TY - JOUR A1 - Wilke, Max A1 - Appel, Karen A1 - Vincze, Laszlo A1 - Schmidt, Christian A1 - Borchert, Manuela A1 - Pascarelli, Sakura T1 - A confocal set-up for micro-XRF and XAFS experiments using diamond-anvil cells N2 - 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 Y1 - 2010 UR - http://journals.iucr.org/s/journalhomepage.html U6 - https://doi.org/10.1107/S0909049510023654 SN - 0909-0495 ER - TY - THES A1 - Borchert, Manuela T1 - Interactions between aqueous fluids and silicate melts : equilibration, partitioning and complexation of trace elements T1 - Wechselwirkungen zwischen wässrigen Fluiden und silikatischen Schmelzen : Verteilung von Spurenelementen N2 - The origin and evolution of granites has been widely studied because granitoid rocks constitute a major portion of the Earth ́s crust. The formation of granitic magma is, besides temperature mainly triggered by the water content of these rocks. The presence of water in magmas plays an important role due to the ability of aqueous fluids to change the chemical composition of the magma. The exsolution of aqueous fluids from melts is closely linked to a fractionation of elements between the two phases. Then, aqueous fluids migrate to shallower parts of the Earth ́s crust because of it ́s lower density compared to that of melts and adjacent rocks. This process separates fluids and melts, and furthermore, during the ascent, aqueous fluids can react with the adjacent rocks and alter their chemical signature. This is particularly impor- tant during the formation of magmatic-hydrothermal ore deposits or in the late stages of the evolution of magmatic complexes. For a deeper insight to these processes, it is essential to improve our knowledge on element behavior in such systems. In particular, trace elements are used for these studies and petrogenetic interpretations because, unlike major elements, they are not essential for the stability of the phases involved and often reflect magmatic processes with less ambiguity. However, for the majority of important trace elements, the dependence of the geochemical behavior on temperature, pressure, and in particular on the composition of the system are only incompletely or not at all experimentally studied. Former studies often fo- cus on the determination of fluid−melt partition coefficients (Df/m=cfluid/cmelt) of economically interesting elements, e.g., Mo, Sn, Cu, and there are some partitioning data available for ele- ments that are also commonly used for petrological interpretations. At present, no systematic experimental data on trace element behavior in fluid−melt systems as function of pressure, temperature, and chemical composition are available. Additionally, almost all existing data are based on the analysis of quenched phases. This results in substantial uncertainties, particularly for the quenched aqueous fluid because trace element concentrations may change upon cooling. The objective of this PhD thesis consisted in the study of fluid−melt partition coefficients between aqueous solutions and granitic melts for different trace elements (Rb, Sr, Ba, La, Y, and Yb) as a function of temperature, pressure, salinity of the fluid, composition of the melt, and experimental and analytical approach. The latter included the refinement of an existing method to measure trace element concentrations in fluids equilibrated with silicate melts di- rectly at elevated pressures and temperatures using a hydrothermal diamond-anvil cell and synchrotron radiation X-ray fluorescence microanalysis. The application of this in-situ method enables to avoid the main source of error in data from quench experiments, i.e., trace element concentration in the fluid. A comparison of the in-situ results to data of conventional quench experiments allows a critical evaluation of quench data from this study and literature data. In detail, starting materials consisted of a suite of trace element doped haplogranitic glasses with ASI varying between 0.8 and 1.4 and H2O or a chloridic solution with m NaCl/KCl=1 and different salinities (1.16 to 3.56 m (NaCl+KCl)). Experiments were performed at 750 to 950◦C and 0.2 or 0.5 GPa using conventional quench devices (externally and internally heated pressure vessels) with different quench rates, and at 750◦C and 0.2 to 1.4 GPa with in-situ analysis of the trace element concentration in the fluids. The fluid−melt partitioning data of all studied trace elements show 1. a preference for the melt (Df/m < 1) at all studied conditions, 2. one to two orders of magnitude higher Df/m using chloridic solutions compared to experiments with H2O, 3. a clear dependence on the melt composition for fluid−melt partitioning of Sr, Ba, La, Y, and Yb in experiments using chloridic solutions, 4. quench rate−related differences of fluid−melt partition coefficients of Rb and Sr, and 5. distinctly