Geochemische Untersuchung der Eisenerzooide des Doggersandsteins im nordöstlichen Bayern

Zusammenfassung Die Mineralzusammensetzung der Nadeleisenerzooide Ostbayerns aus dem Dogger wurde optisch, röntgenographisch und die chemische Zusammensetzung spektralanalytisch ermittelt. In den Ooidkernen wurden folgende Minerale festgestellt: Nadeleisenerz, Quarz, Ilmenit und seine Verwitterungsprodukte, Zirkon, Rutil, Magnetit, Hämatit, Turmalin und Granat. In der Ooidschale wurde außer Nadeleisenerz Kaolinit (10–15%) und etwas Illit nachgewiesen.Die Art der Ooidkerne, die Festlandsnähe und die geochemischen Befunde weisen auf eine exogen sedimentäre Bildung der Eisenerzlagerstätte in dem Dogger Ostbayerns hin.     

Radiation Products in Processed Ices Relevant to Edgeworth-Kuiper-Belt Objects

Near the inner edge of the Edgeworth-Kuiper Belt (EKB) are Pluto and Charon, which are known to have N₂- and H₂O-dominated surface ices, respectively. Such non-polar and polar ices, and perhaps mixtures of them, also may be present on other trans-Neptunian objects. Pluto, Charon, and all EKB objects reside in a weak, but constant UV-photon and energetic ion radiation environment that drives chemical reactions in their surface ices. Effects of photon and ion processing include changes in ice composition, volatility, spectra, and albedo, and these have been studied in a number of laboratories. This paper focuses on ice processing by ion irradiation and is aimed at understanding the volatiles, ions, and residues that may exist on outer solar system objects. We summarize radiation chemical products of N₂-rich and H₂O-rich ices containing CO or CH₄, including possible volatiles such as alcohols, acids, and bases. Less-volatile products that could accumulate on EKB objects are observed to form in the laboratory from acid-base reactions, reactions promoted by warming, or reactions due to radiation processing of a relatively pure ice (e.g., CO → C₃O₂). New IR spectra are reported for the 1–5 mu;m region, along with band strengths for the stronger features of carbon suboxide, carbonic acid, the ammonium and cyanate ions, polyoxymethylene, and ethylene glycol. These six materials are possible contributors to EKB surfaces, and will be of interest to observers and future missions.     

Ultraviolet observations of cataclysmic variables

The preliminary results of the analysis of more than 1000 spectra of cataclysmic variables in the archive of the International Ultraviolet Explorer were presented at the meeting. To characterize the slope of the spectra I useF=log(f _1460Å/f _2880Å). For most spectraF lies between 0.2 and 0.7. No correlation of F with orbital period, inclination, system type or (for dwarf novae) length of the interoutburst interval are found, apart from somewhat lower values ofF for DQ Her type systems. Out of 16 dwarf novae for which spectra both at outburst maximum and minimum are available 11 show no large difference inF between maximum and minimum, and in 5F declines with the flux level. Out of 6 dwarf novae 5 show very red spectra during the rise to maximum, and 1 shows slopes during rise similar to those during decline.In the ultraviolet resonance lines, due to a wind from the disc, no correlation is found between inclination and terminal velocity.Paper presented at the IAU Colloquium No. 93 on Cataclysmic Variables. Recent Multi-Frequency Observations and Theoretical Developments, held at Dr. Remeis-Sternwarte Bamberg, F.R.G., 16–19 June, 1986.     

