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1.
A. van Geen K. Radloff Z. Aziz Z. Cheng M.R. Huq K.M. Ahmed B. Weinman S. Goodbred H.B. Jung Y. Zheng M. Berg P.T.K. Trang L. Charlet J. Metral D. Tisserand S. Guillot S. Chakraborty A.P. Gajurel B.N. Upreti 《Applied Geochemistry》2008
One of the reasons the processes resulting in As release to groundwater in southern Asia remain poorly understood is the high degree of spatial variability of physical and chemical properties in shallow aquifers. In an attempt to overcome this difficulty, a simple device that collects groundwater and sediment as a slurry from precisely the same interval was developed in Bangladesh. Recently published results from Bangladesh and India relying on the needle-sampler are augmented here with new data from 37 intervals of grey aquifer material of likely Holocene age in Vietnam and Nepal. A total of 145 samples of filtered groundwater ranging in depth from 3 to 36 m that were analyzed for As (1–1000 μg/L), Fe (0.01–40 mg/L), Mn (0.2–4 mg/L) and S (0.04–14 mg/L) are compared. The P-extractable (0.01–36 mg/kg) and HCl-extractable As (0.04–36 mg/kg) content of the particulate phase was determined in the same suite of samples, in addition to Fe(II)/Fe ratios (0.2–1.0) in the acid-leachable fraction of the particulate phase. Needle-sampler data from Bangladesh indicated a relationship between dissolved As in groundwater and P-extractable As in the particulate phase that was interpreted as an indication of adsorptive equilibrium, under sufficiently reducing conditions, across 3 orders of magnitude in concentrations according to a distribution coefficient of 4 mL/g. The more recent observations from India, Vietnam and Nepal show groundwater As concentrations that are often an order of magnitude lower at a given level of P-extractable As compared to Bangladesh, even if only the subset of particularly reducing intervals characterized by leachable Fe(II)/Fe >0.5 and dissolved Fe >0.2 mg/L are considered. Without attempting to explain why As appears to be particularly mobile in reducing aquifers of Bangladesh compared to the other regions, the consequences of increasing the distribution coefficient for As between the particulate and dissolved phase to 40 mL/g for the flushing of shallow aquifers of their initial As content are explored. 相似文献
2.
Pierre Strzerzynski Stéphane Guillot Gabriel Courrioux Patrick Ledru 《Comptes Rendus Geoscience》2005,337(14):1284-1292
The structural analysis and the 3D modelling of Stephanian granites of the Pelvoux Massif characterize an emplacement along sinistral NW–SE- and dextral NE–SW-trending shear zones in the Pelvoux and in the Aiguilles Rouges–Mont Blanc Massifs, respectively. This Carboniferous shear system is consistent with a north–south extension direction known in the whole Variscan belt at this time. To cite this article: P. Strzerzynski et al., C. R. Geoscience 337 (2005). 相似文献
3.
Mauricio González Guillot Mónica Escayola Rogelio Acevedo 《Journal of South American Earth Sciences》2011,31(1):1-16
The magmatic arc of the Fuegian Andes is composed mostly of Upper Mesozoic to Cenozoic calc-alkaline plutons and subordinated lavas. To the rear arc, however, isolated mid-Cretaceous monzonitic plutons and small calc-alkaline dykes and sills crop out. This calc-alkaline unit (the Ushuaia Peninsula Andesites, UPA) includes hornblende-rich, porphyritic quartz meladiorites, granodiorites, andesites, dacites and lamprophyres. Radiometric dating and cross-cutting relationships indicate that UPA is younger than the monzonitic suite. The geochemistry of UPA is medium to high K, with high LILE (Ba 500–2000 ppm, Sr 800–1400 ppm), HFSE (Th 7–23 ppm, Nb 7–13 ppm, Ta 0.5–1.1 ppm) and LREE (La 16–51 ppm) contents, along with relatively low HREE (Yb 1.7–1.3 ppm) and Y (9–19 ppm). The similar mineralogy and geochemistry of all UPA rocks suggest they evolved from a common parental magma, by low pressure crystal fractionation, without significant crustal assimilation. A pure Rayleigh fractionation model indicates that 60–65% of crystal fractionation of 60% hornblende + 34% plagioclase + 4% clinopyroxene + 1% Fe-Ti oxide, apatite and sphene (a paragenesis similar of UPA mafic rocks) can explain evolution from lamprophyres to dacites. The UPA has higher LILE, HFSE and LREE, and lower HREE and Y than the calc-alkaline plutons and lavas of the volcanic front. The HREE and Y are lower than in the potassic plutons as well. High concentrations of Th, Nb, Ta, Zr, Hf, LREE and Ce/Pb, and low U/Th, Ba/Th ratios in UPA, even in the least differentiated samples, suggest contributions from subducted sediments to the mantle source. On the other hand, relatively low HREE and Y, high LREE/HREE (La/Yb 11–38) ratios and Nb-Ta contents can be interpreted as mantle metasomatism by partial melts of either subducted garnetiferous oceanic sediment or basalt as well. Additionally, high LILE content in UPA, similar to the potassic plutons, suggests also a mantle wedge previously metasomatized by potassic parental magmas in their route to crustal levels. Therefore, UPA represents a unique suite in the Fuegian arc generated in a multiple hybridized source. UPA generation is related to a transition from normal to flat subduction which additionally caused the widening and landward migration of the magmatic arc, as well as crustal deformation. Rear-arc magmatism endured ca. 22 m.y.; afterwards, calc-alkaline magmatism remained at the volcanic front. 相似文献
4.