higher fluid−melt partitioning data obtained from in-situ experiments than from comparable quench runs, particularly in the case of H2O as starting solution. The data point to a preference of all studied trace elements for the melt even at fairly high salinities, which contrasts with other experimental studies, but is supported by data from studies of natural co-genetically trapped fluid and melt inclusions. The in-situ measurements of trace element concentrations in the fluid verify that aqueous fluids will change their composition upon cooling, which is in particular important for Cl free systems. The distinct differences of the in-situ results to quench data of this study as well as to data from the literature signify the im- portance of a careful fluid sampling and analysis. Therefore, the direct measurement of trace element contents in fluids equilibrated with silicate melts at elevated PT conditions represents an important development to obtain more reliable fluid−melt partition coefficients. For further improvement, both the aqueous fluid and the silicate melt need to be analyzed in-situ because partitioning data that are based on the direct measurement of the trace element content in the fluid and analysis of a quenched melt are still not completely free of quench effects. At present, all available data on element complexation in aqueous fluids in equilibrium with silicate melts at high PT are indirectly derived from partitioning data, which involves in these experiments assumptions on the species present in the fluid. However, the activities of chemical components in these partitioning experiments are not well constrained, which is required for the definition of exchange equilibria between melt and fluid species. For example, the melt-dependent variation of partition coefficient observed for Sr imply that this element can not only be complexed by Cl− as suggested previously. The data indicate a more complicated complexation of Sr in the aqueous fluid. To verify this hypothesis, the in-situ setup was also used to determine strontium complexation in fluids equilibrated with silicate melts at desired PT conditions by the application of X-ray absorption near edge structure (XANES) spectroscopy. First results show a strong effect of both fluid and melt composition on the resulting XANES spectra, which indicates different complexation environments for Sr. N2 - Die Entstehung und Entwicklung von Graniten steht seit Jahrzehnten im Fokus vieler geologischer Studien, da sich die Erdkruste zu großen Teilen aus granitoiden Gesteinen zusammensetzt. Von besonderer Bedeutung für die Bildung von granitischen Schmelzen ist neben der Temperatur, der Wassergehalt der Schmelze, da dieser Parameter die chemische Zusammensetzung der Schmelze entscheidend verändern kann. Die Entmischung wässriger Fluide aus Schmelzen führt zur Neuverteilung von Elementen zwischen diesen Phasen. Bedingt durch die geringere Dichte des wässrigen Fluids im Vergleich zur Schmelze und dem Nebengestein, beginnt dieses aus tieferen Erdschichten aufzusteigen. Damit verknüpft ist nicht nur eine räumliche Trennung von Schmelze und Fluid, sondern auch die Alterierung des Nebengestein. Dieser Prozess ist insbesondere bei der Bildung von magmatisch-hydrothermalen Lagerstätten und in späten Entwicklungsstadien magmatischer Komplexe wichtig. Für ein detailliertes Verständnis dieser Prozesse ist es notwendig, das Elementverhalten in solchen Systemen in Abhängigkeit von Parametern wie Temperatur, Druck und chemischer Zusammensetzung des Systems experimentell zu untersuchen, und Elementverteilungskoeffizienten als Funktion dieser Variablen zu bestimmen. Für die Untersuchungen sind insbesondere Spurenelemente geeignet, da diese im Gegensatz zu Hauptelementen nicht essentiell für die Stabilität weiterer auftretender Phasen sind, aber sehr sensibel auf Änderungen intensiver Variablen reagieren können. Zudem werden bei geochemischen Mineral- und Gesteinsanalysen viele Spurenelemente, Spurenelementverhältnisse, und Spurenelementisotope als petrogenetische Indikatoren verwendet, d.h. diese Daten liefern Informationen darüber, wann und in welcher Tiefe und bei welchen chemischen Bedingungen ein Gestein gebildet worden ist, und welche weiteren Prozesse es auf dem Weg zur Erdoberfläche durchlaufen hat. Allerdings sind für vie- le Spurenelemente die Abhängigkeiten der Verteilung zwischen Fluiden und Schmelzen von intensiven Variablen nicht, oder nur unzureichend experimentell untersucht worden. Zusätzlich dazu basiert die Mehrheit der experimentell gewonnenen Verteilungskoeffizienten und deren Interpretation, insbesondere hinsichtlich der Elementkomplexierung im Fluid, auf der Analyse von schnell abgekühlten Phasen. Bisher ist nicht geklärt, ob solche Analysen repräsentativ sind für die Zusammensetzungen der Phasen bei hohen Drücken