U–Pb dating of the end of the Pan-African orogeny in the Tuareg shield: the post-collisional syn-shear Tioueine pluton (Western Hoggar, Algeria)     

J. L. Paquette  R. Caby  M. T. Djouadi  J. L. Bouchez 《Lithos》1998,45(1-4):245-253

The Tioueine pluton intrudes the Neoproterozoic series of the Iskel terrane, located in the Tuareg shield, western Hoggar. The consistency of the internal structures as well as the nature and organization of the associated microstructures demonstrate that the Tioueine pluton was emplaced syn-kinematically while N–S strike–slip shear zones were active. The syn-tectonic emplacement of the Tioueine massif implies that this pluton, although belatedly crystallized, entirely belongs to the concept of post-collisional magmatism. In order to date precisely the late Pan-African tectono-metamorphic event in the studied area, an U–Pb age of 523±1 Ma was obtained from abraded zircons of a late quartz–syenite from the Tioueine pluton. This early Cambrian age is younger than the other plutons of the Tuareg shield, which were mainly emplaced between 630 Ma and 580 Ma. This dating also shows that the Tuareg shield was not a single coherent block at 525 Ma, but rather an amalgam of active terranes moving each other along major shear zones. Finally, the Tioueine massif represents probably the final welding of the Tuareg shield assembly of terranes and consequently the end of the post-collisional orogenic episode in the whole Pan-African belt.  相似文献   

Combining IR and X‐ray microtomography data sets: Application to Itokawa particles and to Paris meteorite     

Zelia Dionnet  Rosario Brunetto  Alice Alon‐Toppani  Stefano Rubino  Donia Baklouti  Ferenc Borondics  Anne‐Ccile Buellet  Zahia Djouadi  Andrew King  Tomoki Nakamura  Alessandra Rotundi  Christophe Sandt  David Troadec  Akira Tsuchiyama 《Meteoritics & planetary science》2020,55(7):1645-1664

In the near future, a new generation of sample return missions (Hayabusa2, OSIRIS‐REx, MMX, etc.) will collect samples from small solar system bodies. To maximize the scientific outcome of laboratory studies and minimize the loss of precious extraterrestrial samples, an analytical sequence from less destructive to more destructive techniques needs to be established. In this work, we present a combined X‐ray and IR microtomography applied to five Itokawa particles and one fragment of the primitive carbonaceous chondrite Paris. We show that this analytical approach is able to provide a 3‐D physical and chemical characterization of individual extraterrestrial particles, using the measurement of their 3‐D structure and porosity, and the detection of mineral and organic phases, and their spatial co‐localization in 3‐D. We propose these techniques as an efficient first step in a multitechnique analytical sequence on microscopic samples collected by space missions.  相似文献   

Two refractory Wild 2 terminal particles from a carrot‐shaped track characterized combining MIR/FIR/Raman microspectroscopy and FE‐SEM/EDS analyses     

A. Rotundi  F. J. M. Rietmeijer  M. Ferrari  V. Della Corte  G. A. Baratta  R. Brunetto  E. Dartois  Z. Djouadi  S. Merouane  J. Borg  J. R. Brucato  L. Le Sergeant d'Hendecourt  V. Mennella  M. E. Palumbo  P. Palumbo 《Meteoritics & planetary science》2014,49(4):550-575

We present the analyses results of two bulk Terminal Particles, C2112,7,171,0,0 and C2112,9,171,0,0, derived from the Jupiter‐family comet 81P/Wild 2 returned by the Stardust mission. Each particle embedded in a slab of silica aerogel was pressed in a diamond cell. This preparation, as expected, made it difficult to identify the minerals and organic materials present in these particles. This problem was overcome using a combination of three different analytical techniques, viz. FE‐SEM/EDS, IR, and Raman microspectroscopy that allowed identifying the minerals and small amounts of amorphous carbon present in both particles. TP2 and TP3 were dominated by Ca‐free and low‐Ca, Mg‐rich, Mg,Fe‐olivine. The presence of melilite in both particles is supported by IR microspectroscopy, but is not confirmed by Raman microspectroscopy, possibly because the amounts are too small to be detected. TP2 and TP3 show similar silicate mineral compositions, but Ni‐free and low‐Ni, subsulfur (Fe,Ni)S grains are present in TP2 only. TP2 contains indigenous amorphous carbon hot spots; no indigenous carbon was identified in TP3. These nonchondritic particles probably originated in a differentiated body. This work found an unanticipated carbon contamination following the FE‐SEM/EDS analyses. It is suggested that organic materials in the embedding silica aerogel are irradiated during FE‐SEM/EDS analyses creating a carbon gas that develops a strong fluorescence continuum. The combination of the selected analytical techniques can be used to characterize bulk Wild 2 particles without the need of extraction and removal of the encapsulating aerogel. This approach offers a relatively fast sample preparation procedure, but compressing the samples can cause spurious artifacts, viz. silica contamination. Because of the combination of techniques, we account for these artifacts.  相似文献   

