Magma mixing,the petrogenetic link between anorthositic suites and rapakivi granites, Åland,SW Finland     

O. Eklund  S. Fröjdö  B. Lindberg 《Mineralogy and Petrology》1994,50(1-3):3-19

Summary The Åland, rapakivi batholith consists of several granites that differ texturally and mineralogically from quartz-porphyritic varieties to rapakivi varieties with K-feldspar ovoids (wiborgites and pyterlites) and aplitic granites. Closely associated with the batholith there is a mafc magmatic series of dolerite dykes, norites, anorthosites and monzodiorites.The earliest major intrusive phase of the Åland, rapakivi batholith consists of quartzporphyritic hornblende rapakivi. This rock contains small amoeboidal mafc enclaves, labradorite megacrysts, quartz ocelli, amphibole-mantled xenoliths and irregular clots of granophyric granite. These disequilibrium features are products of mixing between basaltic and granitic magmas. Geochemical modelling indicates that the quartzporphyritic hornblende rapakivi is a mixture of 15% hi-Fe monzodiorite (mafic endmember) and 85% quartz-feldspar porphyry (felsic end-member). The monzodiorite is derived from a norite-anorthosite-monzodiorite series. The quartz-feldspar porphyry is produced by partial melting of the country rock caused by intrusions of hot basic magma.Structural, textural and geochemical features suggest that magma mixing was an important petrogenetic process in the formation of the earliest rapakivi granite intrusions in the Åland, rapakivi batholith. Petrographic evidence of magma mixing can also be found in the major intrusion of the batholith, the wiborgite rapakivi granites. Chemically the mixing is difficult to specify in these rocks because of a high proportion of felsic component. Zircon and apatite fractionation trends, however, indicate that the wiborgite rapakivis also contain components from a mixed source.

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Magmamixing, die petrogenetische Verbindung zwischen Anorthositen und RapakiviGraniten, Åland, SW Finnland

Zusammenfassung Der Rapakivi Batholit von Åland besteht aus verschiedenen Graniten, die in ihrer Textur und Zusammensetzung das Feld von quarzporphyritischen über Rapakivigranite mit K-Feldspat-Ovoiden (Wiborgite und Pyterlite) und aplitischen Graniten abdecken. Eine mafische magmatische Serie von Dolerit-Gängen, Noriten, Anorthositen und Monzodioriten ist mit diesen Batholiten eng verbunden.Die erste größere Intrusivphase des Åland, Rapakivi Batholiten besteht aus quarzporphyritischem Hornblende Rapakivi. Dieses Gestein enhält kleine Amöboide, mafische Enklaven, Labradorit Megakristalle, Quarzocelli, Xenolithe mit Amphibolrändern und unregelmäßige Aggregate von granophyrischem Granit. Diese Produkte von Ungleichgewichts-Bedingungen gehen auf die Mischung zwischen basaltischen und granitischen Magmen zurück. Geochemische Modelle zeigen, daß der quarzporphyritische Hornblende-Rapakivi eine Mischung von 15%. eisenreichen Monzodiorit (mafisches Endglied) und 85% Quarz-Feldspatporphyr (felsisches Endglied) ist. Der Monzodiorit stammt von einer Norit-Anorthosit-Monzodiorit Serie. Der QuarzFeldspat-Porphyr entstand durch teilweise Aufschmelzung des Nebengesteines, die durch Intrusionen heißen basischen Magmas verursacht wurden.Strukturelle, texturelle und geochemische Daten zeigen, daß Magmamischung ein wichtiger petrogenetischer Prozeß der Bildung der frühesten Rapakivi-Granit-Intrusionen im Åland, Batholith waren. Petrographische Hinweise auf Magmamischung können auch in der größten Intrusion des Batholiths, dem Wiborg Rapakivi Granit, gefunden werden. Wegen des hohen Anteils felsischer Komponenten ist es schwierig, das Magmamixing in diesen Gesteinen chemisch zu quantifizieren. Zirkon- und Apatitfraktionierungs-Trends weisen jedoch darauf hin, daß auch die WiborgitRapakivis Komponenten aus einer gemischten Quelle enthalten.

