Das geochemische Verhalten des Strontiums bei der Genese und Diagenese von Ca-Karbonat- und Ca-Sulfat-Mineralen     

Eberhard Usdowski 《Contributions to Mineralogy and Petrology》1973,38(3):177-195

Experimental partioning of Sr between solutions, aragonite, calcite, gypsum and anhydrite show that the isomorphous replacement of Ca²⁺ by Sr²⁺ can be described as a linear function. The constants of the distributions are used to calculate primary Sr-contents of the various Ca-carbonates and Ca-sulfates precipitated from seawater and to estimate the point of precipitation of celestite. Comparism of these data with actual Sr-contents in sediments and sedimentary rocks show that in most cases gypsum has to be considered as the primary precipitate. Anhydrite in general is formed by diagenetic alteration of gypsum. The average Sr-content of gypsum rocks make it very probable that the Sr-concentration of seawater has stayed virtually unchanged since the end of Mesozoic. Sr-contents of carbonate rocks show that most of the limestones have been altered diagenetically. The distribution of Sr within the various sedimentary units of the earth's crust make it very probable that this alteration occurred in a system open to pore solutions.  相似文献   

Die Rolle der Strukturänderung und Mischkristallentwicklung bei der Deutung der Differentiation und Kristallisation vulkanischer Gesteine     

Eberhard Kramer Dipl.-Min. 《International Journal of Earth Sciences》1967,57(1):335-348

Zusammenfassung Es wird ein Überblick über die Änderung des Gefüges und der Mischkristalle einer Generation vulkanischer Gesteine gegeben. Die Gesteinsproben lassen sich nach ihren Einsprenglingen in eine genetische Reihenfolge der Schmelzentwicklung gliedern und zeigen dabei eine kontinuierliche Veränderung der Mischkristallphasen der Grundmasse. An Meßreihen für Olivin, Plagioklas und Sanidin und an der Verschiebung der Röntgenreflexe ist dieser Phasenwandel nachgewiesen. Zwölf Abbildungen zeigen den Übergang des Mineralbestandes und des Gefüges in der Grundmasse von Probe zu Probe.

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A survey of the changes of the structure and of the mixed crystals in a generation of volcanic rocks is given. According to their accessory minerals (Einsprengunge) the rock samples can be arranged in a genetic sequence of the melting-process; in this they show a continuous change in the phases of mixed crystals of the ground-mass. This change of phase is demonstrated by measuring sequences for Olivine, Plagioclase and Sanidine and by shift of the X-ray reflexes. Twelve figures show the transition of the mineral stock and of the structure in the ground-mass from sample to sample.

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Résumé Une vue d'ensemble sur les changes de structure et des cristaux composés d'une génération de roches volcaniques est présentée. Les spécimens de roches peuvent être organisés — selon leurs phénocrystaux — dans une série génétique du procès de fusion; ils montrent une change continuelle des phases de cristaux composés de la matrice. La change des phases ist prouvée par mesurages en séries et par le déplacement des reflexes radiographiques. Douze figures montrent la transition du dépót de minéraux et de la structure dans la matrice d'un spécimen à l'autre.

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Eo-alpine metamorphism in the uppermost unit of the Cretan nappe system — Petrology and geochronology     

Eberhard Seidel  Martin Okrusch  Hans Kreuzer  Helmut Raschka  Wilhelm Harre 《Contributions to Mineralogy and Petrology》1981,76(3):351-361

The uppermost unit of the Cretan nappe system consists of ophiolites on the top, and an ophiolitic mélange at the base.Among the various constituents of the mélange, there are slices of low-P/high-T metamorphics. They form a variegated series consisting of tholeiitic ortho-amphibolites, para-amphibolites, andalusite and sillimanite-cordierite-garnet bearing mica schists, calcsilicate rocks, and marbles. The metamorphic sequence is locally intruded by early tectonic magmatites of gabbroic, dioritic and granitic composition. Critical mineral assemblages lead to a maximum temperature of about 700° C reached during metamorphism, at a total pressure of 4–5 kilobars. K — Ar dating on 6 hornblendes, 7 biotites and 1 muscovite yielded cooling ages of 75–66 m.y. and confirmed earlier results according to which the metamorphism and related magmatism took place in Late Cretaceous times.In order to evaluate the age relationships between the hightemperature metamorphics within the ophiolitic mélange and the ophiolites, hornblendes from ultramafic and mafic rocks of the ophiolite complex were dated by the K — Ar method. Hornblende from one schistose hornblendite forming a constituent of the ophiolites proper yielded 156 m.y. and thus provides a middle Jurassic minimum age for the formation of this piece of oceanic lithosphere. Four hornblendes of calc-alkaline gabbrodiorite dikes within the ophiolite complex gave distinctly lower K — Ar dates of about 140 m.y.. The dikes probably intruded after the detachment of the ophiolites in an island-arc or continental-margin environment.As a consequence, the high-temperature metamorphics and related intrusives in the ophiolitic mélange of Crete are genetically unrelated to the overlying ophiolites. The paleogeographic position of the crystalline terrane, slices of which are now incorporated into the ophiolitic mélange is still open to discussion.  相似文献   

