Gerd Rantitsch

Metamorphic evolution of the Tethyan Himalayan flysch in SE Tibet

Abstract The metamorphic conditions and the age of thermal overprint were determined in metapelites, metaarenites and metabasites of the Tethyan Himalayan Sequence (THS) in SE Tibet using Kübler Index and vitrinite reflectance data and applying thermobarometrical (Thermocalc and PERPLEX) and geochronological methods (illite/muscovite K–Ar and zircon and apatite (U–Th)/He chronology). The multiple folded thrust pile experienced a thermal overprint reaching locally peak conditions between the diagenetic stage (c. 170 °C) and the amphibolite facies (c. 600 °C at 10 kbar). Burial diagenesis and heating due to Early Cretaceous dyke emplacement triggered the growth of illite in the metapelites. Eocene collision-related peak metamorphic conditions have been reached at c. 44 Ma. During collision the different tectonic blocks of the THS were tectonically buried to different structural levels so that they experienced maximum greenschist to amphibolite facies metamorphism. Later, during Oligocene to Miocene times the entire THS underwent anchi- to epizonal metamorphic conditions, probably associated to continuous deformation in the flysch fold-thrust-system. This period terminated at c. 24–22 Ma. Adjacent to the north Himalayan metamorphic domes, the base of the THS was metamorphosed during Miocene times (c. 13 Ma). Post-metamorphic cooling below c. 180 °C lasted until Late Miocene and took place at different times.

Thermal history of the Carnic Alps (Southern Alps, Austria) and its palaeogeographic implications

Abstract The thermal history of the Carnic Alps (Southern Alps, Austria) has been investigated by means of organic petrology, clay mineralogy and microthermometry. In the tectonic framework of the Carnic Alps the metamorphic overprint from the lower anchizone up to the epizone is exposed in a continuous NS-trending metamorphic section. The metamorphic zonation is disturbed by shear zones related to the strike-slip movement of the Periadriatic Lineament. All obtained data, a methodical correlation and a numeric 1D simulation of the burial history result in the model of a multistage thermal history: (1) a Variscan tectonothermal event caused a syntectonic anchi- to epizonal metamorphism with the development of local overpressured zones, characterized by convective heat transfer; (2) major strike-slip faults operating during the sedimentation of the Late Carboniferous molasse are related to enhance the heat flow; (3) the Alpine metamorphic overprint shows the same intensity as the Variscan event; (4) high-temperature fluid inclusion phases are related to Oligocene plutonic activity along the Periadriatic Lineament. These data from the Carnic Alps are discussed in a general framework of the non- to low-grade metamorphic units of the internal Alps and Carpathians. In the uppermost tectonic units of the Eastern and Southern Alps, a spatial and temporal shift of the Alpine very low-grade metamorphic overprint from north to south is observed. This zonation indicates the Pannonian Transdanubian Range (which suffered no Alpine metamorphism) as an exotic block inside an Alpine heated domain. The Gailtal Line, as a segment of the Periadriatic Lineament, separates two terrains with the same Alpine overprint.

Coalification and graphitization of graptolites in the anchizone and lower epizone

Abstract In Lower Paleozoic sediments of the South Alpine Carnic Alps (Carinthia, Austria) fragments of graptolites were used to trace the process of coalification and graphitization in a continuous anchizonal to epizonal metamorphic section. Beginning with the onset of meta-anthracitic coal ranks, the process of graphitization produces graptolites with the structure of ‘coke-like transitional matter’. The path of coalification of graptolite fragments is explained by the model of a reflectance indicating surface (RIS). This path resembles the coalification of vitrinite. During the process of coalification the shape of the RIS shows a non-coaxial evolution, starting with a primary biaxial negative geometry. The oblate graptolite RIS shapes of the Carnic Alps are indicative of a metamorphic event with only minor tectonic influence.

Characterization of organic matter in late Cretaceous black shales of the Eastern Alps (Kainach Gosau Group, Austria)

