The ∼2 ka subplinian eruption of Montaña Blanca,Tenerife     

G. J. Ablay  G. G. J. Ernst  J. Marti  R. S. J. Sparks 《Bulletin of Volcanology》1995,57(5):337-355

The latest cycle of volcanism on Tenerife has involved the construction of two stratovolcanoes, Teide and Pico Viejo (PV), and numerous flank vent systems on the floor of the Las Cañadas Caldera, which has been partially infilled by magmatic products of the basanite-phonolite series. The only known substantial post-caldera explosive eruption occurred 2 ka bp from satellite vents at Montaña Blanca (MB), to the east of Teide and at PV. The MB eruption began with extrusion of 0.022 km³ of phonolite lava (unit I) from a WNW-ESE fissure system. The eruption then entered an explosive subplinian phase. Over a 7–11 hour period, 0.25 km³ (DRE) of phonolitic pumice (unit II) was deposited from a 15 km high subplinian column, dispersed to the NE by 10 m/s winds. Pyroclastic activity also occurred from vents near PV to the west of Teide. Fire-fountaining towards the end of the explosive phase formed a proximal welded spatter facies. The eruption closed with extrusion of small volume domes and lavas (0.025 km³) at both vent systems. Geochemical, petrological data and Fe-Ti oxide geothermometry indicate the eruption of a chemically and thermally stratified magma system. The most mafic and hottest (875°C) unit I magma can yield the more evolved and cooler (755–825°C) phonolites of units II and III by between 7 and 11% fractional crystallization of an assemblage dominated by alkali feldspar. Analyses of glass inclusions from phenocrysts by ion microprobe show that the pumice was derived from the water-saturated roof zone of a chamber containing 3.0–4.5 wt.% H₂O and abundant halogens (F0.35wt.%). Hotter, more mafic tephritic magma intermingled with the evolved phonolites in banded pumice, indicating the injection of mafic magma into the system during or just before eruption. Reconstruction ot the event indicates a small chamber chemically stratified by in situ (side-wall) crystallization at a depth of 3–4 km below PV. Although phonolite is the dominant product of the youngest activity of the Teide-PV system, there has been no eruption of phonolitic magma for at least 500 years from teide itself and for 2000 years from the PV system. Therefore there could be a large volume of highly evolved, volatile-rich magma accumulating in these magma systems. An eruption of fluorine-rich magma comparable with MB would have major damaging effects on the island.  相似文献   

Geometry of growth strata in a transpressive fold belt in field and analogue model: Gosau Group at Muttekopf,Northern Calcareous Alps,Austria          下载免费PDF全文

Hugo Ortner  Andreas Kositz  Ernst Willingshofer  Dimitrios Sokoutis 《Basin Research》2016,28(6):731-751

The thrust sheets of the Northern Calcareous Alps were emplaced during Late Cretaceous thrust‐dominated transpression expressed by thrust sheets segmented by closely spaced tear faults. Thrust sheet‐top sediments were deposited during thrusting and associated fold growth and were controlled by active folding and tearing. We observe two types of angular unconformities: (1) Angular unconformities above folds between tear faults conform with the model of progressive unconformities. Across these unconformities dip decreases upsection. (2) Here, we define progressive unconformities that are related to tear faults and are controlled by both folding and tearing. Across these unconformities both strike and dip change. In growth strata overlying folds dissected by high‐angle faults, such unconformities are expected to be common. We used analogue modelling to define the geometry of the tear faults and related unconformities. Within the syn‐tectonic sediments, a steep, upward flattening thrust within a broader, roughly tulip‐shaped drag zone develops. The thrust roots in the tear fault in pre‐tectonic deposits and is curved upward toward the downthrown block. Vertical offset on the thrust is related to differential vertical uplift caused by, for example, growth of folds with different wavelength and amplitude on either side of the tear fault. Formation of progressive unconformities is governed by the relationship between the rates of deposition and vertical growth of a structure. Fault‐related progressive unconformities are additionally controlled by the growth of the vertical step across the tear fault. When the rates of vertical growth of two neighbouring folds separated by a tear fault are similar, the rate of growth across the tear fault is small; if the first differ, the latter is high. Episodic tear fault activity may create several angular unconformities attached to a tear fault or allow the generation of angular unconformities near tear faults in sedimentary systems that have a rate of deposition too high to generate classical progressive unconformities between the tear faults.  相似文献   