Analysis of Winter and Summer Glacier Mass Balances

Seasonal mass balance components b_w (winter balance) and b_s (summer balance) as well as c_t (total accumulation) and a_t (total ablation), can be used directly to infer climate variables. In contrast, a_c (net balance of the accumulation area) and a_a (net balance of the ablation area), and b_a or b_n (annual or net balance) can not. The traditional Alpine system of observations of a_c and a_a , however, can be converted to true seasonal values b_w and b_s if both pairs of components are simultaneously observed for some years, because a correlation between the two pairs of components exists. We analyzed b_w and b_s data and their mean, standard deviations and ratios of these to the corresponding net or annual balances for 50 glaciers with relatively long records representing different regions in the northern hemisphere. We also investigated correlations between seasonal components. A negative correlation between b_w and b_s exists at many glaciers. About two-thirds of the glaciers show insignificant correlations (?0.3 < r < 0.3), implying independence of summer and winter balances. In a few unusual cases the correlations are positive. These different correlations, or lack thereof, may offer insight into feedback conditions that must exist in this climate-related system. The correspondence of the b_w and c_t , and b_s and a_t , appears to depend largely on the relative amounts of summer snowfall, a function of their climatic environment expressed as [α = (b_w+b_s)/2]. The contribution of variability of b_s to the net balance increases markedly with decreasing values of α. The variability of b_w and b_s , and therefore the net balance, has been increasing with time; whether this is due to an increase in climate variability or to other causes is not clear. It appears that b_w has been increasing with time at the highest altitudes, but b_s has been increasing more rapidly especially at low altitudes; the many-glacier average net balance is becoming more negative.     

Pleistocene sediments of the eastern barents sea (Central Deep and Murmansk Bank Areas): Communication 1. Occurrence conditions and main structural features

The areal geological-geophysical study of Quaternary sediments was carried out in two areas of the eastern Barents Sea (Central Deep and Murmansk Bank). This communication is mainly dedicated to the results of seismoacoustic investigations. It has been established that the Quaternary sequence unconformably overlying the pre-Cenozoic strata in the studied areas is as follows (from bottom to top): marine-glaciomarine Late Glacial-Holocene sediments, massive diamictons (the main part of the section), and glaciotectonites formed after the underlying Mesozoic unconsolidated sediments. The Pleistocene diamictons, origin of which is still debatable, are the main studied object. They constitute two seismostratigraphic complexes (SSC). According to the accepted stratigraphic subdivision, they are represented by the Upper Weichselian SSC III (Maximum Last Glaciation) and Lower Weichselian SSC V (Middle Weichselian SSC IV is eroded here). Complexes SSC V and SSC III composed of till overlie the older sediments with the exaration unconformity. Complex SSC V is preserved locally, while SSC III is characterized by the regional distribution. Complex SSC III is universally enveloped unconformably without erosional surface by an acoustically uniform thin-bedded member of Late Glacial-Holocene glaciomarine and marine sediments (SSC II+I). Unlike SSC V, SSC III demonstrates lateral heterogeneity in both studied areas consisting of two seismofacies, one of which forms very specific acoustically transparent bodies (ATBs). Sediments of SSC III avoided subsequent erosion. Therefore, their glacial nature is distinctly reflected in the complex distribution of thickness and peculiar morphology of corresponding bodies.     

Environmental zonation across the Australian arid region based on long-term vegetation dynamics

Zonation of landscapes is generally based on broad scale biophysical data, field surveys, imagery and expert knowledge. Such zonation represents a static view of the environment and does not reflect dynamics and function. Arid environments are however often highly dynamic, and spatial and temporal patterns may be expressed over long periods of time. These dynamics need to be understood for management. Our aim is to understand the dynamics and functional response of vegetation in the Australian arid zone, and use this to inform and potentially improve the currently employed stratification. Principal component analysis of 25 years of satellite imagery identified underlying factors influencing patterns of arid vegetation growth, and regions of similar long-term response. Dominant factors of variation were identified as the spatial distribution of total vegetation growth, seasonality of growth, magnitude of seasonal variability in growth, and regularity of variation in growth. Additional variation resulted from episodic vegetation growth of limited spatial extent and duration. Classes expressing these functional components were compared with the existing biogeographical regions, revealing agreement in some instances, and in other cases adding information previously not available. The study demonstrates a new approach to Australian landscape zonation that has potential for much wider application.     

