Plasma Jet Experiments Using LULI 2000 Laser Facility

We present experiments performed with the LULI2000 nanosecond laser facility. We generated plasma jets by using specific designed target. The main measured quantities related to the jet such as its propagation velocity, temperature and emissive radius evolution are presented. We also performed analytical work, which explains the jet evolution in some cases.     

阿尔金断裂晚新生代左旋走滑位错的地质新证据

通过对沿阿尔金断裂中段 (位于东经 88°至 92°)发育的晚第三纪走滑盆地沉积历史和走滑变形过程的野外观测以及对第四纪索尔库里盆地形成和演化过程的沉积环境复原的分析 ,提出了阿尔金断裂中段晚新生代左旋走滑位错的地质新证据。研究表明 ,晚第三纪走滑盆地经历了中新世晚期至上新世早期斜张走滑拉分和上新世晚期以来左旋错动的演化过程 ,沉积体沿断裂的错位分布特征指示至少发生了 80 km的左旋走滑位错。发育于阿尔金山链内部的索尔库里盆地起源于晚第三纪早期强烈的侵蚀作用 ,成为柴达木盆地快速沉积的主要物源区。该侵蚀盆地于中晚更新世闭合并演化成一个独立的沉积盆地。通过侵蚀盆地外流通道的复原指示阿尔金断裂自晚第三纪以来累积了 80～ 1 0 0 km的左旋位错。在此基础上 ,结合穿越断裂构造的 级区域水系形成的洪积裙宽度和主干河道沿断裂迹线的拐折长度 ,探讨了阿尔金断裂晚新生代左旋走滑位错量沿走向分布的特征 ,估算了左旋走滑速率     

Geochemistry of Karroo dolerite sills in the Calvinia district,Western Cape Province,South Africa

Two Karroo dolerite sills display chemical and mineralogical variation compatible with cumulus enrichment. The Blaauwkrans sill is an olivine tholeiite and contains a central zone slightly enriched in olivine, plagioclase and clinopyroxene. The thicker Hangnest sill is a quartz tholeiite and shows evidence of crystal settling and has a lower zone enriched in cumulus orthopyroxene and plagioclase.The two sills differ quite markedly in their trace element compositions, with the Hangnest magma enriched by a factor of two in LIL elements (Rb, Ba, Nb, Zr, Y) relative to the Blaauwkrans magma. The Hangnest magma contained extremely low Ni contents (3–5 ppm), whereas the Blaauwkrans magma contained higher but more normal Ni (100–110ppm). Such contrasting trace element compositions preclude any simple genetic relationship between the two Karroo magmas but they may be related either through a common parent or are derivatives from separate parental magmas.South African Contribution No. 24 to the International Geodynamics Project     

Infiltration von Flusswasser in Dünengebieten

Ohne Zusammenfassung     

Spinel lherzolite xenoliths from the Premier kimberlite (Kaapvaal craton, South Africa): Nature and evolution of the shallow upper mantle beneath the Bushveld complex

Coarse-grained, granular spinel lherzolites xenoliths from the Premier kimberlite show evidence of melt extraction and metasomatic enrichment, documenting a complex history for the shallow mantle beneath the Bushveld complex. Compositions of orthopyroxene, clinopyroxene and spinel indicate equilibration within the spinel–peridotite facies of the upper mantle, at depths from 80 to 100 km and temperatures from 720 to 850 °C. Bulk compositions have lower Mg-number [atomic 100 Mg/(Mg + Fe*)] than previously studied spinel peridotites from Premier, and have higher Mg/Si than low-temperature coarse grained garnet lherzolites, suggesting shallower melting conditions or metasomatic enrichment. Clinopyroxene in one sample is highly LREE-depleted indicating very minor modification of a residue of 20% melt extraction, whereas the calculated REE pattern for a melt in equilibrium with a mildly LREE-depleted sample is similar to MORB or late Archean basalt, possibly related to the Bushveld Complex. Bulk and mineral compositions suggest minimal refertilization by silicate melts in four out of six samples, but REE patterns indicate introduction of a LIL-enriched component that may be related to kimberlite.     

Spécificités hydrogéologiques des hautes vallées alpines: Exemple de la Haute-Sarine (Suisse)

The alpine valley of the Haute-Sarine is on several accounts representative of the alluvial aquifers of mountain by its very environment and its hydrogeologic characteristics. The investigations and the analysis carried out within the framework of this study enabled us to improve knowledge on the Quaternary filling of the valley and to highlight the preferential supplies of the aquifer by infiltration of the river and precipitations and also by the underground contributions of evaporitic karsts. We also could note the opulence of groundwater resources of the Haute-Sarine both from the qualitative and the quantitative points of view. The knowledge of these typical characteristics of alluvial aquifers of high altitude allowed finally the development of a concept of management and protection of groundwater resources that falls under a sustainable development policy of the groundwater storage in the alpine areas. Manuscrit re?u le 4 février 2003 Révision acceptée le 30 mars 2005     

Optimization with the Gradual Deformation Method

Building reservoir models consistent with production data and prior geological knowledge is usually carried out through the minimization of an objective function. Such optimization problems are nonlinear and may be difficult to solve because they tend to be ill-posed and to involve many parameters. The gradual deformation technique was introduced recently to simplify these problems. Its main feature is the preservation of the spatial structure: perturbed realizations exhibit the same spatial variability as the starting ones. It is shown that optimizations based on gradual deformation converge exponentially to the global minimum, at least for linear problems. In addition, it appears that combining the gradual deformation parameterization with optimizations may remove step by step the structure preservation capability of the gradual deformation method. This bias is negligible when deformation is restricted to a few realization chains, but grows increasingly when the chain number tends to infinity. As in practice, optimization of reservoir models is limited to a small number of iterations with respect to the number of gridblocks, the spatial variability is preserved. Last, the optimization processes are implemented on the basis of the Levenberg–Marquardt method. Although the objective functions, written in terms of Gaussian white noises, are reduced to the data mismatch term, the conditional realization space can be properly sampled.     

Water organisation at the solid–aqueous solution interfaceOrganisation de l'eau à l'interface solide–solution aqueuse

The aim of this review is to examine the present knowledge about water structure close to an interface or confined in porous spaces. First, the structure of liquid water is briefly described. Though its understanding remains incomplete, it appears that it is largely dominated by the hydrogen bond network and its dynamical evolution. The presence of any ‘foreign’ substance in water perturbs such a structure by changing at least locally the hydrogen bond network. For this reason, the presence of a solid interface significantly modifies the structure of the first adsorbed layers. Whatever the support, it is now clearly evidenced that structural perturbations are limited to distances lower than 10–15 Å from the interface. The nature, energetic heterogeneity and hydrophilicility/hydrophobicity of the solid surface influence the arrangement of water molecules. This surface organisation must definitely be considered when studying adsorption phenomena at the solid–aqueous solution interface. The relevance of such problems to geosciences is illustrated by a few situations in which water structure plays a prominent role. To cite this article: L.J. Michot et al., C. R. Geoscience 334 (2002) 611–631.     

Directional wave spectra at the regional scale with the KuROS airborne radar: comparisons with models

Ocean Dynamics - In situ observations, satellite observations, and regional observations from airborne remote sensing are very useful to characterize sea state evolution and related physical...