Ludwig Prandl†

Ohne Zusammenfassung     

Zur Kenntnis der Olivingruppe

Ohne ZusammenfassungAuszug aus einer unter der Leitung von Herrn Prof. Dr.Rudolf Mosebach fertiggestellten und im Juli 1950 abgeschlossenen Dissertation. Für zahlreiche Anregungen und tatkräftige Unterstützung gestatte ich mir auch hier meinem verehrten Lehrer herzlichst zu danken.     

Das innere Gefüge der Stauch-Endmoränen und seine Bedeutung für die Gliederung des Altmoränengebietes

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Wehrgeologie

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The marine polychaete Arenicola marina: its unusual arsenic compound pattern and its uptake of arsenate from seawater.

Arsenic compounds in the marine polychaete Arenicola marina collected from Odense Fjord, Denmark were determined by HPLC-ICPMS. In contrast to most other marine animals, A. marina contained most of its water soluble arsenic as inorganic forms, arsenite (58%) and arsenate (16%), and arsenobetaine was present as a minor constituent (6%) only. Other arsenic compounds detected in A. marina were dimethylarsinate (4%), two arsenosugars (1 and 3%), tetramethylarsonium ion (1.5%), and arsenocholine (<1%). A new arsenobetaine -trimethylarsoniopropionate-previously only reported in fish, was also present at trace levels (<1%), and an unknown anionic arsenical (approximately 10%) remains unidentified. When A. marina was exposed in laboratory experiments to different concentrations of arsenate in seawater (10, 50. 100, 500 and 1000 microg As 1(-1)) the polychaetes accumulated arsenic in a dose dependent. non-linear manner. Most of the accumulated arsenic was biotransformed to arsenite and dimethylarsinate. with the remainder being accumulated as unchanged arsenate. None of the other arsenic compounds naturally present in A. marina increased in concentration following arsenate exposure.     

Origin of the Zálesí U–Ni–Co–As–Ag/Bi deposit,Bohemian Massif,Czech Republic: fluid inclusion and stable isotope constraints

The Zálesí vein-type deposit is hosted by Early Paleozoic high-grade metamorphic rocks on the northern margin of the Bohemian Massif. The mineralization is composed of three main stages: uraninite, arsenide, and sulfide. The mineral assemblages formed at low temperatures (~80 to 130°C, locally even lower) and low pressures (<100 bars). The salinity of the aqueous hydrothermal fluids (0 to 27 wt.% salts) and their chemical composition vary significantly. Early fluids of the oldest uraninite stage contain a small admixture of a clathrate-forming gas, possibly CO₂. Salinity correlates with oxygen isotope signature of the fluid and suggests mixing of brines [δ ¹⁸O around +2‰ relative to standard mean ocean water (SMOW)] with meteoric waters (δ ¹⁸O around −4‰ SMOW). The fluid is characterized by highly variable halogen ratios (molar Br/Cl = 0.8 × 10⁻³ to 5.3 × 10⁻³; molar I/Cl = 5.7 × 10⁻⁶ to 891 × 10⁻⁶) indicating a dominantly external origin for the brines, i.e., from evaporated seawater, which mixed with iodine-enriched halite dissolution brine. The cationic composition of these fluids indicates extensive interaction of the initial brines with their country rocks, likely associated with leaching of sulfur, carbon, and metals. The brines possibly originated from Permian–Triassic evaporites in the neighboring Polish Basin, infiltrated into the basement during post-Variscan extension and were finally expelled along faults giving rise to the vein-type mineralization. Cenozoic reactivation by low-salinity, low-δ ¹⁸O (around −10‰ SMOW) fluids of mainly meteoric origin resulted in partial replacement of primary uraninite by coffinite-like mineral aggregates.     

