Age,origin and geodynamic significance of a polymetamorphic felsic intrusion in the Ötztal Crystalline Basement,Tirol, Austria     

F. Bernhard  U. S. Klötzli  M. Thöni  G. Hoinkes 《Mineralogy and Petrology》1996,58(3-4):171-196

Summary A multi-method approach was applied to derive the age and origin of an orthogneiss body located in the central Kaunertal, western Ötztal Crystalline Basement (ÖCB). The Tieftal orthogneiss body is an internally differentiated, polymetamorphosed epizonal intrusion, embedded in amphibolites. It comprises leucocratic hedenbergite-hornblende-, hornblende- and biotite-hornblende-gneisses, but also some melanocratic rock types. The leucocratic Tieftal gneisses are granitic, have a near eutectic melt composition and share some features of A-type granites, such as high Na₂O+K₂O(8.07 to 8.58wt%), Zr (379 to 554ppm) and Y (58 to 79ppm) contents. The REE-patterns are rather flat ((La/Yb)_N=2.4 to 3.7), with distinct negative Eu anomalies. Single zircon evaporation dating of two samples and Sm-Nd dating of relict magmatic titanite resulted in ages of 487±7, 484±3 and 487±5Ma, respectively. The weighted mean of 485±3Ma is interpreted as the primary crystallization age of the Tieftal orthogneiss body. Rb-Sr whole rock dating results in a well defined regression line, corresponding to an age of 411±9Ma. This age clearly documents at least a partial resetting of the whole rock Rb-Sr system, which is most probably due to subsequent metamorphic overprint. The leucocratic Tieftal gneisses are isotopically rather primitive with an Nd _CHUR ^{485 Ma} value of +1.7 and a calculated magmatic initial⁸⁷Sr/⁸⁶Sr ratio of 0.7047. These data suggest a major mantle contribution. Most probably, they originated through fractionation of the magmatic precursors of the accompanying tholeiitic metabasites. The more primitive isotopic composition of ÖCB metabasites and some late Archean/early Proterozoic and Cambrian inheritance in Tieftal gneiss zircons suggest some involvement of old crustal rocks, too. The amount of crustal contamination can be calculated to be in the range of 10 to 40%. The Tieftal gneisses and the accompanying metabasites are interpreted as remnants of igneous rocks related to an early Ordovician rifting and incipient formation of new oceanic crust, an event which can be traced throughout the central and western European Variscan and Alpine terranes.

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Alter, Genese und geologische Bedeutung einer polymetamorphen felsischen Intrusion im Ötztalkristallin, Tirol, Österreich

Zusammenfassung Ein Vielzahl von Methoden wurde angewandt, um das Alter und die Genese eines Orthogneiskörpers im mittleren Kaunertal, westliches Ötztalkristallin, abzuleiten. Der Tieftal-Orthogneiskörper ist eine in Amphiboliten eingeschaltete, intern differenzierte, polymetamorph überprägte, epizonale Intrusion. Er umfaßt sowohl leukokrate Hedenbergit-Hornblende-, Hornblende- und Biotit-Hornblende-Gneise als auch untergeordnet melanokrate Gesteine. Die leukokraten Tieftal-Gneise besitzen einen granitischen, beinahe einer eutektischen Schmelze entsprechenden Chemismus; einige Parameter wie hohe Na₂O+K₂O(8.07 bis 8.58Gew%), Zr(379 bis 554ppm) und Y(58 bis 79ppm) Gehalte weisen auf eine A-Typ Affinität hin. Die SEE-Spektren sind nur gering fraktioniert ((La/Yb)_N=2.3 bis 3.7) und weisen eine markante negative Eu-Anomalie auf. Einzelzirkon-Evaporationsdatierungen an 2 Proben und eine Sm-Nd Datierung von reliktischem magmatischem Titanit ergeben Alter von 487±7, 484±3 und 487±5Ma. Der gewichtete Mittelwert von 485±3Ma wird als das primäre magmatische Kristallisationsalter des Tieftal-Orthogneiskörpers interpretiert. Eine Rb-Sr Gesamtgesteinsdatierung ergibt eine gut definierte Regressionsgerade mit einem Alter von 411±9Ma. Dieses Alter beweist eine postmagmatische Störung des Rb-Sr Gesamtgesteinssystems, die durch die metamorphen überprägungen verursacht wurde. Die leukokraten Tieftal-Gneise besitzen eine relative primitive isotopische Zusammensetzung mit einem Nd _CHUR ^{485 Ma} a Wert von +1.7 und einem zurückgerechneten magmatischen⁸⁷Sr/⁸⁶Sr Initialverhältnis von 0.7047. Diese Daten machen eine große Beteiligung von Mantelmaterial wahrscheinlich. Am ehesten entstanden die leukokraten Tieftal-Gneise durch magmatische Fraktionierungsprozesse aus den Ausgangsgesteinen der begleitenden tholeiitischen Metabasite. Die noch primitivere isotopische Zusammensetzung der Metabasite im Ötztalkristallin und spätarchaische/frühproterozoische sowie kambrische Komponenten in den Zirkonen der leukokraten Tieftal-Gneise weisen aber auch auf die Beteiligung alten krustalen Materials hin. Der Anteil der krustalen Komponente liegt im Bereich von 10 bis 40%. Der Tieftal-Orthogneiskörper und die begleitenden Metabasite werden als Relikte magmatischer Gesteine, die während eines frühordovizischen Riftings und der beginnenden Bildung neuer ozeanischer Kruste entstanden sind, gedeutet. Zeugen dieses Vorganges sind in allen variszisch und alpidisch geprägten Gebieten Westund Mitteleuropas zu finden.

