Oberkretazisches Kristallin an der Basis von Ophiolithen der Südägäis: Charakterisierung der Metamorphose-Fazies

Zusammenfassung Zur Charakterisierung der Metamorphose-Fazies des oberkretazischen Kristallins wurde ein Profil bei Lendas im Asterousia-Gebirge an der Südküste Kretas gewählt. Der Kristallin-Komplex besteht dort — vom Liegenden zum Hangenden — aus massigen Ortho-Amphiboliten, die neben Plagioklas und Magnesiohornblende Diopsid enthalten können, aus Cordierit-Granat-Sillimanit-Biotit-Gneisen sowie aus einer kalksilikatischen Serie mit salitischem Pyroxen, Pargasit, Magnesiohornblende, Cummingtonit, Granat der Grossular-Andradit-Reihe, Wollastonit und Skapolith. In die kalksilikatische Serie sind Anthophyllit, Tremolit, Olivin und Orthopyroxen führende Meta-Ultrabasite eingeschaltet.Die Mineralparagenesen in den vier klassischen Stoffbeständen — basaltisch, pelitisch, kieselig-kalkig, ultrabasisch — ermöglichen eine detaillierte Charakterisierung der Metamorphose-Fazies. An Hand dieser Paragenesen und der Mg/Fe²⁺-Verhältnisse in Cordierit und Granat wurden für die Metamorphose Temperaturen zwischen 650 und 700°C und Drucke zwischen 4 und 6 kbar abgeschätzt.

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Late Cretaceous metamorphites at the base of ophiolites in the southern aegean — characterization of the metamorphic facies

Summary Late Cretaceous metamorphites, investigated in a profile near Lendas/Asterousia Mountains (southern coast of Crete), consist of the following lithological units (from the base to the top): massive ortho-amphibolites, which may contain diopside besides plagioclase and magnesiohornblende; cordierite-garnet-sillimanite-biotite gneisses; calc-silicate rocks and marbles with salitic pyroxene, pargasite, magnesio-homblende, cummingtonite, grossular-andradite garnet, wollastonite, and scapolite. Meta-ultramafics with anthophyllite, tremolite, olivine, and orthopyroxene are intercalated with the calc-silicate series.The mineral parageneses in the four classic bulk rock compositions — basic, pelitic, siliceous-calcareous, and ultrabasic — afford an opportunity to characterize the metamorphic facies in detail. From these parageneses, and from the Mg/Fe²⁺ ratios of coexisting cordierite and garnet, temperatures between 650 and 700°C and pressures between 4 and 6 kbar have been estimated for the conditions of metamorphism.

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Mit 6 Abbildungen     

Ecological classification of macrophytes and phytobenthos for rivers in Germany according to the water framework directive

A new assessment system for macrophytes and phytobenthos in German rivers meeting the requirements of the Water Framework Directive (WFD) of the European Community is described. Biocoenotic types based on biological, chemical and hydromorphological data from over 200 river sites covering the main ecoregions, hydromorphological stream types and degradation forms have been defined. For developing a classification system the quality element macrophytes and phytobenthos was divided into three components: macrophytes, benthic diatoms and remaining phytobenthos. For macrophytes seven types including one subtype, for benthic diatoms 14 types including three subtypes and for the remaining phytobenthos five river types were identified. The benthic vegetation at reference condition was described for most of the river types. Degradation is characterised as deviation in benthic vegetation species composition and abundance from the reference biocoenosis. For classification in five ecological status classes, several metrics were developed and used in combination with existing indices. For some of the described river types additional investigations are necessary before a classification system can be developed.     

Metastable staurolite–cordierite assemblage of the Bossòst dome: Late Variscan decompression and polyphase metamorphism in the Axial Zone of the central Pyrenees

A kilometre-scale shear zone is recognized in the Cambro–Ordovician schist of the Bossòst dome, a Variscan metamorphic and structural dome in the Axial Zone of the central Pyrenees. Non-coaxial deformation is recorded by rotated garnet and staurolite porphyroblasts following regional metamorphism M₁, while coaxial conditions prevailed during later contact metamorphic M₂ growth of andalusite and cordierite. Mineral compositions and bulk rock analyses show that garnet–staurolite–andalusite–cordierite assemblages are significantly enriched in Mg and Mn over the garnet–staurolite assemblage, which lacks sufficient Mg for cordierite to form. The garnet–staurolite assemblage preserves conditions during M₁, estimated by AFM diagrams and P–T pseudosections to be 5.5 kbar and 580 °C, respectively. Pseudosections also indicate that staurolite is not a stable phase in cordierite–andalusite assemblages of M₂, suggesting polyphase metamorphism and decompression along a clockwise P–T path for the staurolite–cordierite–andalusite assemblages. This concurs with proposed extensional tectonics along the regional shear zone. To cite this article: J.E. Mezger et al., C. R. Geoscience 336 (2004).     

Isotope (O-Sr-Nd-Pb) and Fluid Inclusion Distributions in the CCSD Main Hole

1. Introduction The main-hole of the Chinese Continental Scientific Drilling Project (CCSD) in Donghai of the Dabie-Sulu UHP metamorphic belt in East China has reached its final depth of 5118 m in March 2005. As shown in Fig.     

Introduction to the special issue of the 13th International Symposium on River Sedimentation,Stuttgart, Germany: Experimental and measuring/monitoring research related to sediment issues

正The papers in this issue stem from the 13th International Symposium on River Sedimentation held in September 2016 at the University of Stuttgart,Germany.The Symposiums on River Sedimentation aim to provide a platform for scientists and engineers for fruitful and in-depth knowledge exchange.The objectives are to develop sustainable revitalization and management strategies that address the ongoing negative effects of anthropogenic activities,whilst improving river systems toward a healthy ecological status.The fundamental research and understanding of interactive     

Optimizing the yield of Sunyaev–Zel'dovich cluster surveys

We consider the optimum depth of a cluster survey selected using the Sunyaev–Zel'dovich effect. By using simple models for the evolution of the cluster mass function and detailed modelling for a variety of observational techniques, we show that the optimum survey yield is achieved when the average size of the clusters selected is close to the size of the telescope beam. For a total power measurement, we compute the optimum noise threshold per beam as a function of the beam size and then discuss how our results can be used in more general situations. As a by-product we gain some insight into what is the most advantageous instrumental set-up. In the case of beam switching observations one is not severely limited if one manages to set the noise threshold close to the point which corresponds to the optimum yield. Considering a variety of alternative scenarios, we discuss how robust our conclusions are to modifications in the cluster model and cosmological parameters. The precise optimum is particularly sensitive to the amplitude of fluctuations and the profile of the gas in the cluster.     

Niobium-tantalum Fractionation During Slab Subduction:Implications for the Formation of Continental Crust

Compared with the oceanic crust, knowledge about the formation of the continental crust (CC) is relatively poor. Although melting of subducted slabs in the early history of the Earth has been considered as the major way that shaped the chemical characteristics of the CC by most geologists, as the CC shares many characteristics with modern adakites, some geologists argued that Archean TTG was formed in the same way as modern arcs rather than slab melting, whereas others proposed that melting at the bottom of the thickened oceanic crust was more important. Recently,the debate is mainly focused on the unique subchondritic Nb/Ta value of the CC, and particularly, how Nb and Ta fractionated from each other and consequently how, in detail, the CC was built.