Neue Wege der geomorphologischen Forschung     

Ernst Nowack 《International Journal of Earth Sciences》1925,16(6):487-494

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Bücher- und Zeitschriftenschau     

Bubnoff  L. Rutten  Ernst Habetha  Kienow  Strassl  Konrad Richter  Stickel  Gallwitz  Wilckens 《International Journal of Earth Sciences》1937,28(8):629-641

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Production key figures for planning the mining of manganese nodules     

Sebastian Ernst Volkmann  Felix Lehnen 《Marine Georesources & Geotechnology》2018,36(3):360-375

Under the impression of decreasing ore grades and increasing production costs in conventional mining, seafloor minerals came into focus. Having gained a basic understanding of geological settings, there is still a lack of tools to assess and plan future mining projects in the deep-sea. This paper contributes to a mining concept which is inspired by the high-tech farming industry: strip mining. Potential mining fields are identified using image filters in conjunction with hydroacoustic backscatter data and slope angles and are portioned into long, narrow strips. In the framework of the EU-funded Blue Mining project, these methods were applied to a part of the eastern German exploration area, located in the manganese nodule belt of the Clarion Clipperton Zone, Pacific Ocean. Both, the mapping technique and the mining concept presented in this paper can be used in early-stage feasibility studies to derive estimates on production key figures for seafloor manganese nodule mining.  相似文献   

Glass‐bearing inclusions in Shergotty and Chassigny: Consistent samples of a primary trapped melt?          下载免费PDF全文

Maria Eugenia Varela  Ernst Zinner 《Meteoritics & planetary science》2015,50(12):2045-2066

Glass‐bearing inclusions hosted by different mineral phases in SNC meteorites provide important information on the conditions that prevailed during formation of early phases and/or on the composition of the primary trapped liquids/melts of these rocks. Although extensive previous work has been reported on such inclusions, several questions are still unresolved. We performed a chemical and petrographic study of the constituents (glasses and mineral assemblage) of glassy and multiphase inclusions in Shergotty and Chassigny. We focused on obtaining accurate trace element contents of glasses and co‐existing minerals and discussing their highly variable REE contents. Our results reveal an unusual geochemistry of trace element contents that appear to be independent of their major element compositions. Chemical equilibrium between phases inside inclusions as well as between glasses and host minerals could not be established. The LREE contents of glasses in glass inclusions can vary by up to two orders of magnitude. The depletion in trace element abundances shown by glasses seem to be inconsistent with these phases being residual melts. The light lithophile element contents of glasses are highly variable with enrichment in incompatible elements (e.g., Be, Sr, Ba, and LREE) indicating some processes involving percolation of fluids. All of these features are incompatible with glass‐bearing inclusions in the host minerals acting as closed systems preserving unmodified primary liquids/melts. Glass‐bearing inclusions in Shergotty and Chassigny appear to have been altered (as was the rock itself) by different postformational processes (e.g., shock, metamorphism, metasomatic [?] fluids) that affected these meteorites with different degree of intensity. Our results indicate that these inclusions could not preserve a reliable sample of the primary trapped melt.  相似文献   

Heterogeneities in glaciofluvial deposits using an example from new hampshire     

Sturgeon GM  Davis JM  Linder E  Harter RD 《Ground water》2006,44(4):528-539

The strong influence of subsurface heterogeneity on contaminant migration and in situ remediation calls for an improved understanding of its origins and more efficient methods of characterization. Accordingly, an outcrop study of physical and chemical heterogeneity was conducted in a glaciofluvial deposit in Deerfield, New Hampshire, in order to uncover processes controlling the spatial variation of sediment properties and evaluate the extent to which geologic information can be used to characterize the observed variation. The results indicate that physical and chemical properties at the Deerfield site have distinctly different spatial correlation structures. Lithologic facies explain 31% to 60% of the variation in permeability, dithionite citrate (DC)-extractable manganese, and DC-extractable aluminum. Lithofacies bounding surfaces do not separate regions of significantly different DC-extractable iron; instead, 49% of its variation is explained by sediment color. Color also accounts for 34% of the variation in DC-extractable aluminum and 60% of the variation in DC-extractable manganese. Strong relationships with sediment facies and/or color enable detailed mapping of permeability, extractable iron, and extractable manganese. Differences in the geometries of iron and manganese enrichment, petrographic observations, and scanning electron microscope analyses indicate that (hydr)oxide grain coatings originated from the postdepositional weathering of biotite and garnet, coupled with local, redox-driven redistribution of the liberated iron and manganese. The findings suggest that lithofacies and color information can aid the characterization and modeling of heterogeneity at similar carbon-poor glaciofluvial sites.  相似文献   