Abstract Bituminous marls occur at the base of the late Cretaceous Kainach Gosau Basin, Eastern Alps. They interfinger with local coaly layers, and are overlain by a turbiditic sequence. Forty outcrop samples with different lithologies were studied by Rock-Eval pyrolysis. Seven bituminous marls, one coaly sample, two siltstones from the turbiditic sequence and solid bitumen from the Paleozoic basement have been characterized in detail by organic geochemical and petrographic techniques. The organic matter from bituminous marls can be subdivided into allochthonous, terrigenous material (mainly recycled vitrinite), which is present in all samples in similar amounts, and autochthonous hydrogen-rich organic matter (alginite, liptodetrinite), which is most probably of lacustrine origin. Organic richness varies from 0.4 to 2.3% TOC. The amount of the autochthonous organic matter is controlled primarily by different oxygen concentrations. Sedimentological (lack of bioturbation) and geochemical data (e.g., pristane/phytane ratios, homohopane indices, C∗ 30 C 29 Ts ratios, distribution of phenol and alkylphenols in the pyrolyzate) suggest that the water column above the sediment surface was suboxic to dysoxic, but probably not anoxic. High energy events were responsible for short periods with enriched oxygen in the water column. The organic matter in the resulting sediments is of a residual type. Drift wood was transported from the nearby shore into the lake. Paleontological evidence proves a temporary marine influence. Vitrinite reflectance and Tmax indicate maturation levels ranging from the beginning to the peak stage of oil generation. Despite the fact that some hydrocarbons have already been generated, HI values of kerogens of bituminous marls reach 605 mg HC/g TOC. Most analysed bituminous marls produce a high wax paraffinic oil during maturation and are good sources for oil. Pyrolysis-gas chromatography and biomarker data indicate that changing wax contents of oils generated from bituminous marls might be a function of different oxygen concentrations in the water column. Coaly samples have a very good gas potential.

Hydrocarbon-bearing fluid inclusions in the Drau Range (Eastern Alps, Austria): implications for the genesis of Bleiberg-type Pb-Zn deposits

SummaryHydrocarbons in ore minerals of Bleiberg-type Pb-Zn deposits and in authigenic quartz of the Drau Range (Eastern Alps) have been analysed by bulk-sample gas chromatography and fluorescence microscopy. Microthermometric data and the molecular composition of the hydrocarbons indicate a hot (120° to 130°C) pulse of migrating condensate-like hydrocarbons within Late Triassic sediments during Middle Cretaceous to Early Tertiary times. The molecular composition of hydrocarbons enclosed in authigenic quartz corresponds to the composition of hydrocarbons trapped in Bleiberg-type ore minerals, therefore a common fluid source is assumed. The hydrocarbons possibly played an important role as reducing agents in the late stage of sulfide precipitation.ZusammenfassungDie organo-chemische Zusammensetzung von Kohlenwasserstoffen, die in Erzmineralen vom Typus Bleiberg and in authigenen Quarzen des Drauzuges (Ostalpen) eingeschlossen sind, wurde durch gaschromatographische and fluoreszenzmikroskopische Untersuchungen charakterisiert. Mikrothermometrische Daten und die molekulare Zusammensetzung dieser Kohlenwasserstoffphasen weisen auf migrierende kondensatartige Kohlenwasserstoffe in den Sedimenten der Obertrias während des Zeitraumes zwischen der Mittelkreide und dem Alttertiär hin. In Erzmineralen der Pb-Zn-Vererzungen vom Bleiberg-Typ können Kohlenwasserstoffe nachgewiesen werden deren molekulare Zusammensetzung dem Chemismus von Kohlenwasserstoffen, die in authigenen Quarzen eingeschlossen wurden, entspricht. Es wird vermutet, daß diese Kohlenwasserstoffe während der späten Vererzungsphase als Reduktanten wirkten.

Alpine metamorphism in the central segment of the Western Greywacke Zone (Eastern Alps)

Alpine metamorphism in the central segment of the Western Greywacke Zone (Eastern Alps) The metamorphic pattern of the central Western Greywacke Zone (Austroalpine, Eastern Alps) was investigated by organic matter reflectance, Raman spectroscopy on organic matter and clay mineralogical methods. Raman data map a 10 km wide thermal aureole along the contact zone of the Greywacke Zone to the Penninic Tauern Window. The estimated maximum temperatures of 400 °C to 200 °C decrease from South to North, that is from the contact to the uppermost parts of the Greywacke Zone. This pattern is explained by an Oligocene to Miocene thermal pulse, related to the rapid exhumation of formerly deeply buried rocks of the Penninic unit. During this event, advective heat transport and circulating fluids overprinted the Cretaceous higher anchi- to lower epizonal metamorphic pattern of the central Western Greywacke Zone.

Lehrstuhl für Geologie und Lagerstättenlehre

ZusammenfassungDie Forschungsfelder liegen umfassend im Bereich der mineralischen Rohstoffe und ihrer Lagerstätten. Die Lehre konzentriert sich in den Bakkalaureat- und Magisterprogrammen der Studienrichtungen Angewandte Geowissenschaften, Natural Resources und Petroleum Engineering auf die Grundlagen der Geologie, Lagerstättenkunde und Montangeologie.AbstractResearch is focused on various aspects of mineral resources and their deposits. The courses offered for the bachelor and magister programmes in Applied Geosciences, Natural Resources and Petroleum Engineering cover a broad field of geological basics, deposit prospecting and mining geology.