Rutile inclusions in garnet from a dissolution‐reprecipitation mechanism     

Shyh‐Lung Hwang  Pouyan Shen  Hao‐Tsu Chu  Tzen‐Fu Yui  Yoshiyuki Iizuka  Hans‐Peter Schertl 《Journal of Metamorphic Geology》2019,37(8):1079-1098

Metamorphic garnet commonly contains needle‐like rutile inclusions as well as equant rutile inclusions that surround quartz inclusions and range in size from submicrometer to nanometer. Although the origin of these equant rutile inclusions, that is, exsolution or non‐exsolution, has important implications for petrological and tectonic processes, the crystallographic characteristics of these inclusions have rarely been studied because of the small sizes and analytical difficulties involved. Here, we report the crystallographic characteristics pertinent to the genetic origin of minute equant rutile inclusions in cloudy, nearly spherically shaped garnet domains with Ti‐depleted compositions surrounding quartz inclusions in ultrahigh‐pressure garnet from several diamondiferous Erzgebirge quartzofeldspathic gneissic rock samples. TEM analyses show that the equant rutile crystals in cloudy garnet domains are partially bounded by the low‐energy {100}_rt ± {110}_rt ± {101}_rt facets and have rather random crystallographic orientation relationships (CORs) with the garnet host, with preferential alignment of low‐energy lattice planes, for example, {100}_rt//{112}_grt, for some rutile crystals. Although the rather random CORs are unlikely to be attributed to solid‐state exsolution subjected to the stringent topotactic garnet lattice constraints, the characteristic subhedral {100}_rt ± {110}_rt ± {101}_rt crystal forms of rutile can be rationalized by a metasomatic dissolution‐reprecipitation mechanism via a fluid phase. In this scenario, the quartz+fluid inclusions in garnet were first subjected to decompression microcracking during rock exhumation, followed by dissolution of Ti‐bearing garnet matrix at the crack tips or along the crack surfaces and subsequent reprecipitation of rutile, apatite, gahnite, akdalaite, and Ti‐depleted garnet. The rapid coalescence between rutile and garnet crystals in fluid or direct attachment of rutile crystals onto the dissolving crack surfaces would then yield the rather random CORs as reported here. These results, along with previous work on rutile needles, indicate rather diverse genesis of rutile inclusions in various crystal forms, thus shedding light on the controversial exsolution origin for other inclusion suite/microstructure in minerals.  相似文献   

Why chromatic imaging matters     

Joel Sanchez-Bermudez  Florentin Millour  Fabien Baron  Roy van Boekel  Laurent Bourgès  Gilles Duvert  Paulo J. V. Garcia  Nuno Gomes  Karl-Heinz Hofmann  Thomas Henning  Jacob W. Isbell  Bruno Lopez  Alexis Matter  J-Uwe Pott  Dieter Schertl  Eric Thiébaut  Gerd Weigelt  John Young 《Experimental Astronomy》2018,46(3):457-473

During the last two decades, the first generation of beam combiners at the Very Large Telescope Interferometer has proved the importance of optical interferometry for high-angular resolution astrophysical studies in the near- and mid-infrared. With the advent of 4-beam combiners at the VLTI, the u ? v coverage per pointing increases significantly, providing an opportunity to use reconstructed images as powerful scientific tools. Therefore, interferometric imaging is already a key feature of the new generation of VLTI instruments, as well as for other interferometric facilities like CHARA and JWST. It is thus imperative to account for the current image reconstruction capabilities and their expected evolutions in the coming years. Here, we present a general overview of the current situation of optical interferometric image reconstruction with a focus on new wavelength-dependent information, highlighting its main advantages and limitations. As an Appendix we include several cookbooks describing the usage and installation of several state-of-the art image reconstruction packages. To illustrate the current capabilities of the software available to the community, we recovered chromatic images, from simulated MATISSE data, using the MCMC software SQUEEZE. With these images, we aim at showing the importance of selecting good regularization functions and their impact on the reconstruction.  相似文献   

GPS for real-time earthquake source determination and tsunami warning systems   总被引：1，自引：0，他引：1  

Geoffrey Blewitt  William C. Hammond  Corné Kreemer  Hans-Peter Plag  Seth Stein  Emile Okal 《Journal of Geodesy》2009,83(3-4):335-343