und Temperaturen. Das Ziel dieser Studie war die Erarbeitung eines experimentellen Datensatzes zur Spu- renelementverteilung zwischen granitischen Schmelzen und wässrigen Fluiden in Abhängigkeit von der Schmelzzusammensetzung, der Salinität des Fluids, des Drucks und der Temperatur. Ein Hauptanliegen der Arbeit bestand in der Weiterentwicklung einer experimentellen Methode bei welcher der Spurenelementgehalt im Fluid in-situ, d.h. unter hohen Drücken und Temperaturen, und im Gleichgewicht mit einer silikatischen Schmelze bestimmt wird. Die so gewonnenen Daten können anschließend mit den Resultaten von Abkühlexperimenten vergli- chen werden, um diese und auch Literaturdaten kritisch zu bewerten. Die Daten aller unter- suchten Spurenelemente dieser Arbeit (Rb, Sr, Ba, La, Y und Yb) zeigen: 1. unter den untersuchten Bedingungen eine Präferenz für die Schmelze unabhängig von der chemischen Zusammensetzung von Schmelze und Fluid, Druck oder Temperatur, 2. die Verwendung von chloridhaltigen Fluiden kann die Verteilungskoeffizienten um 1 bis 2 Größenordnungen anheben und 3. für die Verteilungskoeffizienten von Sr, Ba, La, Y und Yb eine starke Abhängigkeit von der Schmelzzusammensetzung im chloridischen System. Der Vergleich der Daten der verschiedenen Methoden zeigt, dass insbesondere für chloridfreie Fluide große Diskrepanzen zwischen den in-situ Daten und Analysen von abgeschreckten Proben bestehen. Dieses Ergebnis beweist eindeutig, dass beim Abschrecken der Proben Rückreaktionen stattfinden, und dass Daten, welche auf Analysen abgeschreckter Fluide basieren, nur eingeschränkt verwendet werden sollten. Die Variation der Verteilungskoeffizienten von Sr, Ba, La, Yb, und Y als Funktion der Schmelzzusammensetzung ist entweder auf eine Änderung der Komplexierung im Fluid und/oder einen anderen veränderten Einbau dieser Elemente in die Schmelze zurückzuführen. Daher wurde im Rahmen dieser Arbeit erstmals versucht, die Elementkomplexierung in silikatischen Fluiden direkt bei hohen Temperaturen und Drücken zu bestimmen. Die Daten für Sr zeigen, dass abhängig von der Schmelzzusammensetzung unterschiedliche Komplexe stabil sein müssen. KW - Spurenelement-Partitionierung KW - Fluid-Schmelze Wechselwirkung KW - HP-HT Experimente KW - In-Situ-Analyse KW - HDAC KW - trace element partitioning KW - fluid-melt interaction KW - HP-HT experiments KW - in-situ analysis KW - HDAC Y1 - 2010 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-42088 ER - TY - JOUR A1 - Borchert, Manuela A1 - Wilke, Max A1 - Schmidt, Christian A1 - Rickers, Karen T1 - Partitioning and equilibration of Rb and Sr between silicate melts and aqueous fluids N2 - 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. Y1 - 2009 UR - http://www.sciencedirect.com/science/journal/00092541 U6 - https://doi.org/10.1016/j.chemgeo.2008.10.019 SN - 0009-2541 ER - TY - JOUR A1 - Borchert, Manuela A1 - Wilke, Max A1 - Schmidt, Christian A1 - Cauzid, Jean A1 - Tucoulou, Rémi T1 - Partitioning of Ba, La, Yb and Y between haplogranitic melts and aqueous solutions : an experimental study N2 - 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. Y1 - 2010 UR - http://www.sciencedirect.com/science/journal/00092541 U6 - https://doi.org/10.1016/j.chemgeo.2010.06.009 SN - 0009-2541 ER - TY - JOUR A1 - Borchert, Manuela A1 - Wilke, Max A1 - Schmidt, Christian A1 - Rickers, Karen T1 - Rb and Sr partitioning between haplogranitic melts and aqueous solutions N2 - 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. Y1 - 2010 UR - http://www.sciencedirect.com/science/journal/00167037 U6 - https://doi.org/10.1016/j.gca.2009.10.033 SN - 0016-7037 ER - TY - JOUR A1 - Farges, Francois A1 - Djanarthany, S A1 - de Wispelaere, S A1 - Munoz, Manuel A1 - Magassouba, B A1 - Haddi, A A1 - Wilke, Max A1 - Schmidt, C. A1 - Borchert, Manuela A1 - Trocellier, P A1 - Crichton, W A1 - Simionovici, Alexandre A1 - Petit, Pierre-Emanuel A1 - Mezouar, Mohamed A1 - Etcheverry, M. P. A1 - Pallot-Frossard, I A1 - Bargar, John Reeder A1 - Brown, G. E. A1 - Grolimund, D A1 - Scheidegger, A T1 - Water in silicate glasses and melts of environmental interest : from volcanoes to cathedrals N2 - 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 Y1 - 2005 ER - TY - JOUR A1 - Klemme, Stephan A1 - Feldhaus, Michael A1 - Potapkin, Vasily A1 - Wilke, Max A1 - Borchert, Manuela A1 - Louvel, Marion A1 - Loges, Anselm A1 - Rohrbach, Arno A1 - Weitkamp, Petra A1 - Welter, Edmund A1 - Kokh, Maria A. A1 - Schmidt, Christian A1 - Testemale, Denis T1 - A hydrothermal apparatus for x-ray absorption spectroscopy of hydrothermal fluids at DESY JF - Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques N2 - 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. Y1 - 2021 U6 - https://doi.org/10.1063/5.0044767 SN - 0034-6748 SN - 1089-7623 VL - 92 IS - 6 PB - AIP Publishing CY - Melville ER -