Compressibility of Ca3Al2Si3O12 perovskite up to 55 GPa     

Steeve Gréaux  Denis Andrault  Laurent Gautron  Nathalie Bolfan-Casanova  Mohamed Mezouar 《Physics and Chemistry of Minerals》2014,41(6):419-429

Compressibility of perovskite-structured Ca₃Al₂Si₃O₁₂ grossular (GrPv) was investigated at high pressure and high temperature by means of angle-dispersive powder X-ray diffraction using a laser-heated diamond anvil cell. We observed the Pbnm orthorhombic distortion for the pure phase above 50 GPa, whereas below this pressure, Al-bearing CaSiO₃ perovskite coexists with an excess of corundum. GrPv has a bulk modulus (K ₀ = 229 ± 5 GPa; \(K_{0}^{{\prime }}\) fixed to 4) almost similar to that reported for pure CaSiO₃ perovskite. Its unit-cell volume extrapolated to ambient conditions (V ₀ = 187.1 ± 0.4 Å³) is found to be ~2.5 % larger than for the Al-free phase. We observe an increasing unit-cell anisotropy with increasing pressure, which could have implications for the shear properties of Ca-bearing perovskite in cold slabs subducted into the Earth’s mantle.  相似文献   

Review of solutions for 3D hydrodynamic modeling applied to aquaculture in South Pacific atoll lagoons   总被引：1，自引：0，他引：1  

Andréfouët S  Ouillon S  Brinkman R  Falter J  Douillet P  Wolk F  Smith R  Garen P  Martinez E  Laurent V  Lo C  Remoissenet G  Scourzic B  Gilbert A  Deleersnijder E  Steinberg C  Choukroun S  Buestel D 《Marine pollution bulletin》2006,52(10):1138-1155

A workshop organized in French Polynesia in November 2004 allowed reviewing the current methods to model the three-dimensional hydrodynamic circulation in semi-enclosed atoll lagoons for aquaculture applications. Mollusk (e.g. pearl oyster, clam) aquaculture is a major source of income for South Pacific countries such as French Polynesia or Cook Islands. This aquaculture now requires a better understanding of circulation patterns to improve the spatial use of the lagoons, especially to define the best area to set larvae collectors. The pelagic larval duration of the relevant species (<20 days) and the size of the semi-closed lagoons (few hundreds of km2) drive the specifications of the model in terms of the spatial and temporal scale. It is considered that, in contrast with fish, mollusk larvae movements are limited and that their cycle occurs completely in the lagoon, without an oceanic stage. Atolls where aquaculture is productive are generally well-bounded, or semi-closed, without significant large and deep openings to the ocean. Nevertheless part of the lagoon circulation is driven by oceanic water inputs through the rim, ocean swells, tides and winds. Therefore, boundary conditions of the lagoon system are defined by the spatial structure of a very shallow rim (exposition and number of hoas), the deep ocean swell climate, tides and wind regimes. To obtain a realistic 3D numerical model of lagoon circulation with adequate forcing, it is thus necessary to connect in an interdisciplinary way a variety of methods (models, remote sensing and in situ data collection) to accurately represent the different components of the lagoon system and its specific boundary conditions. We review here the current methods and tools used to address these different components for a hypothetical atoll of the Tuamotu Archipelago (French Polynesia), representative of the semi-closed lagoons of the South Pacific Ocean. We hope this paper will serve as a guide for similar studies elsewhere and we provide guidelines in terms of costs for all the different stages involved.  相似文献   

Analysis of the effect of trees on block propagation using a DEM model: implications for rockfall modelling     

David Toe  Franck Bourrier  Ignacio Olmedo  Jean-Matthieu Monnet  Frédéric Berger 《Landslides》2017,14(5):1603-1614