We identify the key design aspects of a GPS-based system (and in the future, GNSS-based systems) that could contribute to real-time earthquake source determination and tsunami warning systems. Our approach is based on models of both transient and permanent displacement of GPS stations caused by large earthquakes, while considering the effect of GPS errors on inverted earthquake source parameters. Our main conclusions are that (1) the spatial pattern, magnitude, and timing of permanent displacement of GPS stations can be inverted for the earthquake source and so predict the 3D displacement field of the ocean bottom, thus providing the initial conditions for tsunami models, and (2) there are no inherently limiting factors arising from real-time orbit and positioning errors, provided sufficient near-field GPS stations are deployed. This signal could be readily exploited by GPS networks currently in place, and will be facilitated by the IGS Real-Time Project as it comes to fruition.  相似文献   

Diffusion of divalent cations in garnet: multi-couple experiments   总被引：1，自引：1，他引：0  

A. L. Perchuk  M. Burchard  H.-P. Schertl  W. V. Maresch  T. V. Gerya  H.-J. Bernhardt  O. Vidal 《Contributions to Mineralogy and Petrology》2009,157(5):573-592

We demonstrate the possibility of studying several diffusion couples in a single run, i.e. under almost similar P–T–t– conditions, allowing direct comparison of the diffusion rates in different diffusion couples. Thus the duration of experimental study and the risk of failure of expensive experimental equipment can be decreased considerably. The diffusion experiments were carried out in piston-cylinder apparatus. Gem-quality garnets of almandine, spessartine and grossular compositions together with inclusion-rich eclogitic garnets were embedded in a powder of natural pyrope and annealed together under dry conditions at P = 1.9–3.2 GPa and T = 1,070–1,400°C. Diffusion profiles were measured by electron microprobe and fitted numerically on the basis of multicomponent diffusion theory. The datasets derived from different diffusion couples yields parameters of the Arrhenius equation for Ca, Mg and Fe in natural eclogitic garnets and Mg, Mn and Fe in gem-quality garnets. We have also studied the effect of grain-boundary diffusion in the sintered pyrope matrix on interdiffusion on the basis of 2D modeling. Under conditions analogous to those of our experimental runs, we show that observed irregularities in some measured diffusion profiles (not applied for the diffusion modeling) can be directly related to the superposition of local grain-boundary diffusion on dominant volume diffusion.  相似文献   

Mantle circulation models with variational data assimilation: inferring past mantle flow and structure from plate motion histories and seismic tomography   总被引：3，自引：0，他引：3  

Hans-Peter Bunge  C. R. Hagelberg  B. J. Travis 《Geophysical Journal International》2003,152(2):280-301

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Chemical Mechanism Development: Laboratory Studies and Model Applications     

Harald Geiger  Ian Barnes  Karl H. Becker  Birger Bohn  Theo Brauers  Birgit Donner  Hans-Peter Dorn  Manfred Elend  Carlos M. Freitas Dinis  Dirk Grossmann  Heinz Hass  Holger Hein  Axel Hoffmann  Lars Hoppe  Frank Hülsemann  Dieter Kley  Björn Klotz  Hans G. Libuda  Tobias Maurer  Djuro Mihelcic  Geert K. Moortgat  Romeo Olariu  Peter Neeb  Dirk Poppe  Lars Ruppert  Claudia G. Sauer  Oleg Shestakov  Holger Somnitz  William R. Stockwell  Lars P. Thüner  Andreas Wahner  Peter Wiesen  Friedhelm Zabel  Reinhard Zellner  Cornelius Zetzsch 《Journal of Atmospheric Chemistry》2002,42(1):323-357

Within the German Tropospheric Research Programme (TFS) numerous kinetic and mechanistic studies on the tropospheric reaction/degradation of the following reactants were carried out: oxygenated VOC, aromatic VOC, biogenic VOC, short-lived intermediates, such as alkoxy and alkylperoxy radicals.At the conception of the projects these selected groups were classes of VOC or intermediates for which the atmospheric oxidation mechanisms were either poorly characterised or totally unknown. The motivation for these studies was the attainment of significant improvements in our understanding of the atmospheric chemical oxidation processes of these compounds, particularly with respect to their involvement in photooxidant formation in the troposphere. In the present paper the types of experimental investigations performed and the results obtained within the various projects are briefly summarised. The major achievements are highlighted and discussed in terms of their contribution to improving our understanding of the chemical processes controlling photosmog formation in the troposphere.  相似文献   