Geochronology of high-pressure rocks on Sifnos (Cyclades,Greece)     

Rainer Altherr  Manfred Schliestedt  Martin Okrusch  Eberhard Seidel  Hans Kreuzer  Wilhelm Harre  Heinz Lenz  Immo Wendt  Günther A. Wagner 《Contributions to Mineralogy and Petrology》1979,70(3):245-255

Polymetamorphic rocks of Sifnos (Greece) have been investigated by Rb-Sr, K-Ar, and fission track methods. Critical mineral assemblages from the northern and southernmost parts of Sifnos include jadeite+quartz+3T phengite, and omphacite+garnet +3T phengite, whereas the central part is characterized by the assemblage albite+chlorite+epidote+2M ₁ phengite.K-Ar and Rb-Sr dates on phengites (predominantly 3T) of the best preserved high P/itTmetamorphic rocks from northern Sifnos gave concordant ages around 42 m.y., indicating a Late Lutetian age for the high P/T metamorphism. Phengites (2M ₁+3T) of less preserved high P/T assemblages yielded K-Ar dates between 48 and 41 m.y. but generally lower Rb-Sr dates. The higher K-Ar dates are interpreted as being elevated by excess argon.K-Ar and Rb-Sr ages on 2M ₁ phengites from central Sifnos vary between 24 and 21 m.y. These ages date a second, greenschist-facies metamorphism which overprinted the earlier high-pressure metamorphic rocks.  相似文献   

Paläoklimatische Information im Isotopengehalt14C-datierter Saharawässer: Kontinentaleffekt in D und18O     

Dr. Christian Sonntag  Prof. Dr. Eberhard Klitzsch  Prof. Dr. E. M. El Shazly  Christel Kalinke  Prof. Dr. Karl Otto Münnich 《International Journal of Earth Sciences》1978,67(2):413-423

Zusammenfassung In den¹⁴C-Altern der Saharawässer spiegelt sich die wechselnde Abfolge von Feucht- und Trockenphasen während des späten Pleistozäns und Holozäns wider. Außerdem zeigt sich ein West-Ost-Gefälle in ihrem D- und¹⁸O-Gehalt, das als Kontinentaleffekt im Grundwasser gedeutet wird. Dieser Kontinentaleffekt setzt voraus, daß das nordafrikanische Klimageschehen vergangener Feuchtphasen von der Westdrift bestimmt wurde, die regenbringende atlantische Luftmassen weit ins Saharainnere getrieben hat. Ein einfaches mathematisches Modell, das den Kontinentaleffekt durch eine Rayleigh-Kondensation beschreibt, ergibt die beste Anpassung an die Meßwerte, wenn für die Sahara (ähnlich wie heute in Europa) ein West-Ost-Gefälle in den Paläo-Winterniederschlagsmengen von –30% pro 1000 km angenommen wird. Unter der Annahme ehemaliger Winterniederschläge (Sept.-März) von 600 mm (entspricht Lissabon heute) für das Gebiet an der nordafrikanischen Atlantikküste ergibt diese Modellrechnung z. B. 250 mm für die Paläo-Winterniederschläge im Gebiet des Murzuk-Beckens.

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The¹⁴C-age distribution of Saharian groundwaters shows the alternating sequence of humid and arid periods in the late Pleistocene and Holocene. The observed west-east decrease of the D- and¹⁸O-content of the Sahara waters is interpreted to be the Continental Effect in rain and groundwater. The paleoclimatic situation during ground-water formation therefore was controlled by the western drift carrying wet Atlantic air masses across the Sahara. The best fit of a simple Rayleigh condensation model of the continental effect to the experimental data is obtained with a west-east decrease of the Saharian paleo-winter precipitation of –30% per 1000 km (similar to the one in Europe today). With an annual winter precipitation rate (Sept.-March) of 600 mm (corresponding to the one of Lisboa today) for the Northafrican coastal area at the Atlantic Ocean a previous winter precipitation rate of 250 mm is obtained for the Murzuq Basin.

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Résumé Une succession de périodes humides et arides à la fin du Pléistocène et à l'Holocène se réflète dans la distribution des âges¹⁴C d'eaux souterraines du Sahara. Les teneurs en D et¹⁸O diminuent d'Ouest en Est, ce qui est interprété comme un effet continental dans l'eau souterraine. Celui-ci signifie que la climatologie des phases pluviales passées, dans l'Afrique du Nord, était déterminée par des vents d'Ouest qui apportaient des masses d'air atlantique humide à l'intérieur du Sahara. Un modèle mathématique simple décrivant l'effet continental par une condensation du type Rayleigh, reproduit avec la meilleure conformité les valeurs expérimentales, pour autant qu'on admette que les pluies hivernales au Sahara diminuaient anciennement d'Ouest en Est de 30% par 1000 km (comme à présent en Europe). En supposant qu'autrefois la quantité de pluie hivernale, de septembre à mars à la côte atlantique de l'Afrique du Nord était de 600 mm (comme aujourd'hui à Lisbonne), on obtient à l'aide de ce modèle une précipitation hivernale ancienne de 250 mm dans le bassin du Mourzouk.