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Grain-size-sensitive flow and shear-stress enhancement at the brittle–ductile transition of the continental crust     

Frédéric Gueydan  Yves M. Leroy  Laurent Jolivet 《International Journal of Earth Sciences》2001,90(1):181-196

Localized shear zones along low-angle normal faults have been identified in regions of extension at the brittle-ductile transition of the continental crust. The possibility of the strain localizing at a depth of 10 km is interpreted here as a consequence of an increase in the equivalent shear stress applied to the flow of the lower crust. This enhancement of the flow stress is seen as a prerequisite for the triggering of brittle deformation mechanisms leading to strain localization. The lower crust rheology used to examine this stress increase is strain-rate, temperature and grain-size dependent, due to the coupling of dislocation and diffusion creep. The model structure proposed consists of a top layer, the upper crust, gliding rigidly above a bottom layer, the lower crust, which deforms in simple shear. During a short time interval (1400 years), the equivalent shear stress is found to increase by a factor of up to 3 (67 MPa for anorthite and 17 MPa for quartz). For anorthite, this stress could explain the activation of a Mohr-Coulomb failure with a friction coefficient of 0.2, which is reasonable at the depth of 10 km. Dislocation creep is activated during a rapid change in the prescribed velocity, whereas diffusion creep dominates if the velocity is held constant, highlighting the importance of grain-size sensitivity for lower crustal rheology.  相似文献   

Geochemische Untersuchung der Eisenerzooide des Doggersandsteins im nordöstlichen Bayern     

Prof. Dr. F. Hegemann  F. Fröhlich 《Contributions to Mineralogy and Petrology》1962,8(6):393-417

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.  相似文献   

Thermomagnetic analysis of magnetite parts of serpentinite samples and results of other investigations     

Dr. H. Stiller  Dr. Dr. F. Frölich Dipl.-Geophys.  F. Ch. Wagner 《Pure and Applied Geophysics》1961,49(1):129-136

Summary The normal type of serpentinites consists of chrysotile. The magnetite parts are essential parts of the structure of chrysotile serpentinites (primary magnetite). Chrysotile is changed to antigorite by mechanical deformations. The magnetite parts of rock structure are lost and they sat down in the veins of serpentinite rocks (secondary magnetite). In this paper the thermomagnetic diagrams and the results of X-ray investigations of secondary and primary magnetite are described. Some results of susceptibility measurements are given. The secondary magnetite is characterized by a region of oxydation in the interval 280–400° C (secondary magnetite-Fe₂O₃-Fe₂O₃). The oxydation to -Fe₂O₃ is remarkably. On the thermomagnetic diagrams of primary magnetite no typical oxydation region is to be seen. The oxydation: primary magnetite-Fe₂O₃ is very small. The interval of measured susceptibility values amounts to (10–1500)·10^–6 cgs units. The essential variability of the main parts of serpentinite samples is characterized by the great changes of susceptibility values from point to point.The determined values of specific saturation magnetization (Gauss. cm³ g^–1), the X-ray powder data, and some results on remanent magnetization are given.

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Zusammenfassung Die Normaltypserpentinite bestehen aus Chrysotil. Der Magnetit ist Bestandteil der Struktur der Chrysotilserpentinite (primärer Magnetit). Unter dem Einfluß mechanischer Deformationen geht Chrysotil in Antigorit über. Die Magnetitanteile der Gesteinsstruktur gehen verloren und scheiden sich auf Klüften ab (sekundärer Magnetit). In der vorliegenden Arbeit werden die thermomagnetischen Abhängigkeiten und die Ergebnisse von Röntgenuntersuchungen des sekundären und primären Magnetits beschrieben. Es werden einige Ergebnisse der Suszeptibilitätsmessungen angeführt. Der sekundäre Magnetit wird durch einen Oxydationsbereich im Temperaturintervall 280–400° C charakterisiert (sekundärer Magnetit-Fe₂O₃-Fe₂O₃). Die Oxydation zu -Fe₂O₃ ist beträchtlich. Die thermomagnetischen Diagramme des primären Magnetits zeigen keinen typischen Oxydationsbereich. Die Oxydation: primärer Magnetit-Fe₂O₃ ist sehr gering. Das Intervall der gemessenen Suszeptibilitätswerte beträgt (10–1500)·10^–6 CGS-Einheiten. Die starke Veränderlichkeit der Hauptbestandteile der Serpentinitproben wird durch die großen Änderungen der Suszeptibilitätswerte von Punkt zu Punkt gekennzeichnet.Die gemessenen Werte der Sättigungsmagnetisierung (Gauss.cm³ g^–1), der Röntgenuntersuchungen und einige Ergebnisse über die remanente Magnetisierung werden gegeben.

