Sichttiefen und Wasserfarben der oberen Seen der Feldberger Seenlandschaft im Jahre 1984 und 1985, sowie ihre Veränderungen seit 1983

A simple device is described for determining the transparency by means of white and black as well as four coloured (450, 525, 575. 625 and 720 nm) Secchi disks. The changes in transparencies and water colours having occurred in the individual years in three lakes are discussed in connection with meteorological data. The differences occurring in a groove lake between three stations indicate the differences of the development of plankton.     

Simple models for trace element fractionation during melt segregation

A dynamical calculation for melt segregation from a deformable matrix is used as a framework for studying chemical fractionation during melting and melt migration. The chemical aspects of the problem are modelled in terms of modal melting and local diffusive equilibrium, allowing for the use of unchanging distribution coefficients. The chemical properties of the melt segregated is a synthetic data set that is used to test how well simple equations for perfect equilibrium partial melt and perfect fractional partial melt recover the actual degree of melting and original source composition. The general conclusion is that either equation does quite well (to within a factor generally less than 2) even when the physical situation is quite different from that required for deriving these simple relations between degree of melting, distribution coefficient and magma composition. In terms of the apparent source composition as inferred from the properties of the segregated melt, the typical result is to find a source enriched in the more incompatible elements, which could easily be misinterpreted as requiring metasomatic alteration.     

Sichttiefen und Wasserfarben der oberen Seen der Feldberger Seenlandschaft im Jahre 1983

At the Schmaler and Breiter Luzin and at the Haus lake there were carried out monthly measurements of the depth of visibility with a white and a black Secchi disk and with Secchi disks of the colours blue, green, yellow, orange, red and reddish brown. The depths of visibility are 0.55… 5.8 m with variation widths for the colours referred to white of 0.05… 2.1 m. The diagram developed by SAUBERER , ELSTER and ?TěPÁNEK for the colour determination is extended empirically on the basis of measurements in the Feldberg lakes and then the water colour of the investigated lakes was determined in the annual variation. The thus obtained classification of the water in a ten-step scale of colours shows a good agreement with the simultaneously determined colours according to FOREL and ULE . Of particular interest is the representation of the change of colours of the three lakes in the annual variation, which shows an individual distribution of colours for each lake—proceeding from a relatively uniform colour in December.     

Zur Veränderung der Bestände von Phragmites australis (CAVANILLES) TRINIUS ex STEUDEL (Phragmites communis TRINIUS) im Breiten Luzin bei Feldberg (Mecklenburg)

This paper represents the documentation of phragmites stocks by means of photographic records with a panoramic camera (120°/45° angular coverage, f 28 mm, 1 : 2.8). There are demonstrated the changes in the stock of reed due to grazing, boat traffic, entering from the bank and passing at the back as well as the weakening of stocks under the influence of increasing nutrient contents in the water. The method allows a very efficient inspection and documentation of the hatching strips and their changes.     

Die Metarodingite der Habachformation,Hohe Tauern (Österreich)

Zusammenfassung Zwei Metarodingitvorkommen aus der Habachformation im nördlichen Vendigermassiv wurden geochemisch und petrologisch untersucht. Die Metarodingite bestehen aus Granat, Klinopyroxen und wechselnden Mengen von Titanit, Ilmenit, Epidot, Chlorit und Calcit und sind von den sie umgebenden Antigoritserpentiniten durch Blackwallbidung getrennt. Sowohl Granat als auch Klinopyroxen sind in zwei Generationen vertreten. Die ältere Generation (Grant, um 95% Grandit-Anteil mit 50–70% Andraditkomponente; Klinopyroxen, Diopsid mit 0,2–0,6% Al₂O₃) entspricht mitT=420°C beiP=2 kb dem niedriggradigen herzynischen Metamorphoseereignis, die jüngere Generation (Granat, und 90% Grandit mit 5% Andraditkomponente; Klinopyroxen, Diopsid mit bis zu 2,5% Al₂O₃), für dieT=480–500°C beiP=5 kb ermittelt werden konnten, entspricht der alpidischen Metamorphose. Mit CaO-Gehalten von bis zu 30 Gew.% und Na₂O- und K₂O-Gehalten von < 0,03 Gew.% sind die Hauptelementchernismen typisch für Rodingite, lassen aber naturgemäß keine Aussage über die Ausgangsgesteine zu. Spurenelement analysen zeigen, daß auch immobile Elemente wie Ti, Zr und Y keine sichere Abletung der Ausgangsgesteine gestatten. Dasselbe gilt für die Verteilung der REE sowie für die Cr-, Co- und Ni-Gehalte, die nur die allgemeine Aussage, daß es sich bei den Ausgangsgesteinen um Gesteine basaltischer Zusammensetzung handelt, zulassen. Stark schwankende, zum Teil sehr hohe W-Gehalte in den Metarodingiten und Blackwalls werden auf Mobilisierungen aus den, die Serpentinite umgebenden Gesteinsserien. zurückgeführt.