Mid-IR, Far-IR, Raman micro-spectroscopy, and FESEM-EDX study of IDP L2021C5: Clues to its origin     

R. Brunetto  J. Borg  F.J.M. Rietmeijer  C. Sandt  A. Rotundi  Z. Djouadi 《Icarus》2011,212(2):896-910

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VSP wavefield separation using the gray-scale Hough transform: synthetic data     

Asma Hadjadj  Zahia Benaissa  Abdelkader Benaissa  Amar Boudella 《Arabian Journal of Geosciences》2017,10(9):212

The principal objective in Vertical Seismic Profile (VSP) processing is the separation of the downgoing and upgoing wavefields. Several methods have been suggested in this area. This paper presents a new approach based on the gray-scale Hough transform (GSHT) which is an extension of the conventional Hough transform used to detect straight lines and other curves. The technique, we suggest here, directly maps the gray-scale VSP image, including the downgoing and upgoing linear events, in image coordinate space (x,t,g) to the gray Hough parameter counting space (θ,ρ,g), where θ and ρ are the polar parameters and g is the gray-scale value. In this new space, the downgoing events appear in the negative angles θ quadrant and the upgoing in the positive quadrant, owning to their opposite apparent velocities. The inverse GSHT algorithm, we developed in this study, is performed for extracting separately these two wavefields by considering the straight lines that satisfy the corresponding filtering conditions. The experimental results on synthetic VSP datasets are convincing. The wave separation is well performed, even in the presence of loud noise levels, with signal to noise ratio improvement and amplitude preservation, in contrast to median filtering.  相似文献   

Microstructural study of micron‐sized craters simulating Stardust impacts in aluminum 1100 targets     

Hugues Leroux  Janet Borg  David Troadec  Zahia Djouadi  Friedrich Hrz 《Meteoritics & planetary science》2006,41(2):181-196

Abstract— Various microscopic techniques were used to characterize experimental microcraters in aluminum foils to prepare for the comprehensive analysis of the cometary and interstellar particle impacts in aluminum foils to be returned by the Stardust mission. First, scanning electron microscopy (SEM) and energy dispersive X‐ray spectroscopy (EDS) were used to study the morphology of the impact craters and the bulk composition of the residues left by soda‐lime glass impactors. A more detailed structural and compositional study of impactor remnants was then performed using transmission electron microscopy (TEM), EDS, and electron diffraction methods. The TEM samples were prepared by focused ion beam (FIB) methods. This technique proved to be especially valuable in studying impact crater residues and impact crater morphology. Finally, we also showed that infrared microscopy (IR) can be a quick and reliable tool for such investigations. The combination of all of these tools enables a complete microscopic characterization of the craters.  相似文献   

Filtrage par reconnaissance des formes d’un profil sismique vertical Vertical seismic profile filtering through the use of pattern recognition     

Abdelkader Benaïssa  Zahia Benaïssa  Tahar Aïfa  Amar Boudella 《Swiss Journal of Geoscience》2009,102(2):297-306

To improve the signal to noise ratio of the vertical seismic profile recordings, we used a filtering method based on pattern recognition. It consists in recognizing along the seismic trace, corresponding to the arrivals of various events, the shape of the P wavelet considered as the training signal. This recognition is made of projections which retain only the signals similar in shape to the P wavelet, the others being attenuated according to their degree of resemblance to the training wavelet. The study undertaken on synthetic and real data shows that this method acts as an effective filter. However, it still depends on a training signal that must be well defined and identifiable.  相似文献   