Long-term ice sheet–climate interactions under anthropogenic greenhouse forcing simulated with a complex Earth System Model     

Miren Vizcaíno  Uwe Mikolajewicz  Matthias Gröger  Ernst Maier-Reimer  Guy Schurgers  Arne M. E. Winguth 《Climate Dynamics》2008,31(6):665-690

Several multi-century and multi-millennia simulations have been performed with a complex Earth System Model (ESM) for different anthropogenic climate change scenarios in order to study the long-term evolution of sea level and the impact of ice sheet changes on the climate system. The core of the ESM is a coupled coarse-resolution Atmosphere–Ocean General Circulation Model (AOGCM). Ocean biogeochemistry, land vegetation and ice sheets are included as components of the ESM. The Greenland Ice Sheet (GrIS) decays in all simulations, while the Antarctic ice sheet contributes negatively to sea level rise, due to enhanced storage of water caused by larger snowfall rates. Freshwater flux increases from Greenland are one order of magnitude smaller than total freshwater flux increases into the North Atlantic basin (the sum of the contribution from changes in precipitation, evaporation, run-off and Greenland meltwater) and do not play an important role in changes in the strength of the North Atlantic Meridional Overturning Circulation (NAMOC). The regional climate change associated with weakening/collapse of the NAMOC drastically reduces the decay rate of the GrIS. The dynamical changes due to GrIS topography modification driven by mass balance changes act first as a negative feedback for the decay of the ice sheet, but accelerate the decay at a later stage. The increase of surface temperature due to reduced topographic heights causes a strong acceleration of the decay of the ice sheet in the long term. Other feedbacks between ice sheet and atmosphere are not important for the mass balance of the GrIS until it is reduced to 3/4 of the original size. From then, the reduction in the albedo of Greenland strongly accelerates the decay of the ice sheet.  相似文献   

Proterozoic mafic magmatism in Siberian craton: An overview and implications for paleocontinental reconstruction     

Dmitry P. Gladkochub  Sergei A. Pisarevsky  Tatiana V. Donskaya  Richard E. Ernst  Michael T.D. Wingate  Ulf Söderlund  Anatoliy M. Mazukabzov  Eugene V. Sklyarov  Michael A. Hamilton  John A. Hanes 《Precambrian Research》2010

We present a summary of late Paleoproterozoic to Neoproterozoic mafic magmatism in the Siberian craton, including recently published U–Pb and ⁴⁰Ar–³⁹Ar dates. These new precise ages suggest that at least some of the previously published K–Ar ages of Siberian mafic bodies should be ignored. The time–space geochronological chart, or the ‘barcode’ of mafic magmatic events shows significant differences between northern and southern Siberia. Both are characterized by ∼1900–1700 Ma magmatic events, but then there was an almost 1 Ga mafic magmatic ‘pause’ in south Siberia until ∼800 Ma. Meanwhile there are indications of multiple mafic magmatic events in North Siberia (Anabar shield and Olenek uplift) between ∼1600 and 1000 Ma. A series of magmatic events probably related to the breakup of Rodinia occurred in southern Siberia after ∼800 Ma. So far, there are no indications of late Neoproterozoic mafic magmatism in North Siberia. Ca. 1000–950 Ma mafic sills were reported from Meso- to Neo-Proterozoic sedimentary successions in the Sette-Daban area on the east side of the Siberian craton, but their tectonic setting is debated. Recent Ar–Ar dates of ∼1750 Ma for NW-trending dykes in the Aldan and Anabar shields, together with similar-age NNE-trending Baikal uplift dykes in south-eastern Siberia suggest the existence of a giant radial dyke swarm possibly related to a mantle plume centred in the Vilyui River area.  相似文献   

Frank J. Stadermann 1962–2010     

Ernst Zinner 《Meteoritics & planetary science》2010,45(9):1527-1528

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