Parallele entre la géochimie des schistes paléozoiques et celle des formations granitiques dans le Massif du Lys-Caillaouas (Pyrénées centrales)

The granitic “Lys-Caillaouas” Massive outcrops on 50 km² in the paleozoic series of the axial zone, situated in the North West of the Maladetta. It is known for its apparent stratified formations, emphasized by pelitic (Northern and French part of the Massive) and calcareous (Southern and Spanish part) enclaves. Its “emplacement” by syncinematic intrusion of a “granite magma” was formerly postulated with reference to the then wide-spread theory of magmas and “magmatical phases” of orogeneses. However care had not been taken to examine if this scheme would take into account the particular features of this Massive as they appear through a detailed study. Starting from entirely different points of view, the authors do not think it permissible, as a method of thinking, to consider a priori the granite as extraneous to the formations in which it crops out. For this reason, starting with the mainly structural observations of M.Clin (1959), which were completed by recent mapping done by a geological group of Nancy, they have undertaken in the “Lys-Caillaouas” massive and in its vicinity, a comparative geochemical study of the paleozoic basement of the axial zone and of the igneous formations therein enclosed. These different igneous facies, from porphyroblastic granites to quartz diorite, countain enclaves, some of them mainly pelitic and others calcareous. Besides these facies are arranged in sequences and in folded structures well related to those of the paleozoic host formation. These two facts clearly show:

• -the sedimentary origin of the most apparent differenciations of the igneous complex.
• -the “keeping in place“ of sedimentary horizons during the granitization which is an observed fact and not a hypothesis as is the case with the “emplacement” of granites.

     

Ultraviolet Laser Sampling and High Resolution Inductively Coupled Plasma-Mass Spectrometry of NIST and BCR-2G Glass Reference Materials

A Merchantek LUV266 ^TM petrographic ultraviolet (UV) laser microprobe has been used in conjunction with a Finnigan MAT ELEMENT ^TM high resolution ICP double-focusing mass spectrometer (HR-ICP-MS) for solid microsampling and geochemical analysis. This new configuration for laser ablation has the advantage of coupling the high sensitivity and fast scanning technology applied in the ELEMENT with the ablation efficiency of a UV laser. Optimisation of the configuration on the synthetic NIST SRM 612 glass standard reference material using Q-switched UV laser energy of 2 mJ and a 5 Hz repetition rate demonstrates: (1) a linear element response factor throughout the mass spectrum, suggesting limited fractionation during laser ablation; (2) a high sensitivity and very low background noise for most elements of interest; (3) limits of detection ranging from 3 ng g-1 for Sc to 300 pg g-1 for U; (4) a flat topped peak shape suitable for precise isotopic measurements; and (5) a flat bottomed crater geometry which permits progressive ablation for the analysis of thin sections. Average precision and accuracy estimates based on replicate analyses of synthetic NIST standard reference material and USGS BCR-2G glasses are below 10% for most elements.     

Unprecedented risk of spring frost damage in Switzerland and Germany in 2017

Spring frosts are feared by farmers, fruit growers, and wine growers as they can cause significant damage to crops when they occur during the development of the plants. In the second half of April 2017, following a very warm period that had caused premature vegetation growth, a cold air mass from the Arctic penetrated central and western Europe, causing severe damage to natural and cultivated vegetation over broad areas. Here, we analyze how exceptional this event was in Switzerland and Germany in relation to the accumulated growing degree days (GDD), used as a proxy for plant phenology advancement. Although this damaging frost was not the latest on record in terms of calendar days, our results show that it was, in some regions, unprecedented in relation to the accumulated warmth during the preceding period, at least since the beginning of instrumental temperature records (1864). Our results also highlight how global warming has considerably increased the number of days with mean temperature above 5 °C in late winter and early spring, especially since 1970 (+?16.8?±?4.7 °C days decade^?1). However, in spite of earlier spring phenology due to climate warming, our results suggest that the risk of damaging frost events to vegetation has remained unchanged over the last 150 years in lowlands of Switzerland and Germany, due to the concurring earlier occurrence of the last potentially damaging frosts (about ??20 days since 1864). Our analyses reveal therefore that the April 2017 damaging frost was a true outlier in terms of risk of frost damage to plants.     

Long-term variability of the Be/X-ray binary A 0535+26 – I. Optical and UV spectroscopy

The results of a 7-yr optical and UV spectroscopic study of the high-mass X-ray binary A 0535+26 are presented. It was found that throughout the period of the observations the line profile of Hα showed considerable variability. A correlation between the equivalent width of Hα and both V -band magnitude and ( B − V ) colour excess was observed, albeit with considerable scatter present in the data set. A giant X-ray flare in early 1994 was accompanied by a fading in optical and infrared photometric bands, and a reduction in the equivalent width of Hα. When the star was observed in 1994 September, it was found to have developed a double-peaked Hα profile, and further observations saw the V/R peak ratio vary cyclically, with a period of ∼1 yr. If this is identified as a global one-armed oscillation, it becomes the shortest period ever observed in a Be star. The accompanying photometric and spectroscopic observations provide a test of any theory seeking to describe the onset and behaviour of such a density wave.     

北秦岭造山带翠华山黑云母花岗岩LA-ICP-MS锆石U-Pb测年及地球化学特征

秦岭翠华山水湫池地区分布的黑云母花岗岩是陕西翠华山国家山崩地质公园的崩塌母岩,目前还未见对其系统地开展年代学、地球化学研究。本文在野外调查的基础上,对翠华山水湫池地区分布的黑云母花岗岩首次进行了LA-ICP-MS锆石U-Pb测年、Lu-Hf同位素及全岩地球化学分析,获得锆石U-Pb加权平均年龄为149.4Ma±1.1 Ma,时代属于晚侏罗世;结合前人的研究成果资料,翠华山复式岩体可能存在～227 Ma、～150 Ma、～119 Ma三期岩浆侵位活动;全岩地球化学分析具有高硅(w(SiO₂)=69.83%～75.31%)、富钾(w(K₂O)=2.71%～5.23%)、弱过铝质(A/CNK=1.00～1.07)特征,属于高钾钙碱性-钾玄岩Ⅰ型花岗岩;其轻、重稀土分馏明显(w(LREE)/w(HREE)=10.09～67.50),富集LILE(K、La、Pb、Sr)、亏损HFSE(Ta、Nb、P、Ti),Eu呈弱负异常—轻微正异常,且显示高Sr低Y花岗岩特征;锆石Hf同位素分析得出ε_Hf(t)=-4.6～-1.4,T_...     

Nested gridding and streamline-based simulation for fast reservoir performance prediction

Detailed reservoir models routinely contain 10⁶–10⁸ grid blocks. These models often cannot be used directly in a reservoir simulation because of the time and memory required for solving the pressure grid on the fine grid. We propose a nested gridding technique that efficiently obtains an approximate solution for the pressure field. The domain is divided into a series of coarse blocks, each containing several fine cells. Effective mobilities are computed for each coarse grid block and the pressure is then found on the coarse scale. The pressure field within each coarse block is computed using flux boundary conditions obtained from the coarse pressure solution. Streamline-based simulation is used to move saturations forward in time. We test the method for a series of example waterflood problems and demonstrate that the method can give accurate estimates of oil production for large 3D models significantly faster than direct simulation using streamlines on the fine grid, making the method overall approximately up to 1,000 times faster than direct conventional simulation.