Assessing the water resources and ecological state of the Samur river (Eastern Caucasus)

The behavior of long-term changes in water resources of the transboundary Samur river is considered. It is found that there has been taking place a decrease in the river water flow rate over the course of the last four decades. Results from analyzing the ecological releases indicate that they would suffice to maintain the ecosystem of the river near its mouth in an acceptable state.     

Theoretical emission line strengths for Ov compared to EUV solar observations

RecentR-matrix calculations of electron impact excitation rates in Ov are used to derive the emission line intensity ratios (in energy units) $$\begin{gathered} R_1 = I(2s2p^{ 3} P - 2p^{2 3} P)/I(2s^{2 1} S_0 - 2s2p^{ 1} P_1 ) = I(761.1\mathop A\limits^ \circ )/I(629.7\mathop A\limits^ \circ ), \hfill \\ R_2 = I(2s^{2 1} S_0 - 2s2p^{ 3} P_1 )/I(2s^{2 1} S_0 - 2s2p^{ 1} P_1 ) = I(1218.4\mathop A\limits^ \circ )/I(629.7\mathop A\limits^ \circ ), \hfill \\ \end{gathered} $$ and $$R_3 = I(2s2p^{ 1} P_1 - 2p^{2 1} S_0 )/I(2s^{2 1} S_0 - 2s2p^{ 1} P_1 ) = I(774.5\mathop A\limits^ \circ )/I(629.7\mathop A\limits^ \circ )$$ as a function of electron temperature (T _e) and density (N _e). These results are presented as plots ofR ₁ vsR ₂, andR ₁ vsR ₃, which should allowboth N _e andT _e to be deduced for the Ov line emitting region of a plasma. Electron densities derived from the (R ₁,R ₂) and (R ₁,R ₃) diagrams in conjunction with observational data for several solar features obtained with the Harvard S-055 spectrometer on boardSkylab are found to be compatible, and in good agreement with values ofN _e estimated from line ratios in species formed at similar electron temperatures to Ov. In addition, values ofT _e determined from (R ₁,R ₂) and (R ₁,R ₃) are generally close to that expected theoretically. These results provide experimental support for the accuracy of the diagnostic calculations presented in this paper, and hence the atomic data used in their derivation.     

Microdiamonds — Frontier of ultrahigh-pressure metamorphism: A review

This is a comprehensive review paper devoted to microdiamonds from ultrahigh-pressure metamorphic (UHPM) terranes incorporated in orogenic belts formed at convergent plate boundaries in Paleozoic-Mesozoic-Alpine time. When in 1980 the first small diamonds were discovered within “amphibolite-granulate facies” metamorphic rocks, it came as a great surprise that buoyant continental crust could be subducted to depths of hundreds of kilometers and then subsequently exhumed. Since then, much progress has been made in understanding the mechanism of these diamonds' formation, and the number of new diamond-bearing UHPM terranes was significantly increased, especially within European orogenes. Moreover, new variations in tectonic settings in which UHP rocks can be formed and exhumed came to the attention of geologists simply due to the finding of diamonds in places previously “forbidden” for their formation—e.g., oceanic islands, ophiolites, and forearc environments. Over the past decade, the rapidly moving technological advancement has made it possible to examine microdiamonds in detail and to learn that part of them has a polycrystalline nature; that they contain nanometric, multiphase inclusions of crystalline and fluid phases; and that they keep a “crustal” signature of carbon isotopes. Scanning and transmission electron microscopy, focused-ion-beam techniques, synchrotron infrared spectroscopy, micro X-ray diffraction, and nano-secondary ion mass spectrometry studies of these diamonds provide evidence that they keep traces of fluid originated from both crustal and mantle reservoirs, and that they probably interacted with deep mantle plumes. Hypotheses proposed for diamond formation in subduction zones founded on both analytical and experimental studies are discussed. The paper also emphasizes that the discovery of these microdiamonds (as well as coesite) triggered a major revision in the understanding of deep subduction processes, leading to a clear realization of how continental materials can be recycled into the Earth's mantle and geochemically rejuvenate it.