@article{WilkeAppelVinczeetal.2010, author = {Wilke, Max and Appel, Karen and Vincze, Laszlo and Schmidt, Christian and Borchert, Manuela and Pascarelli, Sakura}, title = {A confocal set-up for micro-XRF and XAFS experiments using diamond-anvil cells}, issn = {0909-0495}, doi = {10.1107/S0909049510023654}, year = {2010}, abstract = {A confocal set-up is presented that improves micro-XRF and XAFS experiment with high-pressure e diamond-anvil cells (DACs) In this experiment a probing volume is defined by the focus of the incoming synchrotron radiation beam and that of a polycapillary X-ray half-lens with a very long working distance, which is placed in front of the fluorescence detector This set-up enhances the quality of the fluorescence and XAFS spectra, and thus the sensitivity for detecting elements at low concentrations. It efficiently suppresses signal from outside the sample chamber, which stems from elastic and inelastic scattering of the incoming beam by the diamond anvils as well as from excitation of fluorescence from the body of the DAC}, language = {en} } @article{KlemmeFeldhausPotapkinetal.2021, author = {Klemme, Stephan and Feldhaus, Michael and Potapkin, Vasily and Wilke, Max and Borchert, Manuela and Louvel, Marion and Loges, Anselm and Rohrbach, Arno and Weitkamp, Petra and Welter, Edmund and Kokh, Maria A. and Schmidt, Christian and Testemale, Denis}, title = {A hydrothermal apparatus for x-ray absorption spectroscopy of hydrothermal fluids at DESY}, series = {Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques}, volume = {92}, journal = {Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques}, number = {6}, publisher = {AIP Publishing}, address = {Melville}, issn = {0034-6748}, doi = {10.1063/5.0044767}, pages = {6}, year = {2021}, abstract = {We present a new autoclave that enables in situ characterization of hydrothermal fluids at high pressures and high temperatures at synchrotron x-ray radiation sources. The autoclave has been specifically designed to enable x-ray absorption spectroscopy in fluids with applications to mineral solubility and element speciation analysis in hydrothermal fluids in complex compositions. However, other applications, such as Raman spectroscopy, in high-pressure fluids are also possible with the autoclave. First experiments were run at pressures between 100 and 600 bars and at temperatures between 25 degrees C and 550 degrees C, and preliminary results on scheelite dissolution in fluids of different compositions show that the autoclave is well suited to study the behavior of ore-forming metals at P-T conditions relevant to the Earth's crust.}, language = {en} } @article{FargesDjanarthanydeWispelaereetal.2005, author = {Farges, Francois and Djanarthany, S and de Wispelaere, S and Munoz, Manuel and Magassouba, B and Haddi, A and Wilke, Max and Schmidt, C. and Borchert, Manuela and Trocellier, P and Crichton, W and Simionovici, Alexandre and Petit, Pierre-Emanuel and Mezouar, Mohamed and Etcheverry, M. P. and Pallot-Frossard, I and Bargar, John Reeder and Brown, G. E. and Grolimund, D and Scheidegger, A}, title = {Water in silicate glasses and melts of environmental interest : from volcanoes to cathedrals}, year = {2005}, abstract = {In silicate glasses and melts, water acts according to two main processes. First, it can be dissolved in high temperature/high pressure melts. Second, it constitutes a weathering agent on the glass surface. A number of in-situ x- ray absorption fine structure (XAFS) studies for Fe, Ni, Zr, Th and U show that the more charged cations (Zr, Nb, Mo, Ta, Sn, Th and U) are little affected by the presence of dissolved water in the melt. In contrast, divalent iron and nickel are highly sensitive to the presence of water, which enhance nucleation processes, for example, of phyllosilicates at the angstrom-scale. Such information provides additional constraints on the role of water deep in the Earth, particularly in magmatology. By contrast, the weathering of glass surfaces by water can be studied from a durability perspective. Experimental weathering experiments Of nuclear waste glasses performed in the laboratory show a variety of surface enrichments (carbon, chlorine, alkalis, iron) after exposure to atmospheric fluids and moisture. Mn-, and Fe-surface enrichments of analogous glasses of the XIVth century are related to the formation of Mn and Fe oxy/ hydroxides on the surface. The impact on the glass darkening is considered in terms of urban pollution and mass tourism}, language = {en} } @article{BorchertWilkeSchmidtetal.2009, author = {Borchert, Manuela and Wilke, Max and Schmidt, Christian and Rickers, Karen}, title = {Partitioning and equilibration of Rb and Sr between silicate melts and aqueous fluids}, issn = {0009-2541}, doi = {10.1016/j.chemgeo.2008.10.019}, year = {2009}, abstract = {Trace element concentrations in aqueous fluids in equilibrium with haplogranitic melt were determined in situ at elevated P-T conditions using hydrothermal diamond-anvil cells and synchrotron-radiation XRF microanalyses. Time- resolved analyses showed that the Rb and Sr concentrations in the fluids became constant in less than 2000 s at all temperatures (500 to 780 degrees C). Although fluid-melt equilibration was very rapid, the change in the concentration of both elements in the fluid with temperature was fairly small (a slight increase for Rb and a slight decrease for Sr). This permitted partitioning data for Rb and Sr between haplogranitic melt and H2O or NaCl+KCl+HCl aqueous solutions at 750 degrees C and 200 to 700 MPa to be obtained from EMP analyses of the quenched melt and the in situ SR-XRF analyses of the equilibrated fluid. The resulting D-Rb(f/m) and D-Sr(f/m) were 0.01 +/- 0.002 and 0.006 +/- 0.001 for water as starting fluid, and increased to 0.47 +/- 0.08 and 0.23 +/- 0.03 for 3.56 m (NaCl+KCl)+0.04 in HCl at pressures of 224 to 360 MPa. In the experiments with H2O as starting fluid, the partition coefficients increased with pressure, i.e. D- Rb(f/m) from 0.01 +/- 0.002 to 0.22 +/- 0.02 and D-Sr(f/m) from 0.006 0.001 to 0.02 +/- 0.005 with a change in pressure from 360 to 700 MPa. At pressures to 360 MPa, the Rb/Sr ratio in the fluid was found to be independent of the initial salt concentration (Rb/Sr = 1.45 +/- 0.6). This ratio increased to 7.89 +/- 1.95 at 700 MPa in experiments with chloride free fluids, which indicates different changes in the Rb and Sr speciation with pressure.