The formation conditions of enstatite chondrites: Insights from trace element geochemistry of olivine‐bearing chondrules in Sahara 97096 (EH3)          下载免费PDF全文

Emmanuel Jacquet  Olivier Alard  Matthieu Gounelle 《Meteoritics & planetary science》2015,50(9):1624-1642

We report in situ LA‐ICP‐MS trace element analyses of silicate phases in olivine‐bearing chondrules in the Sahara 97096 (EH3) enstatite chondrite. Most olivine and enstatite present rare earth element (REE) patterns comparable to their counterparts in type I chondrules in ordinary chondrites. They thus likely share a similar igneous origin, likely under similar redox conditions. The mesostasis however frequently shows negative Eu and/or Yb (and more rarely Sm) anomalies, evidently out of equilibrium with olivine and enstatite. We suggest that this reflects crystallization of oldhamite during a sulfidation event, already inferred by others, during which the mesostasis was molten, where the complementary positive Eu and Yb anomalies exhibited by oldhamite would have possibly arisen due to a divalent state of these elements. Much of this igneous oldhamite would have been expelled from the chondrules, presumably by inertial acceleration or surface tension effects, and would have contributed to the high abundance of opaque nodules found outside them in EH chondrites. In two chondrules, olivine and enstatite exhibit negatively sloped REE patterns, which may be an extreme manifestation of a general phenomenon (possibly linked to near‐liquidus partitioning) underlying the overabundance of light REE observed in most chondrule silicates relative to equilibrium predictions. The silicate phases in one of these two chondrules show complementary Eu, Yb, and Sm anomalies providing direct evidence for the postulated occurrence of the divalent state for these elements at some stage in the formation reservoir of enstatite chondrites. Our work supports the idea that the peculiarities of enstatite chondrites may not require a condensation sequence at high C/O ratios as has long been believed.  相似文献   

Genesis of the Jurassic Carbonate‐Hosted Pb–Zn Deposits of Jebel Ressas (North‐Eastern Tunisia): Evidence from Mineralogy,Petrography and Trace Metal Contents and Isotope (O,C, S,Pb) Geochemistry     

Nejib JEMMALI  Fouad SOUISSI  Torsten W. VENNEMANN  Emmanuel John M. CARRANZA 《Resource Geology》2011,61(4):367-383

The Jebel Ressas Pb–Zn deposits in North‐Eastern Tunisia occur mainly as open‐space fillings (lodes, tectonic breccia cements) in bioclastic limestones of the Upper Jurassic Ressas Formation and along the contact of this formation with Triassic rocks. The galena–sphalerite association and their alteration products (cerussite, hemimorphite, hydrozincite) are set within a calcite gangue. The Triassic rocks exhibit enrichments in trace metals, namely Pb, Co and Cd enrichment in clays and Pb, Zn, Cd, Co and Cr enrichment in carbonates, suggesting that the Triassic rocks have interacted with the ore‐bearing fluids associated with the Jebel Ressas Pb–Zn deposits. The δ¹⁸O content of calcite associated with the Pb–Zn mineralization suggests that it is likely to have precipitated from a fluid that was in equilibrium with the Triassic dolostones. The δ³⁴S values in galenas from the Pb–Zn deposits range from ?1.5 to +11.4‰, with an average of 5.9‰ and standard deviation of 3.9‰. These data imply mixing of thermochemically‐reduced heavy sulfur carried in geothermal‐ and fault‐stress‐driven deep‐seated source fluid with bacterially‐reduced light sulfur carried in topography‐driven meteoric fluid. Lead isotope ratios in galenas from the Pb–Zn deposits are homogenous and indicate a single upper crustal source of base‐metals for these deposits. Synthesis of the geochemical data with geological data suggests that the base‐metal mineralization at Jebel Ressas was formed during the Serravallian–Tortonian (or Middle–Late Miocene) Alpine compressional tectonics.  相似文献   

Application of the principal component analysis on geochemical data: a case study in the basement complex of Southern Ilesa area, Nigeria     