The objective of this research was to use numerical models based on mechanical approaches to improve the integration of the protective role of forests against rockfall into block propagation models. A model based on the discrete element method (DEM) was developed to take into account the complex mechanical processes involved during the impact of a block on a tree. This modelling approach requires the definition of many input parameters and cannot be directly integrated into block propagation models. A global sensitivity analysis identified the leading parameters of the block kinematics after impact (i.e. block energy reduction, trajectory changes, and rotational velocity): the impact velocity, the tree diameter, and the impact point horizontal location (i.e. eccentricity). Comparisons with the previous experimental and numerical studies of block impacts on trees demonstrated the applicability of the DEM model and showed some of the limitations of earlier approaches. Our sensitivity analysis highlights the significant influence of the impact velocity on the reduction of the block’s kinetic energy. Previous approaches usually also focus on parameters such as impact height, impact vertical incidence, and tree species, whose importance is only minor according to the present results. This suggests that the integration of forest effects into block propagation models could be both improved and simplified. The DEM model can also be used as an alternative to classical approaches for the integration of forest effects by directly coupling it with block propagation models. This direct coupling only requires the additional definition of the location and the diameter of each tree. Indeed, the input parameters related to the mechanical properties of the stem and the block/stem interaction in the DEM model can be set to average values because they are not leading parameters. The other input parameters are already defined or calculated in the block propagation model.  相似文献   

Determination of the Tin Stable Isotopic Composition in Tin‐bearing Metals and Minerals by MC‐ICP‐MS          下载免费PDF全文

Gerhard Brügmann  Daniel Berger  Ernst Pernicka 《Geostandards and Geoanalytical Research》2017,41(3):437-448

This study uses MC‐ICP‐MS for the precise analysis of the stable tin isotopic composition in ore minerals of tin (cassiterite, stannite), tin metal and tin bronze. The ultimate goal is to determine the provenance of tin in ancient metal objects. We document the isotope compositions of reference materials and compare the precision of different isotope ratios and the accuracy of different procedures of mass fractionation correction. These data represent a base with which isotopic data of future studies can be directly compared. The isotopic composition of cassiterite and stannite can be determined after reduction to tin metal and bronze, respectively. Both metals readily dissolve in HCl, but while the solutions of tin metal can be directly measured, the bronze solutions must be purified with an anion exchanger. The correction of the mass bias is best performed with an internal Sb standard and an empirical regression method. A series of Sn isotope determinations on commercially available mono‐element Sn solutions as well as reference bronze materials and tin minerals show fractionations ranging from about ?0.09‰ to 0.05‰/amu. The combined analytical uncertainty (2s) was determined by replicate dissolutions of reference materials of bronze (BAM 211, IARM‐91D) and averages at about 0.005‰/amu.  相似文献   

Suspended particulate matter and vertical fluxes of sedimentary material in bays of the Murmansk (Barents Sea) and Karelian (White Sea) coasts     

M.?V.?MityaevEmail author  M.?V.?Gerasimova  V.?Ja.?Berger 《Oceanology》2017,57(2):306-314

Synchronous measurement of the total suspended organic and mineral particulate matter, together with vertical sedimentary matter flux, carried out in various areas of Yarnyschnaya Inlet (Murmansk coast of the Barents Sea) and Chupa Inlet (Karelian coast of the White Sea) revealed that the seston organic component plays no part in sedimentation, being almost completely utilized in the water column, while the majority of mineral matter is transported out of the bay. The total amount of suspended matter and its components in the water column is estimated, as well as the total flux of sedimentary matter to the bottom of Chupa and Yarnyschnaya inlets.  相似文献   

The origin of banding in the Main Donegal Granite,N.W. Ireland     

A. R. Berger 《Geological Journal》1971,7(2):347-358

This Caledonian pluton exhibits a regular, sub-vertical banding in which layers of dark, relatively fine grained trondhjemite alternate with layers of light, coarse grained granite. The textures and the presence of cross-cutting bands of granite indicate that the light bands were derived by potash feldspathization of the trondhjemite. The geometry of the banding indicates that it formed during the “synplutonic” deformation of the pluton, largely in situ. The bands formed by segregation of alkalies into dilatant zones of movement produced during the deformation of partly consolidated magma.  相似文献