The Solubility of Tugarinovite (MoO 2 ) in H 2 O at Elevated Temperatures and Pressures (original) (raw)
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Solubility of tugarinovite (MoO2) was measured in water under conditions of extreme temperature and pressure using synchrotron X-ray fluorescence (SXRF). Synthetic MoO2 was investigated in a hydrothermal diamond anvil cell (HDAC) at a pressure-temperature range which is typical of porphyry Mo ore formation. Solubility of tugarinovite was measured at temperatures between 400 and 800 C and at pressures ranging between 95 and 480 MPa. The results of this study are also relevant to understanding the corrosion behavior of Mo-bearing candidate steel alloys to be used in the next generation of supercritical-water-cooled reactors (SCWR). This study demonstrates the potential of the SXRF method for in situ solubility measurements of sparingly soluble oxide minerals at elevated temperatures and pressures. Although SXRF has been successfully used in solubility studies to analyze fluid within an HDAC, the analysis of light elements (Z<28) using XRF has been limited or impossible. To overcome this limitation, a new method combining an inductively coupled plasma-mass spectrometer (ICP-MS) and a newly designed hydrothermal diamond anvil cell (HDAC) has been introduced. The advantage of the HDAC-ICP-MS technique over in situ SXRF technique is its superior sensitivity and detection capability of light elements such as Cr, Ti, Si etc. The results obtained from solutions equilibrated with eskolaite (Cr2O3) at 629 C and 450 MPa, and tugarinovite (MoO2) at 750 C and 1 GPa are presented to demonstrate the potential of this new technique to study the solubility of sparingly soluble materials at extreme temperatures and pressures. ii Acknowledgments I am sincerely grateful to my supervisor Dr. Alan J. Anderson for his unconditional support and encouragement, his assistance throughout the project and his patience to bear with me all along in my master's program. Dr. Matthias Klemm is acknowledged for supplying the synthetic MoO2 samples. Dr. Steve Heald is thanked for his assistance at Sector 20 of the Advanced Photon Source. Dr. Chris McFarlane and Brandon Boucher are thanked for their assistance with ICP-MS analysis.
Geochimica et Cosmochimica Acta, 2012
Solubility experiments of molybdenite in single-phase, NaCl (±HCl)-bearing aqueous fluids were conducted at 600-800°C, 200 MPa and various fO 2 -fS 2 conditions imposed by mineral buffers. Small aliquots of fluids were trapped after 1-7 days of equilibration as synthetic fluid inclusions in quartz and subsequently analyzed by laser-ablation ICP MS. Measured Mo concentrations range from 20 to 3000 ppm by weight and increase with increasing temperature, NaCl concentration and oxygen fugacity, but decrease with increasing sulfur fugacity. Our solubility data can be fitted by the following equation:
Solubility of molybdenite in hydrous granitic melts at 800°C, 100–200MPa
Geochimica et Cosmochimica Acta, 2014
The solubility of molybdenite, MoS 2 , in fluid-saturated, subaluminous to peraluminous granitic melts was determined experimentally using rapid-quench cold-seal pressure vessels at 800°C and 100-200 MPa, and analysis by laser-ablation ICP-MS. Molybdenite solubility seems to be independent of pressure, but it shows strong variations with oxygen and sulfur fugacity. At constant log fS 2 = À1.3 it increases from 0.1-0.7 ppm by weight Mo at the Co-CoO buffer to 29-38 ppm by weight Mo near the MnO-Mn 3 O 4 buffer. The solubility isopleths are nearly parallel to the pyrrhotite-magnetite equilibrium, along which the solubility varies only slightly, from 10 ppmw Mo at the quartz-fayalite-magnetite buffer to 29-38 ppmw Mo at the MnO-Mn 3 O 4 buffer. The observed solubility variations are consistent with the equilibrium MoS 2 (s) + 3/2O 2 = MoO 3 (l) + S 2 and thus confirm that molybdenum(VI) oxide is the predominant species in subaluminous silicate melts at log fO 2 = À16 to À11. In addition, the experimental results are well reproduced by a simple thermodynamic model employing the Burnham eight-oxygen formulation for silicate melt species and assuming ideal mixing of dissolved MoO 3 . The thermodynamic calibration can be used to estimate the molybdenum solubility in subaluminous silicic melts or, for pyrrhotite-and molybdenite-saturated assemblages, the oxygen and sulfur fugacities during magma crystallization.