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Neuere Veröffentlichungen     

Fr. Model 《Ocean Dynamics》1959,12(1):34-36

Ohne Zusammenfassung  相似文献   

Neuere Veröffentlichungen     

Fr. Model  H. Weidemann  K. Kalle 《Ocean Dynamics》1959,12(3):130-132

Ohne Zusammenfassung  相似文献   

Hydrographische Bibliographie     

Fr. Model  H. Mädler 《Ocean Dynamics》1968,21(1):27-48

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Neuere Veröffentlichungen     

H. Ermel  W. Kuntze  Fr. Model  F. Schüler 《Ocean Dynamics》1955,8(2):77-79

Ohne Zusammenfassung  相似文献   

The use of transplanted cultured tropical oysters (Saccostrea commercialis) to monitor Cd levels in North Queensland coastal waters (Australia)     

Olivier F  Ridd M  Klumpp D 《Marine pollution bulletin》2002,44(10):1051-1062

Bivalves are commonly used to detect metal pollution in the marine environment. Commercially cultured Milky oysters (Saccostrea commercialis) were transplanted in various sites along the North Queensland coast and analyzed for two metals of potentially anthropogenic origin (Cd, Zn). To provide additional information, naturally occurring Black Lip oysters (Saccostrea echinata) were also collected at the transplantation sites. The study demonstrated that the oysters species transplanted are good bioindicators of these metal concentrations in tropical waters, sensitive to variations in the environment at concentrations which are much smaller than pollution signals commonly reported for temperate waters. Three transplant experiments were carried out from May 1999 to February 2000. Milky oysters transplanted to offshore areas (Orpheus Is., Kelso Reef) accumulated Cd in the soft parts whereas oysters sampled from cages placed in Ross Creek and the Herbert River estuaries showed a decrease in Cd concentration, which resulted from an increase in dry weight. Dry weight appeared to be an important covariant affecting Cd concentration in the oysters whereas it does not unambiguously affect Zn concentrations. For the duration of the experiments, oysters sampled from the Magnetic Is. reference site showed effectively constant Cd concentrations and total Cd contents which indicates that any seasonal cycle affecting metal concentration is weak. It was found that Cd accumulation in oysters increased as ambient dissolved Cd concentration decreased, from which it was concluded that for these oysters, the predominant source of Cd was from the particulate phase rather than the dissolved phase.  相似文献   

The LMDZ4 general circulation model: climate performance and sensitivity to parametrized physics with emphasis on tropical convection   总被引：3，自引：11，他引：3  

Frédéric Hourdin  Ionela Musat  Sandrine Bony  Pascale Braconnot  Francis Codron  Jean-Louis Dufresne  Laurent Fairhead  Marie-Angèle Filiberti  Pierre Friedlingstein  Jean-Yves Grandpeix  Gerhard Krinner  Phu LeVan  Zhao-Xin Li  François Lott 《Climate Dynamics》2006,27(7-8):787-813

The LMDZ4 general circulation model is the atmospheric component of the IPSL–CM4 coupled model which has been used to perform climate change simulations for the 4th IPCC assessment report. The main aspects of the model climatology (forced by observed sea surface temperature) are documented here, as well as the major improvements with respect to the previous versions, which mainly come form the parametrization of tropical convection. A methodology is proposed to help analyse the sensitivity of the tropical Hadley–Walker circulation to the parametrization of cumulus convection and clouds. The tropical circulation is characterized using scalar potentials associated with the horizontal wind and horizontal transport of geopotential (the Laplacian of which is proportional to the total vertical momentum in the atmospheric column). The effect of parametrized physics is analysed in a regime sorted framework using the vertical velocity at 500 hPa as a proxy for large scale vertical motion. Compared to Tiedtke’s convection scheme, used in previous versions, the Emanuel’s scheme improves the representation of the Hadley–Walker circulation, with a relatively stronger and deeper large scale vertical ascent over tropical continents, and suppresses the marked patterns of concentrated rainfall over oceans. Thanks to the regime sorted analyses, these differences are attributed to intrinsic differences in the vertical distribution of convective heating, and to the lack of self-inhibition by precipitating downdraughts in Tiedtke’s parametrization. Both the convection and cloud schemes are shown to control the relative importance of large scale convection over land and ocean, an important point for the behaviour of the coupled model.  相似文献