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With 13 Figures  相似文献   

Conditions and formation mechanism of carbon phases in late quarternary geyzerites and travertines of Ol’khon area and Ol’khon Island (Baikal rift zone)     

Yu. V. Danilova  T. G. Shumilova  J. Mayer  B. S. Danilov 《Petrology》2016,24(1):35-48

Late Quaternary geyserite and travertine in Ol’khon Area and Ol’khon Island contain a recently discovered high-temperature association of hydrocarbon and carbonaceous phases, including highly crystalline graphite, α-carbyne, and bitumen, which were produced at temperatures no lower than 400°C. A carbon modification α-carbyne, which was previously found only among experimental products, was first identified in geyserite from the Ol’khon area. Nanometer-sized morphostructures and crystallites were detected on the surface of highly crystalline graphite from the geyserite and travertine. No such structures and crystallites have ever been found on graphite of magmatic, metamorphic, metasomatic, or pneumatolytic origin. The newly formed nanometer-sized morphostructures and crystallites should be regarded as typomorphic features of carbonaceous phases in high-temperature hydrothermal rocks. Graphite was likely produced in the geyserite and travertine by low-pressure polycondenssation of hydrocarbons, at free growth in open space from oversaturated solutions and/or a gas phase.  相似文献   

Real-time raster projection for web maps     

Bernhard Jenny  Bojan Šavrič  Johannes Liem 《International Journal of Digital Earth》2016,9(3):215-229

The virtual globe is the default visualization for Digital Earth applications, but it can only show one half of the Earth. This article introduces user-adjustable, on-the-fly projection of georeferenced raster images for web mapping and web GIS applications. This technique allows users to center a map on arbitrary locations, while still seeing the entire Earth surface. Modern web mapping libraries can apply map projection transformations to vector data in the browser, but they do not currently support the projection of raster images at interactive frame rates. We use the cross-platform WebGL (Web Graphics Library) graphics pipeline for hardware-accelerated projection of raster data in web browsers. Two algorithmic techniques – inverse per-fragment projection, and combined forward per-triangle and inverse per-fragment projection – for georeferenced raster imagery are documented. The resulting raster maps combine the ease of use and flexibility of interactive virtual globes with the ability to show the entire Earth. The adjustable projection of raster imagery allows users to observe global phenomena that are difficult to visualize on virtual globes or traditional maps with static projections.  相似文献   

MULTIBAND AND MULTISPECTRAL PHOTOGRAPHY FOR THE NATURAL ENVIRONMENT RESEARCH COUNCIL     

A. Mayer 《The Photogrammetric Record》1971,7(38):248-250

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Über den Zusammenhang der interdiurnen Veränderlichkeit mit der Dispersion des Luftdruckes     

R. Mayer 《Theoretical and Applied Climatology》1952,4(1):34-42

Zusammenfassung Ausgehend von einer Häufigkeitsverteilung der stündlichen Luftdruckschwankungen in der Gaußschen Form wird eine Verteilung für die täglichen Druckänderungen abgeleitet und der Zusammenhang mit der Häufigkeitsverteilung des Luftdruckes hergestellt. Dabei wird die Abhängigkeit des Mittelwertes der Druckschwankungen vom Barometerstand von Bedeutung. Eine solche empirische Ermittlung wurde für Wien in erster Näherung durchgeführt. Auf Grund des erwähnten Zusammenhanges kann die interdiurne Veränderlichkeit durch die Dispersion der Luftdruckhäufigkeitsverteilung ausgedrückt werden, was wiederum den beobachteten Parallelismus zwischen den Linien gleicher Dispersion und gleicher interdiurner Veränderlichkeit wiedergibt. Der errechnete Wert für die interdiurne Veränderlichkeit des Luftdruckes von Wien wird mit dem beobachteten verglichen.

