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101.
Electron paramagnetic resonance of Ir2+ in forsterite is studied at Q-band frequency and room temperature. There are four equivalent spectra superimposed along the three crystallographic axes. The individual spectrum consists of four hyperfine lines of approximately equal intensity separated from each other by 42 G; one axis of the g tensor is near the c axis. Ir2+ is certainly substituted for Mg2+. Because of the fourfold degeneracy of the EPR spectrum, it may be suggested that iridium occurs at M1. Taking into account that one eigenvector of the g tensor is nearly parallel to c, it seems also possible that the substitution takes place at the M2 position. In this case, the lattice relaxation of the crystal structure around Ir2+ at M2 must break the point symmetry m at M2. 相似文献
102.
Jean-Marie Auzende Mathilde Cannat Pascal Gente Jean-Pierre Henriet Thierry Juteau Jeffrey Karson Yves Lagabrielle Catherine Mével Maurice Tivey 《地学学报》1994,6(2):143-148
The objective of the 20 Nautile dives of the recent Kanaut cruise was to study the southern wall of the Kane Fracture Zone from its eastern intersection with the Mid-Atlantic Ridge (MAR) to 5 Myr in age. The geological mapping shows four successive massifs, wrench faulted and slightly tilted. The transform-facing walls of these massifs exhibit outcrops of fresh and serpentinized peridotites, gabbros and basalts. The entire crustal exposure is cataclased and metamorphosed to greenschist facies. 相似文献
103.
Lepoint G Vangeluwe D Eisinger M Paster M van Treeck P Bouquegneau JM Gobert S 《Marine pollution bulletin》2004,48(5-6):465-470
A (15)N tracer study was performed during an experimental transplantation trial of natural Posidonia oceanica cuttings. The experiment was done in situ at 17 m depth in the Revellata Bay (Calvi, NW Corsica, France). Despite high survival rates of transplants (>90%) after one year, the weight and the N content of transplants are significantly lower than those of reference plants. In absence of roots, the transplants are not able to meet their N requirement, because leaf uptake is insufficient to replenish the N lost during the natural leaf decay. This could constitute a major cause of long-term failure for transplantation experiments or natural re-colonisation processes. The increase of the (15)N content in the roots shows that the plant re-allocates the nitrogen of one organ (i.e. leaves, rhizomes) to ensure the growth of another (i.e. roots). 相似文献
104.
Gaye Bayrakci Carla Scalabrin Stéphanie Dupré Isabelle Leblond Jean-Baptiste Tary Nadine Lanteri Jean-Marie Augustin Laurent Berger Estelle Cros André Ogor Christos Tsabaris Marc Lescanne Louis Géli 《Marine Geophysical Researches》2014,35(3):211-229
A rotating, acoustic gas bubble detector, BOB (Bubble OBservatory) module was deployed during two surveys, conducted in 2009 and 2011 respectively, to study the temporal variations of gas emissions from the Marmara seafloor, along the North Anatolian Fault zone. The echosounder mounted on the instrument insonifies an angular sector of 7° during a given duration (of about 1 h). Then it rotates to the next, near-by angular sector and so forth. When the full angular domain is insonified, the “pan and tilt system” rotates back to its initial position, in order to start a new cycle (of about 1 day). The acoustic data reveal that gas emission is not a steady process, with observed temporal variations ranging between a few minutes and 24 h (from one cycle to the other). Echo-integration and inversion performed on the acoustic data as described in the companion paper of Leblond et al. (Mar Geophys Res, 2014), also indicate important variations in, respectively, the target strength and the volumetric flow rates of individual sources. However, the observed temporal variations may not be related to the properties of the gas source only, but reflect possible variations in sea-bottom currents, which could deviate the bubble train towards the neighboring sector. During the 2011 survey, a 4-component ocean bottom seismometer (OBS) was co-located at the seafloor, 59 m away from the BOB module. The acoustic data from our rotating, monitoring system support, but do not provide undisputable evidence to confirm, the hypothesis formulated by Tary et al. (2012), that the short-duration, non-seismic micro-events recorded by the OBS are likely produced by gas-related processes within the near seabed sediments. Hence, the use of a multibeam echosounder, or of several split beam echosounders should be preferred to rotating systems, for future experiments. 相似文献
105.
Martine Mullet Sophie BoursiquotMustapha Abdelmoula Jean-Marie GéninJean-Jacques Ehrhardt 《Geochimica et cosmochimica acta》2002,66(5):829-836
Tetragonal FeS1−x mackinawite, has been synthesized by reacting metallic iron with a sodium sulfide solution and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), transmission Mössbauer spectroscopy (TMS) and X-ray photoelectron spectroscopy (XPS). Based on XRD and TEM analyses, synthetic mackinawite exhibits crystallization and is identical to the natural mineral. Unit cell parameters derived from XRD data are a = b = 0.3670 nm and c = 0.5049 nm. The bulk Fe:S ratio derived from the quantitative dispersive energy analysis is practically 1. XPS analyses, however, showed that mackinawite surface is composed of both Fe(II) and Fe(III) species bound to monosulfide. Accordingly, monosulfide is the dominant S species observed at the surface with lesser amount of polysulfides and elemental sulfur. TMS analysis revealed the presence of both Fe(II) and Fe(III) in the mackinawite structure, thus supporting the XPS analysis. We propose that the iron monosulfide phase synthesized by reacting metallic iron and dissolved sulfide is composed of Fe(II) and S(-II) atoms with the presence of a weathered thin layer covering the bulk material that consists of both Fe(II) and Fe(III) bound to S(-II) atoms and in a less extent of polysulfide and elemental sulfur. 相似文献