}, language = {en} } @article{BorchertWilkeSchmidtetal.2010, author = {Borchert, Manuela and Wilke, Max and Schmidt, Christian and Rickers, Karen}, title = {Rb and Sr partitioning between haplogranitic melts and aqueous solutions}, issn = {0016-7037}, doi = {10.1016/j.gca.2009.10.033}, year = {2010}, abstract = {Rubidium and strontium partitioning experiments between haplogranitic melts and aqueous fluids (water or 1.16- 3.56 m (NaCl + KCl) +/- HCl) were conducted at 750-950 degrees C and 0.2-1.4 GPa to investigate the effects of melt and fluid composition, pressure, and temperature. In addition, we studied if the applied technique (rapid and slow quench, and in-situ determination of trace element concentration in the fluid) has a bearing on the obtained data. There is good agreement of the data from different techniques for chloridic solutions, whereas back reactions between fluid and Melt upon cooling have a significant effect on results from the experiments with water. The Rb fluid-melt partition coefficient shows no recognizable dependence on melt composition and temperature. For chloridic Solutions, it is similar to 0.4, independent of pressure. In experiments with water, it is one to two orders of magnitude lower and increases with pressure. The strontium fluid-melt partition coefficient does not depend on temperature. It increases slightly with pressure in Cl free experiments. In chloridic fluids, there is a sharp increase in the Sr partition coefficient with the alumina saturation index (ASI) from 0.003 at an ASI of 0.8 to a maximum of 0.3 at an ASI of 1.05. At higher ASI, it decreases slightly to 0.2 at an ASI of 1.6. It is one to two orders of magnitude higher in chloridic fluids compared to those found in H2O experiments. The Rb/Sr ratio in non-chloridic solutions in equilibrium with metaluminous melts increases with pressure, whereas the Rb/Sr ratio in chloridic fluids is independent of pressure and decreases with fluid salinity. The obtained fluid-melt partition coefficients are in good agreement with data from natural cogenetic fluid and melt inclusions. Numerical modeling shows that although the Rb/Sr ratio in the residual melt is particularly sensitive to the degree of fractional crystallization, exsolution of a fluid phase, and associated fluid-melt partitioning is not a significant factor controlling Rb and Sr concentrations in the residual melt during crystallization of most granitoids.}, language = {en} } @article{BorchertWilkeSchmidtetal.2010, author = {Borchert, Manuela and Wilke, Max and Schmidt, Christian and Cauzid, Jean and Tucoulou, R{\´e}mi}, title = {Partitioning of Ba, La, Yb and Y between haplogranitic melts and aqueous solutions : an experimental study}, issn = {0009-2541}, doi = {10.1016/j.chemgeo.2010.06.009}, year = {2010}, abstract = {Barium, lanthanum, ytterbium, and yttrium partitioning experiments between fluid-saturated haplogranitic melts and aqueous solutions were conducted at 750 to 950 degrees C and 0.2 to 1 GPa to investigate the effects of melt and fluid composition, pressure, and temperature. Partition coefficients were determined using different experimental methods. On one hand quenched experiments were performed, and on the other hand, trace element contents in the aqueous fluid were determined directly using a hydrothermal diamond-anvil cell and synchrotron radiation X-ray fluorescence microanalysis of K-lines. The latter required a high excitation energy of 50 key due to the high energies necessary to excite the K-lines of the studied elements. The data from these two techniques showed good agreement for chloridic solutions, whereas quenching had a significant effect on results of the experiments with only water in the case of Ba. In Cl-free experiments, lanthanum and yttrium, trace element contents were even below detection limit in the quenched fluids, whereas small concentrations were detected in comparable in-situ experiments. This distinct difference is likely due to back reactions between fluid and melt upon cooling. The partitioning data of all elements show no dependence on the temperature and only small dependence on pressure. In contrast, the partitioning is strongly influenced by the composition of the starting fluid and melt. For chloridic fluids, there was a sharp increase in the Ba, La, Y and Yb partition coefficients with the alumina saturation index (ASI). The Ba partition coefficient increased from 0.002 at an ASI of 0.8 to 0.55 at an ASI of 1.07. At higher ASI, it decreased slightly to 0.2 at an ASI of similar to 1.3. Likewise, it was one to two orders of magnitude higher in chloridic fluids compared to those found in H2O experiments. Fluid-melt partition coefficients of La and Y increased from 0.002 at an ASI of similar to 0.8 to similar to 0.1 at an ASI of 1.2. In the same ASI range, the Yb partition coefficient increased to a maximum value of 0.02. Even at high salinities all elements fractionate into the melt. The compositional dependence of the partitioning data imply that both melt composition and fluid composition have a strong influence on trace element behavior and that complexation of Ba. REE and Y tin the fluid is not only controlled by the presence of Cl- in the fluid. Instead, interaction of these elements with major melt components dissolved in the fluid is very likely.}, language = {en} }