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Summary Starting from a distribution of the hourly variations of atmospheric pressure according to Gauß a distribution for the daily variations is deduced and a connexion with the distribution of pressure is effected. With regard to these considerations the dependence of the mean value of the variations of pressure on the height of the barometer is important. In first approximation a statement of this mean value was made for Vienna. In consequence of the above mentioned connexion the mean value of the daily variations of pressure can be expressed by the dispersion of the distribution of pressure. Thus the observed parallelism between the isolines of the dispersion and those of the interdiurnal variability becomes understandable. The calculated and the observed value of the interdiurnal variability of pressu e at Vienna are compared with one another.

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Résumé Partant d'une distribution des fréquences des variations horaires de la pression atmosphérique selon la loi de Gauss, l'auteur en déduit une distribution des variations interdiurnes comparées à la distribution des fréquences de la pression elle-même. La valeur moyenne des variations de pression dépend de la hauteur barométrique. Vienne fait l'objet d'une telle recherche empirique en première approximation. Se fondant sur la relation mentionnée, on peut exprimer la variabilité interdiurne par la dispersion de la distribution des fréquences de la pression, ce qui met de nouveau en évidence le parallélisme observé entre les isolignes de la dispersion et celles de la variation interdiurne. On compare la valuer calculée de la variabilité interdiurne pour Vienne avec les valeurs observées.

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Mit 2 Textabbildungen.  相似文献   

Geomorphology,acoustic backscatter,and processes in Santa Monica Bay from multibeam mapping   总被引：2，自引：0，他引：2  

Gardner JV  Dartnell P  Mayer LA  Hughes Clarke JE 《Marine environmental research》2003,56(1-2):15-46

Santa Monica Bay was mapped in 1996 using a high-resolution multibeam system, providing the first substantial update of the submarine geomorphology since the initial compilation by Shepard and Emery [(1941) Geol. Soc. Amer. Spec. Paper 31]. The multibeam mapping generated not only high-resolution bathymetry, but also coregistered, calibrated acoustic backscatter at 95 kHz. The geomorphology has been subdivided into six provinces; shelf, marginal plateau, submarine canyon, basin slope, apron, and basin. The dimensions, gradients, and backscatter characteristics of each province is described and related to a combination of tectonics, climate, sea level, and sediment supply. Fluctuations of eustatic sea level have had a profound effect on the area; by periodically eroding the surface of Santa Monica plateau, extending the mouth of the Los Angeles River to various locations along the shelf break, and by connecting submarine canyons to rivers. A wetter glacial climate undoubtedly generated more sediment to the rivers that then transported the increased sediment load to the low-stand coastline and canyon heads. The trends of Santa Monica Canyon and several bathymetric highs suggest a complex tectonic stress field that has controlled the various segments. There is no geomorphic evidence to suggest Redondo Canyon is fault controlled. The San Pedro fault can be extended more than 30 km to the northwest by the alignment of a series of bathymetric highs and abrupt changes in direction of channel thalwegs.  相似文献   

3D visualization for pelagic fisheries research and assessment     

Mayer  Larry; Li  Yanchao; Melvin  Gary 《ICES Journal of Marine Science》2002,59(1):216-225

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The Structure of Coral Communities at Hurghada in the Northern Red Sea   总被引：1，自引：0，他引：1  

Bernhard  Riegl Branko  Velimirov 《Marine Ecology》1994,15(3-4):213-231

Abstract. The community structure of hard and soft corals, with an emphasis on hard corals, was determined by means of line-transects on 9 on-and off-shore reefs of different type and different wave exposure in the Northern Red Sea near Hurghada in Egypt. Coral communities were found to differentiate along a horizontal wind- and wave-exposure gradient. Exposed communities were dominated by Acropora species, sheltered communities by Porites species, and semi-exposed communities by Millepora species. Also, vertical within-reef zonations following a depth gradient were observed; these were unique for each exposure-determined community type. Average transect diversity was highest on semi-exposed reefs, lowest on sheltered reefs. Reef slopes were more diverse than other reef zones. The observed community structure was compared with data from the literature, and widely distributed, roughly comparable hard and soft coral communities were identified.  相似文献   

