Elemental composition of individual chondrules from carbonaceous chondrites,including Allende     

T.W Osborn  R.G Warren  R.H Smith  H Wakita  D.L Zellmer  R.A Schmitt 《Geochimica et cosmochimica acta》1974,38(9):1359-1378

Major and trace element analyses of over 180 individual chondrules from 12 carbonaceous chondrites are reported, including individual analyses of 60 chondrules from Pueblito de Allende. Siderophile elements in most chondrules are depleted, compared to the whole chondrite. Correlations of Al-Ir and Ir-Sc among chondrules high in Ca and Al were observed. A Cu-Mn correlation was also found for chondrules from some meteorites. No correlation was observed between Au and other siderophile elements (Fe, Ni, Co and Ir). It is suggested that these elemental associations were present in the material from which the chondrules formed. Compositionally, chondrules appear to be a multicomponent mixture of remelted dust. One component displaying an Al-Ir correlation is identified as Allende-type white aggregates. The other components are a material chemically similar to the present matrix and sulfides-plus-metal material. Abundances of the REE (rare earth elements) were measured in ‘ordinary’ Allende chondrules and were 50% higher than REE abundances in Mokoia chondrules; REE abundances in Ca-Al rich chondrules were similar to REE abundances in Ca-rich white aggregates.  相似文献   

Evidence for MTBE in Heating Oil     

Gary A. Robbins  Brent J. Henebry  Barbara M. Schmitt  Frank B. Bartolomeo  Aaron Green  Peter Zack 《Ground Water Monitoring & Remediation》1999,19(2):65-69

"Contamination of heating oil with MTBE could result in increasing the environmental impact of subsurface heating oil releases."  相似文献   

Provenance discrimination of fine sediments by mid-infrared spectroscopy: Calibration and application to fluvial palaeo-environmental reconstruction     

Stoil Chapkanski  Damien Ertlen  Claire Rambeau  Laurent Schmitt 《Sedimentology》2020,67(2):1114-1134

Determining sediment provenance allows a better understanding of fluvial palaeo-dynamics, and identifying involved watersheds, at broad spatio-temporal scales. Conventional approaches for source identification are usually based on the physical, mineralogical, geochemical, magnetic or isotopic properties of sediments. Rapid, non-destructive and, in well-established contexts, highly accurate, mid-infrared spectroscopy is an alternative method for investigating sediment sources. The present research objectives are: (i) to use the mid-infrared spectroscopy method to discriminate the provenance of fine sediments, by applying discriminant analysis on a large set of reference samples from three different watersheds in the Upper Rhine area (associated with the Rhine, Ill and Vosges tributaries); (ii) to clarify whether the provenance spectra signatures are influenced by riverine depositional contexts (bars versus banks) and, to some extent, by grain size and/or high organic matter content; and (iii) to apply the mid-infrared spectroscopy – discriminant analysis method to a study of fluvial palaeo-dynamics and determine the provenance of palaeo-channel infillings. Three main sedimentary sources, divided into eight sub-categories, have been characterized by 196 modern reference samples from 78 collecting sites. Discriminant analysis displayed a strong separating power by classifying correctly the origin of samples without any inter-group overlap, independently from the geomorphological context (bar or bank) and associated slight changes in organic matter contents or grain size. Mid-infrared spectroscopy – discriminant analysis investigations of the palaeo-channel infill, complemented by radiocarbon dates and mineralogical data, allowed reconstructing general trends for the local morpho-sedimentary dynamics over the last ca 12 millennia.  相似文献   

Determination of Radiogenic 87Sr/86Sr and Stable δ88/86SrSRM987 Isotope Values of Thirteen Mineral,Vegetal and Animal Reference Materials by DS‐TIMS     

Jean‐Michel Brazier  Anne‐Dsire Schmitt  Eric Pelt  Damien Lemarchand  Sophie Gangloff  Tho Tacail  Vincent Balter 《Geostandards and Geoanalytical Research》2020,44(2):331-348

This work presents new ⁸⁷Sr/⁸⁶Sr and δ^88/86Sr_SRM987 isotopic values of thirteen mineral, vegetal and animal reference materials. Except for UB‐N, all our results are consistent with previously published data. Our results highlight intermediate precisions among the best presently published and a non‐significant systematic shift with the calculated δ^88/86Sr_SRM987 mean values for the three most analysed reference materials in the literature (i.e., IAPSO, BCR‐2 and JCp‐1). By comparison with the literature and between two distinct digestions, a significant bias of δ^88/86Sr_SRM987 values was highlighted for two reference materials (UB‐N and GS‐N). It has also been shown that digestion protocols (nitric and multi‐acid) have a moderate impact on the δ^88/86Sr_SRM987 isotopic values for the Jls‐1 reference materials suggesting that a nitric acid digestion of carbonate can be used without significant bias from partial digestion of non‐carbonate impurities. Different δ^88/86Sr_SRM987 values were measured after two independent Sr/matrix separations, according to the same protocol, for a fat‐rich organic reference material (BCR‐380R) and have been related to a potential post‐digestion heterogeneity. Finally, the δ^88/86Sr_SRM987 value differences measured between animal‐vegetal and between coral‐seawater reference materials agree with the previously published results, highlighting an Sr isotopic fractionation along the trophic chain and during carbonate precipitation.  相似文献   

Numerical Modeling of Ice Fog in Interior Alaska Using the Weather Research and Forecasting Model     

Chang Ki Kim  Martin Stuefer  Carl G. Schmitt  Andrew Heymsfield  Greg Thompson 《Pure and Applied Geophysics》2014,171(8):1963-1982