Chemical Geology, 2000
A hydrothermal diamond anvil cell (HDAC) has been modified by drilling holes with a laser to within 150 μm of the anvil face to minimize the loss of X-rays due to absorption and scatter by diamond. This modification enables acquisition of K-edge X-ray absorption fine structure (XAFS) spectra from first-row transition metal ions in aqueous solutions at temperatures ranging from 25°C to 660°C and pressures up to 800 MPa. These pressure–temperature (P–T) conditions are more than sufficient for carrying out experimental measurements that can provide data valuable in the interpretation of fluid inclusions in minerals found in ore-forming hydrothermal systems as well as other important lithospheric processes involving water.
Keywords: rutile solubility high-field-strength elements ti mobility fluid flow Rutile is an important mineral host for high-field strength elements, so its solubility in geologic fluids at high pressure and temperature plays an important role in the crustal and mantle processes that control the terrestrial cycling of these elements. However, experimental measurements of rutile solubility are in conflict by a factor of more than 100 at most studied conditions. We performed new measurements of rutile solubility in H 2 O-albite and H 2 O-Na 2 Si 3 O 7 (NS3) fluids by in-situ synchrotron radiation X-ray fluorescence spectroscopy using modified Bassett-type hydrothermal diamond-anvil cells. Minimum detection limits were 1.9 and 2.3 ppm Ti by weight for the two cells. Three albite-H 2 O experiments at starting bulk compositions of 2.7, 6.7 and 10.3 wt.% albite involved spectral acquisition at rutile saturation in the presence of albite crystals, melt, or a single homogeneous fluid phase; after accounting for the additional phases, corrected fluid compositions were 0.6 to 7.5 wt.% dissolved silicate over the run conditions. At ≤2.7 wt.% albite, rutile dissolution rate was slow and steady state was not achieved at 600-800°C; however, at higher dissolved albite contents, constant solubility with time was observed. Rutile solubilities in the presence of a single fluid phase at 700°C, 0.79 GPa, 5.4 wt.% albite, and at 800°C, 1.10 GPa, 6.7 wt.% albite, were 37 ± 2 and 156 ± 6 ppm, respectively. These data agree with results acquired using hydrothermal piston-cylinder methods with long run times and suppression of new crystal growth, but not with data derived from visual observation in hydrothermal diamond-anvil cells. This discrepancy is likely due to lack of equilibrium in the latter approach. Two experiments in 10 and 30 wt.% NS3 at 660-800°C, 0.5 ± 0.1 GPa, show extreme concentration-dependent enhancement of rutile solubility to ∼ 4500 ppm. The data indicate a strong positive correlation between rutile solubility and Na/Al. Because (Na + K)/Al is likely to be greater than unity in aqueous fluids at high pressure and temperature due to incongruent dissolution of albite and micas, the increase in rutile solubility along the albite-NS3 join points to the possibility of significant Ti transport by silicate-bearing aqueous fluids in the lower crust and upper mantle.
Geochimica et Cosmochimica Acta, 2006
The solubility of natural, near-end-member wollastonite-I (>99.5% CaSiO 3) has been determined at temperatures from 400 to 800°C and pressures between 0.8 and 5 GPa in piston-cylinder apparatus with the weight-loss method. Chemical analysis of quench products and optical monitoring in a hydrothermal diamond anvil cell demonstrates that no additional phases form during dissolution. Wollastonite-I, therefore, dissolves congruently in the pressure-temperature range investigated. The solubility of CaSiO 3 varies between 0.175 and 13.485 wt% and increases systematically with both temperature and pressure up to 3.0 GPa. Above 3.0 GPa wollastonite-I reacts rapidly to the high-pressure modification wollastonite-II. No obvious trends are evident in the solubility of wollastonite-II, with values between 1.93 and 10.61 wt%. The systematics of wollastonite-I solubility can be described well by a composite polynomial expression that leads to isothermal linear correlation with the density of water. The molality of dissolved wollastonite-I in pure water is then
New Measurements of the Solubility of Metal Oxides at High Temperature
2000
The results of high temperature solubility studies at ORNL are presented in which mainly direct pH measurements were made of the aqueous systems involvin g the crystalline solid phases: A1(OH)3, AlOOH, Fe304, Mg(OH)2, Nd(OH)3, and ZnO. ExampIes are highlighted of specific phenomena such as: the kinetics of gibbsite and boehmite dissolution and precipitation; the appearance of metastable equilibria in the dissolution of Fe304; the extremely rapid precipitation of crystalline brucite, Mg(OH)2; and anomalies in the apparent solubility profiles of AlO and ZnO. Genera1 trends associated with the effects of temperature and ionic strength are mentioned. Some of the potentiometric investigations were augmented by conventional batch {AIO(OH) and ZnO}, and flow-through column (ZnO> experiments. In the additional case of ZnCr204, the extremely low solubility of this spine1 permitted application of only the latter technique and these results are discussed in terms ofthe measured chromium levels that resulted from incongruent dissolution.
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.