Burrows A Guillot T Hubbard WB Marley MS Saumon D Lunine JI Sudarsky D 《The Astrophysical journal》2000,534(1):L97-L100
The recent discovery that the close-in extrasolar giant planet HD 209458b transits its star has provided a first-of-its-kind measurement of the planet's radius and mass. In addition, there is a provocative detection of the light reflected off of the giant planet tau Bootis b. Including the effects of stellar irradiation, we estimate the general behavior of radius/age trajectories for such planets and interpret the large measured radii of HD 209458b and tau Boo b in that context. We find that HD 209458b must be a hydrogen-rich gas giant. Furthermore, the large radius of a close-in gas giant is not due to the thermal expansion of its atmosphere but to the high residual entropy that remains throughout its bulk by dint of its early proximity to a luminous primary. The large stellar flux does not inflate the planet but retards its otherwise inexorable contraction from a more extended configuration at birth. This implies either that such a planet was formed near its current orbital distance or that it migrated in from larger distances (>/=0.5 AU), no later than a few times 107 yr of birth. 相似文献
5.
Y. Agbossoumond R.-P. Mnot J.L. Paquette S. Guillot S. Yssoufou C. Perrache 《Gondwana Research》2007,12(4):476-488
The Palimé–Amlamé Pluton (PAP) in southern Togo, consists of silica-rich to intermediate granitoids including enclaves of mafic igneous rocks and of gneisses. They are commonly called the “anatectic complex of Palimé–Amlamé” and without any convincing data, they were interpreted either as synkinematic Pan-African granitoids or as reworked pre Pan-African plutons. New field and petrological observations, mineral and whole-rock chemical analyses together with U–Pb zircon dating, have been performed to evaluate the geodynamic significance of the PAP within the Pan-African orogenic belt. With regard to these new data, the granitoids and related enclaves probably result from mixing and mingling processes between mafic and silicic magmas from respectively mantle and lower crust sources. They display Mg–calc-alkaline chemical features and present some similarities with Late Archaean granites such as transitional (K-rich) TTGs and sanukitoids.
The 2127 ± 2 Ma age obtained from a precise U/Pb concordia on zircon, points out a Paleoproterozoic age for the magma crystallization and a lower intercept at 625 ± 29 Ma interpreted as rejuvenation during Pan-African tectonics and metamorphism. Based on these results, a Pan-African syn to late orogenic setting for the PAP, i.e. the so-called “anatectic complex of Palimé–Amlamé”, can be definitively ruled out. Moreover according to its location within the nappe pile and its relationships with the suture zone, the PAP probably represents a fragment of the West African Craton reactivated during the Pan-African collision. 相似文献
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7.
