Till Heinrichs

The formation of meso‐ and macroporous gas hydrates

We present results of experimental studies on the formation of gas hydrates (clathrates) at conditions of geophysical interest. Clathrate hydrates formed by a reaction of gas at ice Ih surfaces are always found to be mesoporous to macroporous with pores sizes between 100 to 400 nm and pore volumes of approximately 25–40% for CH4, Ar and N2 hydrate, and smaller pores of 20 to 100 nm with a porosity of approximately 10–20% for CO2 hydrate. The three-dimensional sponge-like microstructure occurs in single crystalline grains of typically a few µm size and was observed by field-emission scanning electron microscopy. It forms over a wide range of p-T conditions below the ice Ih melting. The porous microstructure is stable for at least several months, even close to the clathrate decomposition, and is proposed to be formed by local differences in the energy balance between hydrate formation and ice decompositon. The results presented are considered of potential major importance for the understanding of the behaviour of natural gas hydrates found e.g. in polar ice sheets and permafrost regions, and also in some celestial bodies.

The emplacement of the Rieserferner Pluton (Eastern Alps, Tyrol): constraints from field observations, magnetic fabrics and microstructures

Abstract Within the alpine chain several Tertiary intrusions (e.g. Bergell, Adamello) intruded along the Periadriatic Lineament. This study attempts to show how the Rieserferner Pluton (Vedrette di Ries) is related to the Defereggen-Antholz-Vals (DAV)-Line. For a survey of the fabric pattern over the pluton the anisotropy of the magnetic susceptibility (AMS) was determined on nearly 170 samples. Low bulk susceptibilities of K vol –6 SI and a total degree of anisotropy P′

Crustal-scale balanced cross sections through the Variscan fold belt, Germany: the central EGT-segment

Abstract This paper presents crustal-scale, geometrically and isostatically balanced cross sections through the Rhenohercynian and Saxothuringian zones of the Variscan fold belt of Germany. The cross sections are based on surface geological data and on results of the DEKORP deep reflection profiles. They were constructed by means of computer-assisted, iterative forward modelling. The Rhenohercynian zone, corresponding to the Externides of the Variscan belt, developed out of a some 300 km wide rifted continental margin sedimentary prism, limited to the south by the narrow Giessen oceanic basin. During Carboniferous imbrication this shelf sequence is stripped of its basement above one or more decollements and shortened by some 150 km. Closure of the Giessen ocean and emplacement of the ophiolite bearing Giessen nappe entailed a minimum additional 200 km of crustal shortening. The structure of the model correlates well with the present outcrop pattern of rock units, their metamorphic history, the seismic and magnetotelluric architecture of the crust, and its present regional distribution of thickness. The deeper crust beneath the Rhenish Massif is probably devoid of extremely weak decollement horizons and pronounced rheological stratification. In the southward adjacent Saxothuringian zone, nappe development involving the stacking of crustal slices during Middle Devonian to Visean times accounts for a further 170 km of crustal shortening above an infracrustal, partly blind thrust system with flat-ramp-geometry. Total crustal shortening in the analyzed profiles is estimated to be of the order of 520 km; this figure is a conservative value. Prominent uncertainties include the unknown importance of crustal wrenching, the state of strain within thrust units, the distribution of strain within the lower crust, and major changes in thrusting directions during the course of orogenic history.

Tumors of the respiratory tract observed at the German Primate Center, 1978–1994

Abstract: Eight spontaneous pulmonary tumors (four bronchiolar tubular adenomas, two bronchiolar adenocarcinomas, two squamous‐cell carcinomas) occurred in a total of 54 adult tree shrews (Tupaia belangeri) of the GPC colonies between 1978 and 1994. The adenomas and adenocarcinomas consisted of tubularly or trabecularly arranged cuboidal to cylindrical cells interspersed with some PAS‐positive goblet cells, thus resembling the epithelial lining of respiratory bronchioles of tree shrews. The two squamous‐cell carcinomas probably originated from the pulmonary alveoles.

The gravity field along the Central Segment of the EGT

Abstract We give an overview of the gravity field of central Europe based on a compilation of Bouguer maps available by mid-1989. A generalized gravity map corrected for Moho effects is presented as well as several filtered maps of the second derivative. Additionally, sediment-stripped Bouguer maps are used in the case of the Northwest German Basin and for northeastern Franconia. The North German Line, the Erzgebirge Minimum, the Kraichgau High and the Regensburg-Gottingen Low are treated in detail and a number of geologic interpretations are discussed.