Comparative Life Cycle Assessment of Two Types of Truck Bumper Produced in the Algerian Auto Industry     

KEBBOUCHE Zahia  TAIRI Abdelaziz  SAFI Brahim 《资源与生态学报(英文版)》2020,11(4):378-387

Currently, the reduction of weight in automotive is a very important topic to reduce the air pollution. In this context, the purpose of the present paper is to analyze a real case study through a comparison of the environmental impacts between a conventional steel bumper and a polyester prototype. In the first part of this work, a door-to-door life-cycle assessment methodology was used throughout the study of the component manufacturing phase. The SimaPro 7.1 software is used to evaluate the impacts of both bumpers on the environment and health. The second part is devoted to dust analysis from the polyester workshop. The obtained results have allowed us to show the company that its choice of steel substitution by the polyester is advantageous for certain impacts including the impact of climate change, but unfortunately there may be, given the working conditions of the polyester workshop, a transfer of impact, since we will end up with a risk of health (irritations, cancers) for the workers. LCA has proven to be a very useful tool for validating a redesigned automotive component from an environmental point of view; from this case study, several recommendations were made for the company to design environmentally friendly components, and ecodesign should be introduced into the company’s procedures.  相似文献   

Visible‐IR and Raman microspectroscopic investigation of three Itokawa particles collected by Hayabusa: Mineralogy and degree of space weathering based on nondestructive analyses          下载免费PDF全文

L. Bonal  R. Brunetto  P. Beck  E. Dartois  Z. Dionnet  Z. Djouadi  J. Duprat  E. Füri  Y. Kakazu  G. Montagnac  P. Oudayer  E. Quirico  C. Engrand 《Meteoritics & planetary science》2015,50(9):1562-1576

Hayabusa‐returned samples offer a unique perspective for understanding the link between asteroids and cosmomaterials available in the laboratory, and provide insights on the early stages of surface space weathering. This study characterizes the mineralogy and the extent of space weathering of the three Itokawa particles RA‐QD02‐0163, RA‐QD02‐0174, and RA‐QD02‐0213 provided by JAXA to our consortium. We report here a series of results based on nondestructive analyses through visible‐near‐infrared reflectance and Raman spectroscopy. Results were obtained on the raw particles, both in their original containers and deposited on diamond windows. Identification of the minerals, characterization of their elemental compositions, and measurements of their relative abundances were led through Raman spectroscopy in punctual and automatic mode. Reflectance spectra in the visible and near‐IR wavelengths constrain the mineralogy of the grains and allow direct comparison with the surface of Itokawa. The spectra reflect the extent of space weathering experienced by the three particles. Particle RA‐QD02‐0163 consists of a heterogeneous mixture of minerals: olivine (Fo₇₆) dominates an assemblage with both Ca‐rich (En₅₀, Wo₅₀) and Ca‐poor (En₈₅) pyroxenes. The elemental compositions of the silicates are consistent with those previously reported for distinct Hayabusa particles. Particles RA‐QD‐0174 and RA‐QD02‐0213 are solely composed of olivine, whose chemical composition is similar to that observed in RA‐QD02‐0163. It has been previously shown that the S‐type asteroid 25143 Itokawa is a breccia of poorly equilibrated LL4 and highly equilibrated LL5 and LL6 materials. The three particles studied here can be related to the least metamorphosed lithology (LL4) based on the high forsterite content of the olivine. Neither carbonaceous matter nor hydrated minerals were detected through Raman on the three allocated particles. The NIR‐VIS reflectance (incidence = 45°, light collection at e = 0°) spectra of the three particles, in particular the 1 μm band, are consistent with the presence of both olivine and pyroxene detected via Raman. The spectra of particles RA‐QD02‐0163 and RA‐QD02‐0213 are also fully compatible with the ground‐based observations of asteroid (25143) Itokawa in terms of both spectral features and slope. By contrast, particle RA‐QD02‐0174 has a similar 1 μm band depth but higher (redder) spectral slope than the surface of Itokawa. This probably reveals a variable extent of space weathering among the regolith particles. RA‐QD02‐0174 may contain a higher amount of nanophase metallic iron and nanophase FeS. Such phases are products by space weathering induced by solar wind, previously detected on other Itokawa particles.  相似文献