Emmanuel A. Ariyibi  Samuel L. Folami  Bankole D. Ako  Taye R. Ajayi  Adebowale O. Adelusi 《Arabian Journal of Geosciences》2011,4(1-2):239-247

The study area occupies a part in southern Ilesa and is located within the schist belt of southwestern Nigeria, which embraces undifferentiated schist, gneisses, and migmatites with pegmatites, schist and epidorite complex, quartzite and quartz schist, granite gneiss, amphibolite, pegmatised schist, granulite, and gneiss. The study is aimed at clarifying the potential source of mineralization dealt with before in regional studies. Sixty-one soil samples were collected and analyzed for identifying these elements: Pb, Fe, Ni, Cd, Cr, Cu, Zn, and Mn. Multivariate analysis was done to obtain the coefficients of principal components from the standardized variables The elemental associations from the principal components analysis that accounted for 85.34% variability of the total variance are: Fe–Mn, Pb–Cr, and Cd–Zn. Comparably, these are equivalent with the previous results in the amphibolites and added the extension of association region to involve the schist and epidorite complex, quartzite, and quartz schist. The metallic association ratio revealed high metallic concentrations and led to the mineralization trend in southern Ilesa.  相似文献   

The future of three‐dimensional microscopic imaging in marine biology     

Renaud Boistel  Jim Swoger  Uroš Kržič  Vincent Fernandez  Brigitte Gillet  Emmanuel G. Reynaud 《Marine Ecology》2011,32(4):438-452

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Titan's 3-micron spectral region from ISO high-resolution spectroscopy     

Athena Coustenis  Alberto Negrão  Alberto Salama  Emmanuel Lellouch  Pierre Drossart  Bernard Schmitt  Andrei Nikitin 《Icarus》2006,180(1):176-185

The near-infrared spectrum of Titan, Saturn's largest moon and one of the Cassini/Huygens' space mission primary targets, covers the 0.8 to 5 micron region in which it shows several weak CH₄ absorption regions, and in particular one centered near 2.75 micron. Due to the interference of telluric absorption, only part of this window region (2.9-3.1 μm) has previously been observed from the ground [Noll, K.S., Geballe, T.R., Knacke, R., Pendleton, F., Yvonne, J., 1996. Icarus 124, 625-631; Griffith, C.A., Owen, T., Miller, G.A., Geballe, T., 1998. Nature 395, 575-578; Griffith, C.A., Owen, T., Geballe, T.R., Rayner, J., Rannou, P., 2003. Science 300, 628-630; Geballe, T.R., Kim, S.J., Noll, K.S., Griffith, C.A., 2003. Astrophys. J. 583, L39-L42]. We report here on the first spectroscopic observations of Titan covering the whole 2.4-4.9 μm region by two instruments on board the Infrared Space Observatory (ISO) in 1997. These observations show the 2.75-μm window in its complete extent for the first time. In this study we have also used a high-resolution Titan spectrum in the 2.9-3.6 μm region taken with the Keck [Geballe, T.R., Kim, S.J., Noll, K.S., Griffith, C.A., 2003. Astrophys. J. 583, L39-L42; Kim, S.J., Geballe, T.R., Noll, K.S., Courtin, R., 2005. Icarus 173, 522-532] to infer information on the atmospheric parameters (haze extinction, single scattering albedo, methane abundance, etc.) by fitting the methane bands with a detailed microphysical model of Titan's atmosphere (updated from Rannou, P., McKay, C.P., Lorenz, R.D., 2003. Planet. Space Sci. 51, 963-976). We have included in this study an updated version of a database for the CH₄ absorption coefficients [STDS, Wenger, Ch., Champion, J.-P., 1998. J. Quant. Spectrosc. Radiat. Transfer 59, 471-480. See also http://www.u-bourgogne.fr/LPUB/TSM/sTDS.html for latest updates; Boudon, V., Champion, J.-P., Gabard, T., Loëte, M., Michelot, F., Pierre, G., Rotger, M., Wenger, Ch., Rey, M., 2004. J. Mol. Spectrosc. 228, 620-634]. For the atmosphere we find that (a) the haze extinction profile that best matches the data is one with higher (by 40%) extinction in the atmosphere with respect to Rannou et al. (2003) down to about 30 km where a complete cut-off occurs; (b) the methane mixing ratio at Titan's surface cannot exceed 3% on a disk-average basis, yielding a maximum CH₄ column abundance of 2.27 km-am in Titan's atmosphere. From the derived surface albedo spectrum in the 2.7-3.08 micron region, we bring some constraints on Titan's surface composition. The albedo in the center of the methane window varies from 0.01 to 0.08. These values, compared to others reported in the other methane windows, show a strong compatibility with the water ice spectrum in the near-infrared. Without confirming its existence from this work alone, our data then appear to be compatible with water ice. A variety of other ices, such as CO₂, NH₃, tholin material or hydrocarbon liquid cannot be excluded from our data, but an additional unidentified component with a signature around 2.74 micron is required to satisfy the data.  相似文献   