Enhanced Acoustic Backscatter Due to High Abundance of Sand Dollars, Dendraster excentricus     

Lori E. Fenstermacher  Gregory B. Crawford  Jeffry C. Borgeld  Tristan Britt  Douglas A. George  Meredith A. Klein  Neal W. Driscoll  Larry A. Mayer 《Marine Georesources & Geotechnology》2001,19(2):135-145

Detailed acoustic surveys of benthic sediments were conducted in July 1995 and September 1998 in the vicinity of Humboldt Bay, California. During these surveys, a band of enhanced acoustic backscatter was observed offshore from the bay entrance, approximately parallel to the isobaths, in water depths ranging from 16-24 m. In order to assess the cause of the increase in backscatter levels, a more comprehensive study was conducted in August and September 1999 using 100 kHz side-scan sonar, bottom grab sampling and underwater video recording. New observations indicated that a dense population of sand dollars ( Dendraster excentricus ) coincided with the enhanced backscatter band. Compared to the two previous acoustic studies, the central section of the band expanded westward by 180 m and the southern section of the band shifted eastward by 160 m, possibly resulting from a change in the biological or physical factors which influence the location and breadth of sand dollars. The relationship between high sand dollar abundance and enhanced acoustic backscatter was further verified in the nearshore region off Samoa Beach California, where a dense, banded population of sand dollars was previously observed. Video footage confirmed the presence of a band of sand dollars, also nominally parallel to the isobaths, in water depths of 8-15 m. A band of enhanced backscatter coincided with the dense sand dollar population. The identification of dense aggregations of sand dollars through enhanced acoustic backscatter could lead to the use of acoustic techniques to study sand dollar distributions and abundance.  相似文献   

The morphology and tectonics of the Mark area from Sea Beam and Sea MARC I observations (Mid-Atlantic Ridge 23° N)     

Laura S. L. Kong  Robert S. Detrick  Paul J. Fox  Larry A. Mayer  W. B. F. Ryan 《Marine Geophysical Researches》1988,10(1-2):59-90

High-resolution Sea Beam bathymetry and Sea MARC I side scan sonar data have been obtained in the MARK area, a 100-km-long portion of the Mid-Atlantic Ridge rift valley south of the Kane Fracture Zone. These data reveal a surprisingly complex rift valley structure that is composed of two distinct spreading cells which overlap to create a small, zero-offset transform or discordant zone. The northern spreading cell consists of a magmatically robust, active ridge segment 40–50 km in length that extends from the eastern Kane ridge-transform intersection south to about 23°12′ N. The rift valley in this area is dominated by a large constructional volcanic ridge that creates 200–500 m of relief and is associated with high-temperature hydrothermal activity. The southern spreading cell is characterized by a NNE-trending band of small (50–200 m high), conical volcanos that are built upon relatively old, fissured and sediment-covered lavas, and which in some cases are themselves fissured and faulted. This cell appears to be in a predominantly extensional phase with only small, isolated eruptions. These two spreading cells overlap in an anomalous zone between 23°05′ N and 23°17′ N that lacks a well-developed rift valley or neovolcanic zone, and may represent a slow-spreading ridge analogue to the overlapping spreading centers found at the East Pacific Rise. Despite the complexity of the MARK area, volcanic and tectonic activity appears to be confined to the 10–17 km wide rift valley floor. Block faulting along near-vertical, small-offset normal faults, accompanied by minor amounts of back-tilting (generally less than 5°), begins within a few km of the ridge axis and is largely completed by the time the crust is transported up into the rift valley walls. Features that appear to be constructional volcanic ridges formed in the median valley are preserved largely intact in the rift mountains. Mass-wasting and gullying of scarp faces, and sedimentation which buries low-relief seafloor features, are the major geological processes occurring outside of the rift valley. The morphological and structural heterogeneity within the MARK rift valley and in the flanking rift mountains documented in this study are largely the product of two spreading cells that evolve independently to the interplay between extensional tectonism and episodic variations in magma production rates.  相似文献