation for the offset is a biologically induced fractionation. Our results indicate a limited use of Ca isotopes in scleractinian corals as temperature proxy.  相似文献