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1.
Samuel Ebert Addi Bischoff Dennis Harries Sarah Lentfort Jean‐Alix Barrat Andreas Pack Jrme Gattacceca Robbin Visser Peter Schmid‐Beurmann Stephan Kimpel 《Meteoritics & planetary science》2019,54(2):328-356
Based on the high abundance of fine‐grained material and its dark appearance, NWA 11024 was recognized as a CM chondrite, which is also confirmed by oxygen isotope measurements. But contrary to known CM chondrites, the typical phases indicating aqueous alteration (e.g., phyllosilicates, carbonates) are missing. Using multiple analytical techniques, this study reveals the differences and similarities to known CM chondrites and will discuss the possibility that NWA 11024 is the first type 3 CM chondrite. During the investigation, two texturally apparent tochilinite–cronstedtite intergrowths were identified within two thin sections. However, the former phyllosilicates were recrystallized to Fe‐rich olivine during a heating event without changing the textural appearance. A peak temperature of 400–600 °C is estimated, which is not high enough to destroy or recrystallize calcite grains. Thus, calcites were never constituents of the mineral paragenesis. Another remarkable feature of NWA 11024 is the occurrence of unknown clot‐like inclusions (UCLIs) within fine‐grained rims, which are unique in this clarity. Their density and S concentration are significantly higher than of the surrounding fine‐grained rim and UCLIs can be seen as primary objects that were not formed by secondary alteration processes inside the rims. Similarities to chondritic and cometary interplanetary dust particles suggest an ice‐rich first‐generation planetesimal for their origin. In the earliest evolution, NWA 11024 experienced the lowest degree of aqueous alteration of all known CM chondrites and subsequently, a heating event dehydrated the sample. We suggest to classify the meteorite NWA 11024 as the first type 3 CM chondrite similar to the classification of CV3 chondrites (like Allende) that could also have lost their matrix phyllosilicates by thermal dehydration. 相似文献
2.
Alix Lombard Anny Cazenave Pierre Yves Le Traon Stephanie Guinehut Cécile Cabanes 《Ocean Dynamics》2006,56(5-6):445-451
In this paper, we first discuss the controversial result of the work by Cabanes et al. (Science 294:840–842, 2001), who suggested that the rate of past century sea level rise may have been overestimated, considering the limited and heterogeneous
location of historical tide gauges and the high regional variability of thermal expansion which was supposed to dominate the
observed sea level. If correct, this conclusion would have solved the problem raised by the IPCC third assessment report [Church
et al, Cambridge University Press, Cambridge, pp 881, 2001], namely, the factor two difference between the 20th century observed sea level rise and the computed climatic contributions.
However, recent investigations based on new ocean temperature data sets indicate that thermal expansion only explains part
(about 0.4 mm/year) of the 1.8 mm/year observed sea level rise of the past few decades. In fact, the Cabanes et al.’s conclusion
was incorrect due to a contamination of abnormally high ocean temperature data in the Gulf Stream area that led to an overestimate
of thermal expansion in this region. In this paper, we also estimate thermal expansion over the last decade (1993–2003), using
a new ocean temperature and salinity database. We compare our result with three other estimates, two being based on global
gridded data sets, and one based on an approach similar to that developed here. It is found that the mean rate of thermosteric
sea level rise over the past decade is 1.5±0.3 mm/year, i.e. 50% of the observed 3 mm/year by satellite altimetry. For both
time spans, past few decades and last decade, a contribution of 1.4 mm/year is not explained by thermal expansion, thus needs
to be of water mass origin. Direct estimates of land ice melt for the recent years account for about 1 mm/year sea level rise.
Thus, at least for the last decade, we have moved closer to explaining the observed rate of sea level rise than the IPCC third
assessment report. 相似文献
3.
Klaus KEIL Timothy J. McCOY Lionel WILSON Jean‐Alix BARRAT Doug RUMBLE Matthias M. M. MEIER Rainer WIELER Gary R. HUSS 《Meteoritics & planetary science》2011,46(11):1719-1741
Abstract– We studied the mineralogy, petrology, and bulk, trace element, oxygen, and noble gas isotopic compositions of a composite clast approximately 20 mm in diameter discovered in the Larkman Nunatak (LAR) 04316 aubrite regolith breccia. The clast consists of two lithologies: One is a quench‐textured intergrowth of troilite with spottily zoned metallic Fe,Ni which forms a dendritic or cellular structure. The approximately 30 μm spacings between the Fe,Ni arms yield an estimated cooling rate of this lithology of approximately 25–30 °C s?1. The other is a quench‐textured enstatite‐forsterite‐diopside‐glass vitrophyre lithology. The composition of the clast suggests that it formed at an exceptionally high degree of partial melting, perhaps approaching complete melting, and that the melts from which the composite clast crystallized were quenched from a temperature of approximately 1380–1400 °C at a rate of approximately 25–30 °C s?1. The association of the two lithologies in a composite clast allows, for the first time, an estimation of the cooling rate of a silicate vitrophyre in an aubrite of approximately 25–30 °C s?1. While we cannot completely rule out an impact origin of the clast, we present what we consider is very strong evidence that this composite clast is one of the elusive pyroclasts produced during pyroclastic volcanism on the aubrite parent body ( Wilson and Keil 1991 ). We further suggest that this clast was not ejected into space but retained on the aubrite parent body by virtue of the relatively large size of the clast of approximately 20 mm. Our modeling, taking into account the size of the clast, suggests that the aubrite parent body must have been between approximately 40 and 100 km in diameter, and that the melt from which the clast crystallized must have contained an estimated maximum range of allowed volatile mass fractions between approximately 500 and approximately 4500 ppm. 相似文献
4.