Das Verhältnis TiO2 : Fe in westnorwegischen Magn etit-Ilmeniterzen     

Dr. Hans-Peter Geis 《International Journal of Earth Sciences》1966,55(2):414-417

Zusammenfassung In Westnorwegen auftretende Magnetit-Ilmeniterze sind teilweise an intrusive, gabbroide Gesteine und teilweise an wahrscheinlich extrusive Amphibolite gebunden. Das TiO₂Fe-Verhältnis der Amphiboliterze beträgt 0,14–0,15 und ist innerhalb der einzelnen Vorkommen konstant. In den Gabbroerzen liegt das Verhältnis zwischen 0,21 und 0,35 und schwankt auch innerhalb der Einzelvorkommen stark.

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Magnetite-ilmenite ore in western Norway occurs partly in intrusive, gabbroic rocks, partly in amphibolites which seem to be extrusive. The relation TiO₂: Fe in the amphibolite ores is 0.14–0.15 and is constant within every deposit. In the gabbro ores the relation TiO₂Fe lies between 0.21 and 0.35 and varies also within every single deposit.

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Résumé Dans l'Ouest de la Norvège des gisements de magnétite-ilménite se trouvent en partie dans des roches gabbroïques et intrusives, en partie dans des amphibolites qui sont probablement extrusives. Le rapport TiO₂Fe dans les minerais amphibolitiques est de 0,14–0,15 et se montre très constant d'un gisement à l'autre. Dans les minerais gabbroïques, le rapport TiO₂Fe varie entre 0,21 et 0,35 et diffère selon le gisement.

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. TiO₂: Fe .

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Die Stellung der nordnorwegischen Eisenerzlagerstätte Andörja in der kaledonischen Geosynklinale     

Dr. Hans-Peter Geis 《International Journal of Earth Sciences》1967,56(1):561-567

Zusammenfassung Die Magnetiterzlager der Insel Andörja/Nordnorwegen liegen in einer Serie mesozonal metamorphisierter Sedimente des Kambro-Silurs der Kaledoniden: Granatglimmerschiefer Hangender Kalkmarmor (max. 5 Horizonte, die bis 9 m mächtig sind) Amphibolitschiefer (83–175 m mächtig, mit marin-sedimentären Magnetiterzen) Liegender Kalkmarmor (0–4 m mächtig) Granatglimmerschiefer, z. T. Quarzit.Diese Gesteinsfolge hat typisch miogeosynklinalen Charakter. Da sie westlich des Verbreitungsgebiets der eugeosynklinalen kaledonischen Sedimente und nahe dem Westrand des Verbreitungsgebiets kambro-silurischer Gesteine überhaupt auftritt, könnte es sich hier um den Westrand der Kaledoniden handeln. Westlich davon auftretende präkaledonische Gesteine könnten dann zur irischen Plattform gehören.

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The magnetite layers on the island of Andörja lie in a series of metamorphosed cambro-silurian sediments with the following sequence: garnet mica schist upper marble (max. 5 layers with up to 5 m thickness) amphibolite schist (83–175 m thickness, with marine sedimentary magnetite ore) lower marble (0–4 m thickness) garnet mica schist, partly quartzite.This rock sequence is of typically miogeosynclinal character. As it is situated to the west of the extension of the eugeosynclinal Caledonian rocks and near the western border of the cambro-silurian rocks on the whole, we might have here the western boundary of the caledonian geosyncline. Precaledonian rocks to the west of Andörja might then belong to the Irish platform.

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Résumé Les couches de magnétite du gisement d'Andörja se trouvent dans une série de sediments cambro-siluriens métamorphiques avec la séquence suivante: marbre supérieur (max. 5 horizons qui ont une épaisseur jusqu'à 9 m) amphibolite (83–175 m d'épaisseur, avec gisements de magnétite) marbre inférieur (0–4 m d'épaisseur) schistes de grenat et mica, en partie quartzites.La séquence est d'un caractère typiquement miogeosynclinal. Parce qu'elle apparaît à l'ouest de l'extension des roches eugéosynclinales calédoniennes et à la bordure des roches cambro-siluriennes en général, on y a probablement la frontière occidentale de la géosynclinale calédonienne. Les roches précalédoniennes plus à l'ouest pourraient alors appartenir à la plateforme d'Irlande.