An ice microphysics parameterization scheme has been modified to better describe and understand ice fog formation. The modeling effort is based on observations in the Sub-Arctic Region of Interior Alaska, where ice fog occurs frequently during the cold season due to abundant water vapor sources and strong inversions existing near the surface at extremely low air temperatures. The microphysical characteristics of ice fog are different from those of other ice clouds, implying that the microphysical processes of ice should be changed in order to generate ice fog particles. Ice fog microphysical characteristics were derived with the NCAR Video Ice Particle Sampler during strong ice fog cases in the vicinity of Fairbanks, Alaska, in January and February 2012. To improve the prediction of ice fog in the Weather Research and Forecasting model, observational data were used to change particle size distribution properties and gravitational settling rates, as well as to implement a homogeneous freezing process. The newly implemented homogeneous freezing process compliments the existing heterogeneous freezing scheme and generates a higher number concentration of ice crystals than the original Thompson scheme. The size distribution of ice crystals is changed into a Gamma distribution with the shape factor of 2.0, using the observed size distribution. Furthermore, gravitational settling rates are reduced for the ice crystals since the crystals in ice fog do not precipitate in a similar manner when compared to the ice crystals of cirrus clouds. The slow terminal velocity plays a role in increasing the time scale for the ice crystals to settle to the surface. Sensitivity tests contribute to understanding the effects of water vapor emissions as an anthropogenic source on the formation of ice fog.  相似文献   

A kinematic model of vertical geomagnetic field variation resulting from a steady convective flow     

Alexandra Marsenić 《地球物理与天体物理流体动力学》2014,108(2):191-212

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The Lemnos 8 January 2013 (M w = 5.7) earthquake: fault slip,aftershock properties and static stress transfer modeling in the north Aegean Sea     

Athanassios Ganas  Zafeiria Roumelioti  Vassilios Karastathis  Konstantinos Chousianitis  Alexandra Moshou  Evangelos Mouzakiotis 《Journal of Seismology》2014,18(3):433-455

We investigate mainshock slip distribution and aftershock activity of the 8 January 2013 M _w?=?5.7 Lemnos earthquake, north Aegean Sea. We analyse the seismic waveforms to better understand the spatio-temporal characteristics of earthquake rupture within the seismogenic layer of the crust. Peak slip values range from 50 to 64 cm and mean slip values range from 10 to 12 cm. The slip patches of the event extend over an area of dimensions 16?×?16 km². We also relocate aftershock catalog locations to image seismic fault dimensions and test earthquake transfer models. The relocated events allowed us to identify the active faults in this area of the north Aegean Sea by locating two, NE–SW linear patterns of aftershocks. The aftershock distribution of the mainshock event clearly reveals a NE–SW striking fault about 40 km offshore Lemnos Island that extends from 2 km up to a depth of 14 km. After the mainshock most of the seismic activity migrated to the east and to the north of the hypocenter due to (a) rupture directivity towards the NE and (b) Coulomb stress transfer. A stress inversion analysis based on 14 focal mechanisms of aftershocks showed that the maximum horizontal stress is compressional at N84°E. The static stress transfer analysis for all post-1943 major events in the North Aegean shows no evidence for triggering of the 2013 event. We suggest that the 2013 event occurred due to tectonic loading of the North Aegean crust.  相似文献   

Erratum to: The Lemnos 8 January 2013 (M w=5.7) earthquake: fault slip,aftershock properties and static stress transfer modeling in the north Aegean Sea     

Athanassios Ganas  Zafeiria Roumelioti  Vassilios Karastathis  Konstantinos Chousianitis  Alexandra Moshou  Evangelos Mouzakiotis 《Journal of Seismology》2015,19(1):273-273

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Influence of a position of the critical level inside a plane layer on the rise of magnetically and thermally driven instabilities     

Alexandra Marsenić  Sebastián Ševčík 《地球物理与天体物理流体动力学》2013,107(5):457-476

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Middle Eocene‐Oligocene broken‐foreland evolution in the Andean Calchaqui Valley,NW Argentina: insights from stratigraphic,structural and provenance studies     

C. del Papa  F. Hongn  J. Powell  P. Payrola  M. Do Campo  M. R. Strecker  I. Petrinovic  A. K. Schmitt  R. Pereyra 《Basin Research》2013,25(5):574-593

Two end‐member models have been proposed for the Paleogene Andean foreland: a simple W‐E migrating foreland model and a broken‐foreland model. We present new stratigraphic, sedimentological and structural data from the Paleogene Quebrada de los Colorados (QLC) Formation, in the Eastern Cordillera, with which to test these two different models. Basin‐wide unconformities, growthstrata and changes in provenance indicate deposition of the QLC Formation in a tectonically active basin. Both west‐ and east‐vergent structures, rooted in the basement, controlled the deposition and distribution of the QLC Formation from the Middle Eocene to the Early Miocene. The provenance analysis indicates that the main source areas were basement blocks, like the Paleozoic Oire Eruptive Complex, uplifted during Paleogene shortening, and that delimits the eastern boundary of the present‐day intraorogenic Puna plateau. A comparison of the QLC sedimentary basin‐fill pattern with those of adjacent Paleogene basins in the Puna plateau and in the Santa Bárbara System highlights the presence of discrete depozones. These reflect the early compartmentalization of the foreland, rather than a stepwise advance of the deformation front of a thrust belt. The early Tertiary foreland of the southern central Andes is represented by a ca. 250‐km‐wide area comprising several deformation zones (Arizaro, Macón, Copalayo and Calchaquí) in which doubly vergent or asymmetric structures, rooted in the basement, were generated. Hence, classical foreland model is difficult to apply in this Paleogene basin; and our data and interpretation agree with a broken‐foreland model.  相似文献