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Chloritoid-bearing metapelites associated with glaucophane rocks in western Crete,Greece     

Eberhard Seidel  Martin Okrusch 《Contributions to Mineralogy and Petrology》1977,60(3):321-324

Problems related to the formation of chloritoid in metapelites, associated with lawsonite-glaucophane bearing metabasalts, in the quartzitephyllite series of western Crete (Greece) are discussed. It is supposed that chloritoid was formed, during prograde metamorphism, according to a gliding-equilibrium reaction of the type (Fe,Mg)-carpholite₁+chlorite₁ (Fe,Mg)-carpholite_{1 2}+(Fe,Mg)-chloritoid_{1 2} +chlorite_1→2+quartz+H₂O ? (Fe,Mg)-chloritoid₂+chlorite₂+quartz+H₂O. This view is stipulated by the occurrence of ferrocarpholite-chloritoid schists in the southeastern part of central Crete. The assemblage chloritoid+ lawsonite recently recognized in western Crete provides evidence that the formation of chloritoid started well within the stability field of lawsonite.  相似文献   

Tectono‐sedimentary evolution of lower to middle Miocene half‐graben basins related to an extensional detachment fault (western Crete,Greece)     

Markus Seidel  Eberhard Seidel  Bernhard Stckhert 《地学学报》2007,19(1):39-47

Crustal extension in the overriding plate at the Aegean subduction zone, related to the rollback of the subducting African slab in the Miocene, resulted in a detachment fault separating high‐pressure/low‐temperature (HP‐LT) metamorphic lower from non‐metamorphic upper tectonic units on Crete. In western Crete, detachment faulting at deeper crustal levels was accompanied by structural disintegration of the hangingwall leading to the formation of half‐graben‐type sedimentary basins filled by alluvial fan and fan‐delta deposits. The coarse‐grained clastic sediments in these half‐grabens are exclusively derived from the non‐metamorphic units atop the detachment fault. Being in direct tectonic contact with HP‐LT metamorphic rocks of the lower tectonic units today, the basins must have formed in the period between c. 20 and 15 Ma, prior to the exposure of the HP‐LT metamorphic rocks at the surface, and juxtaposed with the latter during ongoing deformation.  相似文献   

The Contribution of Asteroid Dust to the Interplanetary Dust Cloud: The Impact of ULYSSES Results on the Understanding of Dust Production in the Asteroid Belt and of the Formation of the IRAS Dust Bands     

Ingrid Mann  Eberhard Grün  Martin Wilck 《Icarus》1996,120(2):399-407

Investigations of the zodiacal dust cloud give evidence for a significant contribution of asteroidal dust to the interplanetary dust cloud, a result which can now be compared to measurements of the ULYSSES dust detector during its passage of the asteroid belt. Especially we discuss the ULYSSES data with respect to the IRAS dust bands and consider geometric selection effects for the detector. From calculations of radiation pressure forces, we conclude that particles in the IRAS dust bands with massesm≥ 10⁻¹²g will stay in bound orbits after their release from asteroid fragmentation. This is already in the mass range (10⁻¹⁶–10⁻⁷g) of particles detectable with the dust detector onboard ULYSSES. The absence of these particles in the ULYSSES data cannot be explained exclusively in terms of their small detection probability. Thus we conclude that the size distribution of particles in the IRAS dust bands most probably cannot be continued to the submicrometer range. Concerning the global structure of the inner zodiacal cloud (i.e., about solar distancer< 3.5 AU) the ULYSSES data are not inconsistent with present models. Recent estimates of the total mass of the interplanetary cloud require a dust production rate of about 10¹⁴g/year of which a significant amount is assumed to result from the asteroids. Our estimate for the production of dust particles in an IRAS dust band, based on the assumption that the dust band results from a single destruction of an asteroid of 100 km size, yields a production rate of 10¹⁰g/year. Other models of the IRAS dust bands suggest production rates up to 10¹²g/year and also cannot provide a significant source of the dust cloud.  相似文献   

SUJETS A TRAITER POUR L'ASSEMBLÉE DE 1960     

Dr.-Ing. Dieter LAUTERBACH  Eberhard GLOS 《水文科学杂志》2013,58(3):9-12

ABSTRACT

The present paper reports on some practical experiences gained in computing unit hydrographs (UH) according to the “classical” linear theory. The sizes of the drainage basins varied from 50 to 800 km² of hilly country.  相似文献   

Long-term passive distance-bounded relative motion in the presence of J_2 perturbations     

Jing Chu  Jian Guo  Eberhard K. A. Gill 《Celestial Mechanics and Dynamical Astronomy》2015,121(4):385-413

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