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Andörja ( ), - : (9 ), (83–175 , ), (0–4 ), - , . . , .

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Effects of pollen leaching and microbial degradation on organic carbon and nutrient availability in lake water     

Stefan?R?sel  Anna?Rych?a  Christian?Wurzbacher  Hans-Peter?GrossartEmail author 《Aquatic Sciences - Research Across Boundaries》2012,74(1):87-99

Nutrient fluxes across terrestrial-aquatic boundaries and their subsequent integration into lake nutrient cycles are currently a major topic of aquatic research. Although pollen represents a good substrate for microorganisms, it has been neglected as a terrestrial source of organic matter in lakes. In laboratory experiments, we incubated pollen grains of Pinus sylvestris in water of lakes with different trophy and pH to estimate effects of pollen input and its subsequent microbial degradation on nutrient dynamics. In this ex situ experiment, we measured concentrations of organic carbon, phosphorus and nitrogen in the surrounding water as well as microbial dynamics (bacteria and fungal sporangia) at well-controlled conditions. Besides leaching, chemical and microbial decomposition of pollen was strongest within the first week of incubation. This led to a marked increase of soluble reactive phosphorus and total dissolved nitrogen (up to 0.04 and 1.5 mg L⁻¹, respectively, after 5 days of incubation) in the ambient water. In parallel, pollen grains were rapidly colonized by heterotrophic bacteria and aquatic fungi. Leaching and microbial degradation of pollen accounted for ≥80, ≥40, ≥50% for organic C, N and P, respectively, and did not significantly differ among water samples from the studied lakes. Thus, pollen introduces high amounts of bio-available terrestrial organic matter and nutrients into surface waters within a short time. A rough calculation on P input into oligotrophic Lake Stechlin indicates that pollen plays an important ecological role in nutrient cycling of temperate lakes. This requires further attention in aquatic ecology.  相似文献   

From drought to flood: A water balance analysis of the Tuolumne River basin during extreme conditions (2015–2017)     

Andrew R. Hedrick  Danny Marks  Hans-Peter Marshall  James McNamara  Scott Havens  Ernesto Trujillo  Micah Sandusky  Mark Robertson  Micah Johnson  Kat J. Bormann  Thomas H. Painter 《水文研究》2020,34(11):2560-2574

The degree to which the hydrologic water balance in a snow-dominated headwater catchment is affected by annual climate variations is difficult to quantify, primarily due to uncertainties in measuring precipitation inputs and evapotranspiration (ET) losses. Over a recent three-year period, the snowpack in California's Sierra Nevada fluctuated from the lightest in recorded history (2015) to historically heaviest (2017), with a relatively average year in between (2016). This large dynamic range in climatic conditions presents a unique opportunity to investigate correlations between annual water availability and runoff in a snow-dominated catchment. Here, we estimate ET using a water balance approach where the water inputs to the system are spatially constrained using a combination of remote sensing, physically based modelling, and in-situ observations. For all 3 years of this study, the NASA Airborne Snow Observatory (ASO) combined periodic high-resolution snow depths from airborne Lidar with snow density estimates from an energy and mass balance model to produce spatial estimates of snow water equivalent over the Tuolumne headwater catchment at 50-m resolution. Using observed reservoir inflow at the basin outlet and the well-quantified snowmelt model results that benefit from periodic ASO snow depth updates, we estimate annual ET, runoff efficiency (RE), and the associated uncertainty across these three dissimilar water years. Throughout the study period, estimated annual ET magnitudes remained steady (222 mm in 2015, 151 mm in 2016, and 299 mm in 2017) relative to the large differences in basin input precipitation (547 mm in 2015, 1,060 mm in 2016, and 2,211 mm in 2017). These values compare well with independent satellite-derived ET estimates and previously published studies in this basin. Results reveal that ET in the Tuolumne does not scale linearly with the amount of available water to the basin, and that RE primarily depends on total annual snowfall proportion of precipitation.  相似文献