The Waqf as Suwwan crater, Eastern Desert of Jordan: aspects of the deep structure of an oblique impact from reflection seismic and gravity data

The deeply eroded Waqf as Suwwan ring structure was recently discovered to be a large impact, the first identified in the near east. Large-scale reflection seismic structure shows the impact situated high on the northeastern flank of the Jordan Uplift sloping into Wadi Sirhan Basin. If exhumation is linked to the Arabia–Eurasia collision, a likely time window for the impact event may be latest Eocene to Late Oligocene. Impact into a shallow sea seems an optional scenario. Old reflection seismic lines offer limited insight into the deep structure of the rim and part of the central uplift of the complex crater. An important structural clue is provided by a well-resolved seismic horizon of a yet tentative correlation with a Paleozoic black shale. The central gravity high is compatible with a mass surplus by the uplift of denser Paleozoic basement below the central uplift. The gravity model further indicates a ring of dense Paleozoic sediments rising from below into the ring syncline. Seismics show presumably radial synclines in the central uplift which are interpreted by centripetal constrictional flow during crater collapse. Beneath the final crater’s outer boundary, a shallow-dip normal fault zone, subtle seismic structure in uncollapsed footwall segments reveal an asymmetry of strain. The asymmetry is attributed to the cratering flow by an oblique impact directed toward NE. The finding provides independent support to an earlier suggestion of impact obliquity based on vergency of folds exposed on the central uplift.

DISTRIBUTION AND PALEOECOLOGIC SIGNIFICANCE OF THE FRESHWATER DINOFLAGELLATE CYST MESSELODINIUM THIELEPFEIFFERAE GEN. ET SP. NOV FROM THE MIDDLE EOCENE OF LAKE MESSEL, GERMANY

Abstract An exploration well drilled at the Middle Eocene fossil site of Messel, near Darmstadt, Germany proved that the famous Messel oil shale was deposited in a maar lake. During a quantitative palynological investigation of the entire succession of lake sediments, a monospecific population of dinoflagellate cysts was encountered. Based on transmitted light and scanning electron microscope (SEM) studies, they are assigned to the new peridinioid taxon Messelodinium thielepfeifferae gen. et sp. nov. because they are acavate and lack distinct apical or antapical horns. The dinoflagellate cysts exhibit considerable intraspecific variation in surface ornamentation. Messelodinium thielepfeifferae gen. et sp. nov. is abundant in sediments of the early holomictic stage of Lake Messel, but generally is reduced in frequency in the oil shale which represents the meromictic stage. These dinoflagellate cysts appear in peak abundances in mass flow and debris flow deposits in which material from the lake shore was transported downslope to the basin center. Thus, major concentrations of Messelodinium thielepfeifferae gen. et sp. nov. occurred in nearshore environments either due to primary population density of the parent motile stage, or due to secondary cyst accumulation by wind and wave action. The dinoflagellate cysts are notably absent in the uppermost 25 m of the core, where Botryococcus dominates. This shift in algal populations is interpreted as a response to changes in the chemistry of the water body.

Provenance of Austroalpine basement metasediments: tightening up Early Palaeozoic connections between peri-Gondwanan domains of central Europe and Northern Africa

New U–Pb and Lu–Hf detrital zircon data together with whole-rock geochemical and Sm–Nd data were obtained for paragneisses of the Austroalpine basement south of the Tauern Window. Geochemically immature metasediments of the Northern–Defereggen–Petzeck (Ötztal–Bundschuh nappe system) and Defereggen (Drauzug–Gurktal nappe system) groups contain zircon age populations which indicate derivation mainly from Pan-African orogens. Younger, generally mature metasediments of the Gailtal Metamorphic Basement (Drauzug–Gurktal nappe system), Thurntaler Phyllite Group (Drauzug–Gurktal nappe system) and Val Visdende Formation (South Alpine Basement) were possibly derived from more distant sources. Their significantly larger abundances of pre-Pan-African zircons record a more advanced stage of downwearing of the Pan-African belts and erosion of older basement when the Austroalpine terrane was part of the Early Palaeozoic Northern Gondwana passive margin. Most zircon age spectra are dominated by Ediacaran sources, with lesser Cryogenian, Tonian and Stenian contributions and subordinate Paleoproterozoic and Neoarchean ages. These age patterns are similar to those recorded by Cambro–Ordovician sedimentary sequences in northeastern Africa between Libya and Jordan, and in some pre-Variscan basement inliers of Europe (e.g. Dinarides–Hellenides, Alboran microplate). Therefore, the most likely sources seem to be in the northeastern Saharan Metacraton and the Northern Arabian–Nubian Shield (Sinai), further supported by whole-rock Sm–Nd and zircon Lu–Hf data.

Characterizing Uranium Solubilization Under Natural Near Oxic Conditions

A solubilization study for in total 782 days using not shaken batch experiments with uranium-bearing rock and three natural carbonate minerals was conducted to characterize uranium (U) leaching under oxic conditions. Results showed that aqueous U concentration increased continuously with a solubilization rate of 0.16 ▭gm-2h-1 for the first 564 d (1.5 y). After 1.5 y, U concentration reached a maximum value (saturation) and decreased afterwards. The saturation concentration of 54 mgL-1 (mean value) was influenced to variable extent by the presence of carbonate minerals. Dissolution/precipitation, adsorption or ion exchange processes appear to control U solubilization.