Determination of Rare Earth Elements, Sc, Y, Zr, Ba, Hf and Th in Geological Samples by ICP-MS after Tm Addition and Alkaline Fusion 总被引：2，自引：0，他引：2
Germain Bayon Jean Alix Barrat Joël Etoubleau Mathieu Benoit Claire Bollinger Sidonie Révillon 《Geostandards and Geoanalytical Research》2009,33(1):51-62
We present a revised method for the determination of concentrations of rare earth (REE) and other trace elements (Y, Sc, Zr, Ba, Hf, Th) in geological samples. Our analytical procedure involves sample digestion using alkaline fusion (NaOH-Na2 O2 ) after addition of a Tm spike, co-precipitation on iron hydroxides, and measurement by sector field-inductively coupled plasma-mass spectrometry (SF-ICP-MS). The procedure was tested successfully for various rock types (i.e., basalt, ultramafic rock, sediment, soil, granite), including rocks with low trace element abundances (sub ng g−1 ). Results obtained for a series of nine geological reference materials (BIR-1, BCR-2, UB-N, JP-1, AC-E, MA-N, MAG-1, GSMS-2, GSS-4) are in reasonable agreement with published working values. 相似文献
5.
A global eddy-admitting ocean/sea-ice simulation driven over 1958–2004 by daily atmospheric forcing is used to evaluate spatial
patterns of sea level change between 1993 and 2001. In the present study, no data assimilation is performed. The model is
based on the Nucleus for European Models of the Ocean code at the 1/4° resolution, and the simulation was performed without
data assimilation by the DRAKKAR project. We show that this simulation correctly reproduces the observed regional sea level
trend patterns computed using satellite altimetry data over 1993–2001. Generally, we find that regional sea level change is
best simulated in the tropical band and northern oceans, whereas the Southern Ocean is poorly simulated. We examine the respective
contributions of steric and bottom pressure changes to the total regional sea level changes. For the steric component, we
analyze separately the contributions of temperature and salinity changes as well as upper and lower ocean contributions. Generally,
the model results show that most regional sea level changes arise from temperature changes in the upper 750 m of the ocean.
However, contributions of salinity changes and deep steric changes can be locally important. We also propose a map of ocean
bottom pressure changes. Finally, we assess the robustness of such a model by comparing this simulation with a second simulation
performed by MERCATOR-Ocean based on the same core model, but differing by its short length of integration (1992–2001) and
its surface forcing data set. The long simulation presents better performance over 1993–2001 than the short simulation, especially
in the Southern Ocean where a long adjustment time seems to be needed.
In memory of my little brother Jean-Eudes, whose thirst for science filled out the rich discussions we had about my investigations
and his job as user-service provider for MERCATOR-Ocean. 相似文献
6.
Toulier Alix Lachassagne Patrick Hendrayana Heru Fadillah Arif Jourde Hervé 《Hydrogeology Journal》2023,31(3):849-851
Hydrogeology Journal - 相似文献
7.
8.
Germain Bayon Dominique Birot Claire Bollinger Jean Alix Barrat 《Geostandards and Geoanalytical Research》2011,35(1):145-153
We report on an improved method for determining trace element abundances in seawater and other natural waters. The analytical procedure involves co‐precipitation on iron hydroxides after addition of a Tm spike, and measurement by inductively coupled plasma‐sector field mass spectrometry (ICP‐SFMS). The validity of the method was assessed through a series of co‐precipitation experiments, using ultra‐diluted solutions of a certified rock reference material (BIR‐1). Results obtained for four natural water reference materials (NASS‐5, CASS‐4, SLEW‐3, SLRS‐4) are in agreement with published working values for rare earth elements, yttrium, vanadium and, when available, for hafnium, zirconium, thorium and scandium. A set of proposed values with uncertainties typically better than 8% RSD is proposed for Hf, Zr and Th. 相似文献
9.
10.
Matthew Coggon Caryl Ann Becerra Klaus Nüsslein Karen Miller Richard Yuretich Sarina J. Ergas 《Geochimica et cosmochimica acta》2012
Biological reduction of iron-sulfate minerals, such as jarosite, has the potential to contribute to the natural attenuation of acid mine drainage (AMD) sites. Previous studies of AMD attenuation at Davis Mine, an abandoned pyrite mine in Rowe Massachusetts, provided evidence of iron and sulfate reduction by indigenous bacteria. Jarosite is a large component of the sediment at Davis Mine and may play a role in AMD attenuation. In this study, microcosms were constructed with groundwater and sediment from Davis Mine and amended with glycerol, nitrogen and phosphorus (GNP) and naturally formed natrojarosite. Over time, higher total iron, sulfate, pH and sodium concentrations and lower oxidation–reduction potentials were observed in microcosms amended with GNP and jarosite, compared with unamended microcosms and killed controls. Geochemical modeling predicted jarosite precipitation under microcosm conditions, suggesting that abiotic processes were unlikely contributors to jarosite dissolution. SEM imaging at the jarosite surface showed microbial attachment. Microbial community composition analysis revealed a shift to higher populations of Clostridia, which are known to reduce both iron and sulfate. The results show that jarosite may be utilized as an electron acceptor by iron and/or sulfate reducing bacteria at Davis Mine and its presence may aid in the attenuation of AMD. 相似文献