Experimental analysis of groundwater flow through a landslide slip surface using natural and artificial water chemical tracers     

Stephane Binet  Herve Jomard  Thomas Lebourg  Yves Guglielmi  Emmanuel Tric  Catherine Bertrand  Jacques Mudry 《水文研究》2007,21(25):3463-3472

Artificial and natural tracer tests combined with high accurate electronic distancemeter measurements are conducted on a small landslide with a well known slip surface geometry. Outflow yields and chemical contents are monitored for all the experiment duration and they analyzed to estimate the slip surface hydraulic parameters. The main result is that the slip surface acts as a drain for groundwater flows that evacuates interstitial pressures in the slope and brings the sliding mass to be more stable one. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Outer bulge and in-plane bar of the milky way     

Sébastien Picaud  Emmanuel Chereul  Annie C. Robin  Francisco Garzón 《Astrophysics and Space Science》2003,284(2):523-526

We present the results of two studies of the inner Galaxy : on the one hand, a maximum likelihood fitting method using the Besançon model of Galaxy to constrain the density laws of the outer bulge and the holed disc; on the other hand, the comparison of Besançon simulations with infrared data on fields near longitude 20–27 degrees to verify the existence of a long and thin in-plane bar. These two parallel studies seem to show the co-existence of a structure (the bar) in addition with a very oblate outer bulge.  相似文献   

Split Comet C/2001 A2 (LINEAR)     

Jehin  Emmanuel  Boehnhardt  Hermann  Sekanina  Zdenek  Bonfils  Xavier  Schütz  Oliver  Beuzit  Jean-Luc  Billeres  Malvina  Garradd  Gordon J.  Leisy  Pierre  Marchis  Franck  Más  Antonio  Origlia  Livia  Scarpa  Daniel  Thomas  Daniel  Tozzi  Gian Paolo 《Earth, Moon, and Planets》2002,90(1-4):147-151

Comet C/2001 A2 experienced several splitting events duringits 2001 perihelion passage. The first break-upevent was observed in March 2001 (IAUC 7616).In this paper we report the first results of ourextensive imaging and spectroscopic monitoring campaignwith ESO telescopes over several weeks before andafter the perihelion passage on May 25 2001.  相似文献   

Mineral Prospectivity Mapping based on Isolation Forest and Random Forest: Implication for the Existence of Spatial Signature of Mineralization in Outliers     

Zhang  Shuai  Carranza  Emmanuel John M.  Xiao  Keyan  Wei  Hantao  Yang  Fan  Chen  Zhenghui  Li  Nan  Xiang  Jie 《Natural Resources Research》2022,31(4):1981-1999

Natural Resources Research - Known mineralized locations and randomly chosen non-mineralized locations are used traditionally as training samples in data-driven mineral prospectivity mapping (MPM)....  相似文献   

NRR Changes: Editorial     

Emmanuel John M. Carranza 《Natural Resources Research》2014,23(1):1-2

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