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The metarodingites of the Habach Formation, Hohe Tauern, Austria

Summary Geochemical and petrological investigations have been carried out on two occurrences of metarodingites from the Habach Formations within the Venediger massif, Hohe Tauern Austria. The metarodingites consitst of garnet, clinopyroxene and varying amounts of sphene, ilmenite, epidote, chlorite, and calcite. They are surrounded by antigorite-serpentinites from which they are separated by blackwall zones. Garnet and clinopyroxene are present in two generations. The older one (garnet with about 95% grandite content and 50–70% andradite; diopside with 0,2–0,6% Al₂O₃) represents the low grade Hereynian metamorphic event with an equilibration temperature of 420°C atP=2 kb. The younger generation (garnet with about 90% grandite and 5% andradite; diopside with up to 2.5% Al₂O₃) is of Alpine age and could be fixed atT=480–500°C andP=5 kb. The main element contents are typical for rodingites and show CaO-concentrations up to 30% and K₂O- as well as Na₂O-concentrations of less than 0.03%. Trace element analyses indicate that even immobile elements like Ti, Zr and Y do not allow a clear reconstruction of the original rocks from which the rodingites are derived. The same holds true for the distribution of REE-patterns and the contents of Cr, Co, and Ni. However, a primary basattic composition of the original rocks can be deducted. Additionally, there are varying, in part very high W-contents (up to 2.7% WO₃) in the metarodingites and the blackwall zones which are certainly derived by mobilisation from the surrounding rocks.

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Mit 6 Abbildungen     

Vertical distribution of phytoplankton in a stratified estuary

We present a fine vertical distribution of physico-chemical parameters and phytoplankton density around the halocline (freshwater/seawater interface) in the Krka estuary on the East coast of the Adriatic Sea. Suspended matter, surfactant activity, surface active aggregates, particulate organic carbon and phaeophytin all show largest concentrations in the 20–50 cm thick interface layer. The highest concentration of chlorophyll-a is found on the upper boundary of the interface and it is a consequence of majority of viable freshwater phytoplankton cells that accumulate there. The phytoplankton accumulates selectively in the interface: larger size fractions accumulate faster than smaller ones. In particular, nanoplanakton accumulates the least. The visible interface is also populated by dead phytoplankton cells. Most of the freshwater phytoplankton dies and decomposes in the interface, as revealed by a small chlorophyll-a/phaeophytin ratio, and it represents the main source of surface active dissolved and particulate organic matter. Marine flagellates migrate and divide in the interface, while some species likeProrocentrum micans andSyracosphera sp. are also found in the upper freshwater layer.     

Current trends in landscape research

Landscape is defined as the material-physical entity comprising the structures of nature and land use and their mutual relationship. This reduced but more precise specification of the landscape includes certain geo- and bioscientific problems as well as socio-economic conditions, motives and functions in the sense of a system approach, which have to be considered, but to do not belong to its object sphere directly. For landscape research a multi-stage procedure is introduced. It includes (a) the scientific and technical analysis of natural and land use structures inclusive their spatial and temporal dynamics (and genesis), (b) the functional analysis of landscape within the processes of socio-economic reproduction, i.e. landscape as an object of socio-economic activities and (c) the comparison of landscape structures with standardized parameters set by society under consideration of natural regularities leading to the evaluation and prognosis of these structures or certain parts of them.     

Polycyclic aromatic hydrocarbons as evidence of hydrocarbon migration in marine and lagoon sediments of a recent rift zone (Skjálfandi and Öxarfjörður), Iceland

Polycyclic aromatic hydrocarbons (PAHs) content and distribution was studied in the northern part of modern rift zone. All samples analysed represent slightly altered clastic deposits and hot water discharging in springs and from wells. To study PAH in present-day gas emission traps with diatomite absorbent were installed in the Skógalón geothermal field. All samples were analysed by the method of Shpol'sky spectroscopy. Hydrothermally altered deposits show the highest amount of PAH. Data obtained allow to believe that the distribution of PAH is closely associated with the dynamics of the hydrothermal environment. The fissure formation and temperature fluctuation in hydrothermal systems can govern both the processes of PAH synthesis and sorption. The evidences of PAH migration up through the Skjálfandi and Öxarfjörður sedimentary basins show that hydrocarbons associate mainly with hydrothermal minerals and deep ground waters. Studying PAH associations can be used as an indicator of hydrocarbons distribution, ways of migration and possible zones of accumulation in the land and marine sedimentary basins in active and ancient rift zones of Iceland.     

Magmatic history of granite-derived mylonites from the southern Desná Unit (Silesicum, Czech Republic)

Summary In the southern part of the Hruby Jeseník Mts. (Silesicum, Bohemian Massif) granitic orthogneisses and quartz-feldspars mylonites occur that were variously deformed, metamorphosed and imbricated with the overlaying Devonian volcano-sedimentary complex during the Variscan orogeny. Based on combined mapping, petrologic and geochemical studies, three main rock groups are distinguished. The fairly primitive nature of the tonalite suite is shown by low ⁸⁷Sr/⁸⁶Sr₅₅₀ ratios (0.7034–0.7038) and positive ε _Nd ⁵⁵⁰ values (+3.8 and +3.1). Isotopic composition of the metagranite suite is similar (ε _Nd ⁵⁵⁰ = +1.9 to +2.9). Both suites probably belong to a single Cadomian calc-alkaline tonalite–granite association, which can be correlated with acid-intermediate plutonic rocks of the eastern Brunovistulicum (Slavkov Terrane). All these units are interpreted as representing dismembered fragments of the same continental margin magmatic arc system. The leucogranite suite is most likely early Variscan in age. The initial Nd isotopic composition (ε _Nd ³³⁰ = +0.8 and +2.3) is consistent with its formation by a Variscan remelting of the metaigneous Cadomian crust represented by the rocks of the tonalite–granite association. The within-plate granite affinity of the leucogranite suite is most likely related to the break-up of the Brunovistulicum during the Variscan orogeny.