Origin of siderite mineralisation in Petrova and Trgovska Gora Mts., NW Dinarides

The Petrova and Trgovska Gora Mts. (Gora=Mountain) are Variscan basement units incorporated into the northwestern Dinarides during the Alpine orogeny. They host numerous siderite-quartz-polysulphide, siderite-chalcopyrite, siderite-galena and barite veins, as well as stratabound hydrothermal-replacement ankerite bodies within carbonates in non-metamorphosed, flysch-like Permo-Carboniferous sequences. The deposits have been mined for Cu, Pb, Ag and Fe ores since Medieval times. Fluid inclusion studies of quartz from siderite-polysulphide-quartz and barite veins of both regions have shown the presence of primary aqueous NaCl?CaCl₂±MgCl₂?H₂O±CO₂ inclusions. The quartz-sulphide stage of both regions show variable salinities; 2.7–26.2 wt% NaCl eq. for the Trgovska Gora region and 3.4–23.4 wt% NaCl eq. for the Petrova gora region, and similar homogenisation temperatures (100–230°C). Finally, barite is precipitated from low salinity-low temperature solutions (3.7–15.8 wt % NaCl equ. and 115–145°C). P-t conditions estimated via isochore construction yield formation temperatures between 180–250°C for the quartz-sulphide stage and 160–180°C for the barite stage, using a maximum lithostatic pressure of 1 kbar (cc. 3 km of overburden). The sulphur isotope composition of barite from both deposits indicates the involvement of Permian seawater in ore fluids. This is supported by the elevated bromium content of the fluid inclusion leachates (120–660 ppm in quartz, 420–960 ppm in barite) with respect to the seawater, indicating evaporated seawater as the major portion of the ore-forming fluids. Variable sulphur isotope compositions of galena, pyrite and chalcopyrite, between ?3.2 and +2.7‰, are interpreted as a product of incomplete thermal reduction of the Permian marine sulphate mixed with organically- and pyrite-bound sulphur from the host sedimentary rocks. Ore-forming fluids are interpreted as deep-circulating fluids derived primarily from evaporated Permian seawater and later modified by interaction with the Variscan basement rocks. ⁴⁰Ar/³⁹Ar data of the detrital mica from the host rocks yielded the Variscan age overprinted by an Early Permian tectonothermal event dated at 266–274 Ma. These ages are interpreted as those reflecting hydrothermal activity correlated with an incipient intracontinental rifting in the Tethyan domain. Nevertheless, 75 Ma recorded at a fine-grained sericite sample from the alteration zone is interpreted as a result of later resetting of white mica during Campanian opening/closure of the Sava back arc in the neighbouring Sava suture zone (Ustaszewski et al. 2008).     

Evidence for an eolian origin for the silt-enriched soil mantles on the glaciated uplands of eastern Upper Michigan, USA

We provide textural, geochemical, and mineralogical data on a thin, silty deposit that unconformably mantles glaciated uplands in the eastern Upper Peninsula of Michigan. Previous research on this deposit, which we hypothesize to be loess, is nonexistent. The uplands were islands or narrow peninsulas within one or more glacial lakes. We compare the distribution, likely source and nature of the 20–60 cm thick silty mantle by using the loess formation model of Mason et al. [Mason, J.A., Nater, E.A., Zanner, C.W., Bell, J.C., 1999. A new model of topographic effects on the distribution of loess. Geomorphology 28, 223–236], which focuses on the generation of eolian silt by saltating sand across upwind, barren surfaces. Parabolic dunes, with arms open to the NW, are common on former lake floors upwind of the silt-mantled uplands, attesting to the strength and direction of paleowinds. The abrupt termination of the dunes at the footslopes of the uplands, associated with silt deposition on upland soil surfaces in downwind locations, are both consistent with the model of Mason et al. [Mason, J.A., Nater, E.A., Zanner, C.W., Bell, J.C., 1999. A new model of topographic effects on the distribution of loess. Geomorphology 28, 223−236]. Sediments on former lake floors contain abundant strata of fine/medium sand and silt, and thus are likely sources for the silt and dune sand. The cap, dune and lake sediments are similar along many different geochemical axes, whereas the substrate sediment, i.e., the drift below the cap, is unique. Cap sediments, normally containing roughly 30% silt, are enriched in quartz and depleted in Ti and Zr, relative to dune sediment. The dune sediment, a more residual eolian deposit, is enriched in Ti and Zr, relative to the cap, probably due to its greater abundance of heavy minerals. Therefore, we conclude that the silty cap is loess that was deflated from abandoned lake floors after nearby glacial lakes drained, probably contemporaneously with dune migration across the former lake floors.