Anhydrous and hydrous wadsleyite were synthesized at 13.3-13.5 GPa and 1150-1200 °C in a multianvil press and investigated by Fourier transform infrared (FTIR) spectroscopy, single-crystal X-ray refinement (SC-XRD), and electron microprobe analyses (EMPA). The FTIR spectra agree with previous data, i.e., the spectra are dominated by a broad band around 3380 cm -1 , resolvable in three bands 3326 (ν 2 ), 3382 (ν 3 ), and 3546 (ν 4 ) cm -1 besides some weaker OH-bands around 3600 cm -1 . We confirm that wadsleyite incorporates water in the wt% range and that the concentration strongly increases with decreasing temperature when using secondary ion mass spectrometry (SIMS) and Raman spectroscopy. The quantifications combined with FTIR spectra led us to develop the first IR calibration for water in wadsleyite, i.e., calculating an ε i,tot of 73 000 ± 7000 (L mol -1 H 2 O cm -2 ). A SC-XRD determination of hydrous wadsleyite FD0718, bearing 8000 ± 1000 wt ppm H 2 O, certifies the presence of Mg vacancies at the M3 sites as previously suggested. Furthermore, we found maxima in the electron density map close to the O atoms O1 and O3 of an M3 octahedron assuming the anhydrous structure. Based on our new data we suggest that the main protonation in wadsleyite occurs along the O1···O4 (3.1 Å) and O3···O4 (3.05 Å) edges of a vacant M3 octahedron. H-incorporation seems to be random leading to protonation of either two O1, two O3, or one O1 and one O3 of the vacant M3 octahedra. With this assignment, the observed ambient and high-pressure IR pattern can now be explained.

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In the production of calcined kaolin, the on-line monitoring of the calcination reaction is becoming more relevant for the generation of optimal products. In this context, this study aimed to assess the suitability of using infrared (IR) spectroscopy as a potential technique for the on-line characterization of the calcination of kaolin. The transformation of kaolin samples calcined at different temperatures were characterized in the short-wave (SWIR) spectra using the kaolinite crystallinity (Kx) index and the depth of the water spectral feature (1900D). A high correlation between the standard operational procedure for the quality control of calcined kaolin and the Kx index was observed (r = -0.89), as well as with the 1900D parameter (r = -0.96). This study offers a new conceptual approach to the use of SWIR spectroscopy for the characterization the calcination of kaolin, withdrawing the need of using extensive laboratory techniques.

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We performed multi-anvil experiments in the system MgO-SiO 2 ± H 2 O at 13.0-13.7 GPa and 1,025-1,300°C and in the system MgO-FeO-SiO 2 ± H 2 O, under reducing conditions, at 11.0-12.7 GPa and 1200°C, to depict the effect of H 2 O on the P-T-x coordinates of the 410-km discontinuity, i.e. the olivine-wadsleyite phase boundary. The charges were investigated with where wad-ring and ol-ring coexist, we observe, however, an unexpected broadening of the loops with a shift to higher iron contents. In total the stability field of hydrous wad expands in both directions, to lower and higher pressures. Fe 3+ concentrations as determined by EELS are very low and are expected to play no role in the broadening of the loops.

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In a conventional approach, several methods need to be adopted and integrated to understand the geochemical and geophysical signatures of active geothermal systems (e.g., Rybach and Muffler 1981). These methods also apply for greenfield studies and include: (a) geochemical investigations, e.g., application of chemical geothermometers to infer the temperature of the geothermal reservoir; measurement of gas isotopes, such as 3 He/ 4 He, to constrain the origin (mantle or crust) of fluids; (b) drilling of exploration wells; (c) gravity measurements to map any negative anomaly associated with the steam fraction in high-porosity reservoir rocks or to locate zones of lowered density provoked by thermal expansion in magmatic bodies; (d) application of electrical methods such as resistivity to search for zones of higher-salinity fluids; (e) use of seismic methods for the localization of shallow intrusions and estimation of their vertical extension.

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