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TL;DR: In this paper, X-ray absorption near-edge structure (XANES) spectroscopy at both Ca and Al K-edges has been used to investigate the environment of Al and Ca in peralkaline glasses obtained, by classic quenching methods, in the CaO-Al2O3-SiO2 (CAS) system and in calcium aluminate glasses obtained by ultra-quench from laser heating.
126 citations
TL;DR: It is shown that the observed Nd and Hf signatures could have been produced by segregation of melt from a crystallizing magma ocean at upper-mantle pressures early in Earth's history, which would have risen buoyantly and ultimately formed the earliest terrestrial protocrust.
Abstract: Calculations of the energetics of terrestrial accretion indicate that the Earth was extensively molten in its early history. Examination of early Archaean rocks from West Greenland (3.6-3.8 Gyr old) using short-lived 146Sm-142Nd chronometry indicates that an episode of mantle differentiation took place close to the end of accretion (4.46 +/- 0.11 Gyr ago). This has produced a chemically depleted mantle with an Sm/Nd ratio higher than the chondritic value. In contrast, application of 176Lu-176Hf systematics to 3.6-3.8-Gyr-old zircons from West Greenland indicates derivation from a mantle source with a chondritic Lu/Hf ratio. Although an early Sm/Nd fractionation could be explained by basaltic crust formation, magma ocean crystallization or formation of continental crust, the absence of coeval Lu/Hf fractionation is in sharp contrast with the well-known covariant behaviour of Sm/Nd and Lu/Hf ratios in crustal formation processes. Here we show using mineral-melt partitioning data for high-pressure mantle minerals that the observed Nd and Hf signatures could have been produced by segregation of melt from a crystallizing magma ocean at upper-mantle pressures early in Earth's history. This residual melt would have risen buoyantly and ultimately formed the earliest terrestrial protocrust.
126 citations
TL;DR: In this article, the theoretical infrared and Raman spectra of the gibbsite [α-Al(OH) 3 ] were computed using ab initio quantum mechanical calculations and the low-frequency dielectric tensor and the Raman tensors of the Gibbsite were determined using linear response theory.
Abstract: The theoretical infrared (IR) and Raman spectra of gibbsite [α-Al(OH) 3 ] were computed using ab initio quantum mechanical calculations. The low-frequency dielectric tensor and the Raman tensors of gibbsite were determined using linear response theory. The transmission powder IR spectrum was found to strongly depend on the shape of the gibbsite particles. In the region of the OH-stretching bands, an excellent agreement between theory and experiment was obtained, providing an unambiguous interpretation of the OH bands in terms of vibrational modes. In contrast, the assignment of the bands observed at lower frequency is complicated by the significant overlap between neighboring bands together with their sensitivity to particle shape.
125 citations
TL;DR: In this article, the authors investigated the nature and rates of in-situ CO 2 -fluid-rock reactions during an aqueous phase CO 2 injection test at the Lamont-Doherty Earth Observatory test site (New York, USA).
123 citations
TL;DR: A review of previously demonstrated mode-locked thulium-doped fiber sources up to the state-of-the-art can be found in this article along with the aforementioned applications of these sources.
123 citations
Authors
Showing all 903 results
| Name | H-index | Papers | Citations |
|---|---|---|---|
| Claude J. Allègre | 106 | 327 | 35092 |
| Paul Tapponnier | 99 | 294 | 42855 |
| Francesco Mauri | 85 | 352 | 69332 |
| Barbara Romanowicz | 67 | 284 | 14950 |
| Geoffrey C. P. King | 64 | 157 | 17177 |
| Yi-Gang Xu | 64 | 271 | 14292 |
| Jérôme Gaillardet | 63 | 199 | 14878 |
| François Guyot | 61 | 292 | 12444 |
| Georges Calas | 60 | 266 | 10901 |
| Ari P. Seitsonen | 59 | 212 | 45684 |
| Michele Lazzeri | 58 | 140 | 57079 |
| Bernard Bourdon | 58 | 118 | 9962 |
| Gianreto Manatschal | 56 | 200 | 10063 |
| Nikolai M. Shapiro | 56 | 154 | 15508 |
| Guillaume Morin | 55 | 156 | 7218 |