Philip J. Wallis Michael B. Ward Jamie Pittock Karen Hussey Howard Bamsey Amandine Denis Steven J. Kenway Carey W. King Shahbaz Mushtaq Monique L. Retamal Brian R. Spies 《Climatic change》2014,125(2):209-220
A variety of proposed activities to mitigate greenhouse gas emissions will impact on scarce water resources, which are coming under increasing pressure in many countries due to population growth and shifting weather patterns. However, the integrated analysis of water and carbon impacts has been given limited attention in greenhouse mitigation planning. In this Australian case study, we analyse a suite of 74 mitigation measures ranked as highest priority by one influential analysis, and we find that they have highly variable consequences for water quantity. We find: (1) The largest impacts result from land-based sequestration, which has the potential to intercept large quantities of water and reduce catchment yields, estimated to exceed 100 Mm3/MtCO2-e of carbon mitigated (100,000 l per tonne CO2-e). (2) Moderate impacts result from some renewable power options, including solar thermal power with a water cost estimated at nearly 4 Mm3/MtCO2-e. However, the water impacts of solar thermal power facilities could be reduced by designing them to use existing power-related water supplies or to use air or salt-water cooling. (3) Wind power, biogas, solar photovoltaics, energy efficiency and operational improvements to existing power sources can reduce water demand through offsetting the water used to cool thermal power generation, with minor savings estimated at 2 Mm3/MtCO2-e and amounting to nearly 100 Mm3 of water saved in Australia per annum in 2020. This integrated analysis significantly changes the attractiveness of some mitigation options, compared to the case where water impacts are not considered. 相似文献
8.
Marc?UlrichEmail author Manuel?Mu?oz Stéphane?Guillot Michel?Cathelineau Christian?Picard Benoit?Quesnel Philippe?Boulvais Clément?Couteau 《Contributions to Mineralogy and Petrology》2014,167(1):952
The weathering of mantle peridotite tectonically exposed to the atmosphere leads commonly to natural carbonation processes. Extensive cryptocrystalline magnesite veins and stock-work are widespread in the serpentinite sole of the New Caledonia ophiolite. Silica is systematically associated with magnesite. It is commonly admitted that Mg and Si are released during the laterization of overlying peridotites. Thus, the occurrence of these veins is generally attributed to a per descensum mechanism that involves the infiltration of meteoric waters enriched in dissolved atmospheric CO2. In this study, we investigate serpentinite carbonation processes, and related silicification, based on a detailed petrographic and crystal chemical study of serpentinites. The relationships between serpentine and alteration products are described using an original method for the analysis of micro-X-ray fluorescence images performed at the centimeter scale. Our investigations highlight a carbonation mechanism, together with precipitation of amorphous silica and sepiolite, based on a dissolution–precipitation process. In contrast with the per descensum Mg/Si-enrichment model that is mainly concentrated in rock fractures, dissolution–precipitation process is much more pervasive. Thus, although the texture of rocks remains relatively preserved, this process extends more widely into the rock and may represent a major part of total carbonation of the ophiolite. 相似文献
9.
The South Karakorum margin, east of the Himalayan syntaxis, consist of an E–W elongated zone of young (10–3 Ma) high‐grade metamorphic rocks (M2) and related migmatitic domes. This late tectono‐metamorphic event post‐dates the Palaeogene (55–37 Ma) phase of thickening of the belt featured by NW–SE structures and associated M1 amphibolite facies metamorphism (0.7 GPa, 700 °C). This M2 metamorphism is characterised by low‐pressure, high‐temperature conditions coeval with migmatite formation in response to a thermal increase of c. 150 °C compared to M1, culminating at a temperature of c. 770 °C and a pressure of 0.5–0.6 GPa. Rapid exhumation of migmatitic domes, at a rate of 5 mm yr?1, was accommodated by vertical extrusion, in the core of E–W crustal‐scale folds. These crustal‐scale folds formed in response to N–S syn‐collisional shortening and were enhanced by thermal weakening of the migmatised continental crust. M2 metamorphism is spatially and temporarily associated with granitoids showing a mantle affinity, firmly suggesting that this could be the advective heat source for the granite and syenite generation and the subsequent migmatisation of the mid‐crustal level. Such relationships between a mantle‐related magmatism and a high‐temperature metamorphism in a convergent shortening context are suggestive of the breakoff of the subducted Indian slab since 20 Ma. 相似文献
10.
In the last few years, deuterium has been the focus of a high level of laboratory activity that was sparked by a disagreement
on the experimental value of the maximum compression along the Hugoniot.
Astrophysically, the uncertainty in the EOS of hydrogen is most consequential in models of the interiors of Jupiter and Saturn
since a significant fraction of their mass falls in the region where the EOS uncertainty is largest. We present a study of
the range of interior structures allowed by the shock-compression experiments on deuterium and constrained by astrophysical
observations of the two planets. We find that the EOS uncertainty must be reduced to less than 3% along the planet’s isentrope
to get good interior models of Jupiter.
These models provide values for the mass of a core of heavy elements (other than H and He) and the total mass of heavy elements
in these planets. The amount and distribution of heavy elements are quite sensitive to the EOS of hydrogen and constitute
important clues to their formation process. 相似文献