Aqueous fluids play a significant role in the transport of heat and matter in the Earth's crust a... more Aqueous fluids play a significant role in the transport of heat and matter in the Earth's crust and the upper mantle, and high-field-strength elements such as Zr are important geochemical tracers for these processes. However, the dissolution mechanism and complexation of Zr in the fluids at high pressure and temperature are unknown, in part because very low concentrations present severe experimental challenges. Here, we present an experimental setup for in-situ investigation of the coordination environment of elements at low concentrations in aqueous fluids up to 800 °C and 1.5 GPa using XAFS. Experiments were carried out in a modified hydrothermal diamond-anvil cell optimised for the detection of the fluorescence signal. We have investigated the effects of silicate components dissolved in aqueous fluids on the Zr solubility and complexation at high pressure and temperature. The observed Zr concentrations in fluids containing 7-33 wt% Na 2 Si 2 O 5 and variable Al contents were between 75 and 720 ppm at 500 to 750°C and ~300 MPa to ~700 MPa. Initial XAFS results show clear differences between spectra of Zr in an HCl solution and in an H 2 O-Na 2 Si 2 O 5 aqueous fluid, implying considerable differences in the Zr complexation.
Material and energy flux in the lithosphere are largely realized via aqueous fluids with dissolve... more Material and energy flux in the lithosphere are largely realized via aqueous fluids with dissolved electrolyte and silicate components ([1,2,3]). Because fundamental thermodynamic quantities can be derived from PVTx properties, determination of such data for relevant model systems is of central importance for a better understanding of fluids and their interaction with rocks in the lithosphere. Moreover, many high PT experimental techniques require knowledge of the density of the fluid phase to obtain quantitative data.
Fluid-mineral equilibria control the mobility of elements during geologic processes. Consequently... more Fluid-mineral equilibria control the mobility of elements during geologic processes. Consequently, quantitative information about the solubility of minerals in fluids at the pressure-temperature conditions of the Earth's crust and upper mantle is of great ...
The geochemical signature of igneous rocks at convergent plate margins is thought to result from ... more The geochemical signature of igneous rocks at convergent plate margins is thought to result from complex melt formation processes involving aqueous solutions derived from dehydration of the subducted slab. In these processes, the depletion of high-field-strength elements (HFSE) may be controlled by the presence of accessory phases such as zircon and rutile, which can strongly fractionate these elements; however, the
Material and energy flux in the lithosphere are largely realized via aqueous fluids with dissolve... more Material and energy flux in the lithosphere are largely realized via aqueous fluids with dissolved electrolyte and silicate components ([1,2,3]). Because fundamental thermodynamic quantities can be derived from PVTx properties, determination of such data for relevant model systems is of central importance for a better understanding of fluids and their interaction with rocks in the lithosphere. Moreover, many high PT experimental techniques require knowledge of the density of the fluid phase to obtain quantitative data.
Aqueous fluids play a significant role in the transport of heat and matter in the Earth's crust a... more Aqueous fluids play a significant role in the transport of heat and matter in the Earth's crust and the upper mantle, and high-field-strength elements such as Zr are important geochemical tracers for these processes. However, the dissolution mechanism and complexation of Zr in the fluids at high pressure and temperature are unknown, in part because very low concentrations present severe experimental challenges. Here, we present an experimental setup for in-situ investigation of the coordination environment of elements at low concentrations in aqueous fluids up to 800 °C and 1.5 GPa using XAFS. Experiments were carried out in a modified hydrothermal diamond-anvil cell optimised for the detection of the fluorescence signal. We have investigated the effects of silicate components dissolved in aqueous fluids on the Zr solubility and complexation at high pressure and temperature. The observed Zr concentrations in fluids containing 7-33 wt% Na 2 Si 2 O 5 and variable Al contents were between 75 and 720 ppm at 500 to 750°C and ~300 MPa to ~700 MPa. Initial XAFS results show clear differences between spectra of Zr in an HCl solution and in an H 2 O-Na 2 Si 2 O 5 aqueous fluid, implying considerable differences in the Zr complexation.
Material and energy flux in the lithosphere are largely realized via aqueous fluids with dissolve... more Material and energy flux in the lithosphere are largely realized via aqueous fluids with dissolved electrolyte and silicate components ([1,2,3]). Because fundamental thermodynamic quantities can be derived from PVTx properties, determination of such data for relevant model systems is of central importance for a better understanding of fluids and their interaction with rocks in the lithosphere. Moreover, many high PT experimental techniques require knowledge of the density of the fluid phase to obtain quantitative data.
Fluid-mineral equilibria control the mobility of elements during geologic processes. Consequently... more Fluid-mineral equilibria control the mobility of elements during geologic processes. Consequently, quantitative information about the solubility of minerals in fluids at the pressure-temperature conditions of the Earth's crust and upper mantle is of great ...
The geochemical signature of igneous rocks at convergent plate margins is thought to result from ... more The geochemical signature of igneous rocks at convergent plate margins is thought to result from complex melt formation processes involving aqueous solutions derived from dehydration of the subducted slab. In these processes, the depletion of high-field-strength elements (HFSE) may be controlled by the presence of accessory phases such as zircon and rutile, which can strongly fractionate these elements; however, the
Material and energy flux in the lithosphere are largely realized via aqueous fluids with dissolve... more Material and energy flux in the lithosphere are largely realized via aqueous fluids with dissolved electrolyte and silicate components ([1,2,3]). Because fundamental thermodynamic quantities can be derived from PVTx properties, determination of such data for relevant model systems is of central importance for a better understanding of fluids and their interaction with rocks in the lithosphere. Moreover, many high PT experimental techniques require knowledge of the density of the fluid phase to obtain quantitative data.
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Papers by Karen Appel