Hydrothermal Pressure Vessel Research Articles

Assimilation of xenocrystic apatite in peraluminous granitic magmas

Abstract Apatite is a ubiquitous phase in granite plutons and in most adjacent country rocks, thus contamination of a granite magma with wall-rock material results in two genetic types of apatite in the magma: cognate and foreign. These two textural and chemical varieties of apatite undergo textural and compositional changes to reach physical and chemical equilibrium (perfect assimilation) in the melt. Our experiments replicate the conditions in such contaminated granites. The starting materials consist of a peraluminous synthetic SiO2-Al2O3-Na2O-K2O (SANK 1.3) granite gel with A/NK of 1.3, synthetic F-apatite, synthetic Cl-apatite, and natural Durango apatite. Initial experiments in cold-seal hydrothermal pressure vessels at magmatically realistic temperatures of 750 °C and pressures of 200 MPa produced negligible reactions, even after run times of 2000 h. Instead, we used an argon-pressurized internally heated pressure vessel with a rapid-quench setup at temperatures of 1200 °C, pressure of 200 MPa, and run durations of 192 h. An advantage of this high temperature is that it exceeds the liquidus for quartz and feldspar; therefore, apatite is the only solid phase in the run products. The starting composition of each run was 90 wt% SANK 1.3 granite gel and 10 wt% crushed apatite (consisting of one, two, or three varieties), with and without 4 wt% added H2O. Run products were examined by SEM for texture and by EMPA and LA-ICP-MS for composition. The starting synthetic granite composition contains no Ca, F, Cl, or REEs thus, in every run, apatite was initially undersaturated in the melt. In all experiments, most large apatite grains consisted of anhedral shards with rounded corners, most small apatite grains were round, and a small proportion of apatite grains developed one or more crystal faces. In experiments with two or three apatite compositions, the run-product apatite grains had compositions intermediate between those of the starting-material grains, and they were homogeneous with respect to Cl, and probably F, but not with respect to REEs. The processes to reach textural equilibrium consist of dissolution until the melt is saturated in apatite, followed by Ostwald ripening to eliminate small grains and to develop crystal faces on larger ones. The processes to reach chemical equilibrium consist of dissolution of apatite, diffusion of cations (Ca, P, REE) and anions (F, Cl, OH) through the silicate melt, and solid-state diffusion in the undissolved apatite grains. The halogens approached chemical equilibrium in all experiments, but in the experiments containing Durango apatite, the REEs have not. Models involving radial diffusion into spherical apatite grains at the temperatures of the experiments show complete re-equilibration of the halogens, but changes in the REE concentrations affecting only the outer few micrometers. We conclude that the rate of chemical equilibrium for the halogens is greater than the rate of physical equilibrium for texture, which in turn is greater the rate of chemical equilibrium for REEs. We illustrate these processes with a natural example of contaminated granite from the South Mountain Batholith in Nova Scotia. Given that all granites are contaminated rocks, we propose that future petrogenetic studies focus on developing techniques for a minerals-based quantitative estimation of contamination (QEC).

Improved citric acid-derived carbon dots synthesis through microwave-based heating in a hydrothermal pressure vessel.

Carbon dots (CDs) are a diverse and wide-reaching field of study which encompasses multiple scientific disciplines. This, along with their extensive applications, calls for the need to continually seek to improve their synthesis efficiency. To this end, we focused upon the effects of altering the heating method on the characteristics and quality of the final CD product. In our approach, two different versions of heating techniques were used including the common oven-based hydrothermal method and a microwave (MW)-assisted hydrothermal method. The MW-assisted heating involved the implementation of a pressure vessel (similar to oven hydrothermal vessel) for improved yield of luminescent CDs. We found that this MW method yielded CDs of bright intensity with comparable shape, size, and dispersity to that produced using conventional hydrothermal methods. Specifically, the CDs average particle diameters were determined to be between 1.8 and 2.0 nm for either method. The MW method also demonstrated certain advantages over the oven method in terms of required reaction time and particle yield. The total reaction and cooldown time was reduced by ∼75% (with ideal MW heating time) and an estimation of the average CDs particle density revealed that the MW method was able to produce approximately 1.2 times more particles than the oven method in less time. Correcting for the same processing time, larger yields are available in microwave synthesis. We were able to also demonstrate that both versions of synthesized CDs can serve as viable fluorescence probes for in vitro imaging experiments due to the fact that, under the determined working conditions, their fluorescence emission is significantly greater than that of cell autofluorescence [oven: p = 1.47 × 10-27 (blue), p = 6.98 × 10-4 (green); 60 second MW: p = 7.59 × 10-10 (blue), p = 3.03 × 10-4 (green)] and the CDs were not cytotoxic. This rapid, simple synthesis approach can be applied to other forms of carbon dots and serves as a high-yield alternative to hydrothermal synthesis.

Experimental study on the pseudobinary H2O + NaAlSi3O8 at 600–800 °C and 0.3–2.4 GPa

The pseudobinary H2O+NaAlSi3O8 was studied at compositions between 35 and 66 mass% NaAlSi3O8, at temperatures between 600 and 804°C, and at pressures ranging from 0.3 to 2.41GPa using a hydrothermal diamond-anvil cell (HDAC), cold-seal hydrothermal pressure vessels (CSPVs), and a piston-cylinder apparatus (PC). We propose a revised pseudosection for bulk compositions near 40 mass% NaAlSi3O8, the critical composition at 750°C obtained from the HDAC experiments. The corresponding critical pressure was 1.56GPa, as determined directly using zircon as Raman spectroscopic pressure sensor. Pressures at the melt-fluid homogenization temperature and along six isochoric P–T paths obtained from the Raman spectrum of zircon were close to or slightly lower than the pressure calculated from the EoS of H2O based on the vapor dissolution or ice melting temperature, which demonstrates that the effect of albite or NaAlSi3O8 melt dissolution is small. In an experiment up to 700°C and 2.28GPa, no clear evidence was found from optical observation for the hypothetical reappearance of melt-fluid immiscibility at higher pressure.The results consistently point to incongruent behavior at elevated pressures by the formation of paragonite. The HDAC experiments showed that paragonite nucleation was generally sluggish and occurred usually within several hours to days. For the critical composition of 40 mass% NaAlSi3O8, the temperature limit of paragonite stability was determined to a pressure of 1.2GPa using CSPVs and a PC and found to increase significantly with pressure. There was no discernible difference in its P–T location from that of the paragonite breakdown reaction to corundum, albite, and water reported in the literature for pressures to 0.7GPa. The paragonite stability limit intersected the critical curve at 764°C, 1.53GPa. Hence, our experiments indicate the existence of three previously not recognized stability fields in pseudosections for bulk compositions near 40 mass% NaAlSi3O8, namely (1) paragonite+albite+fluid, (2) paragonite+melt+fluid, and (3) paragonite+fluid. Formation of a substantial fraction of paragonite at these NaAlSi3O8 concentrations implies that the aqueous fluid must have a peralkaline composition, which has important implications for mass transfer in the crust an upper mantle, e.g. enhancement of the solubility of high field strength elements.

G.S. Henderson and D.R. Baker (Eds) Synchrotron Radiation: Earth, Environmental and Materials Sciences Applications. Mineralogical Association of Canada: Short Course Series, Volume 30, 2002, iv + 178 pp. Price $(Can) 40.00. ISBN 0-902-585-1816.

G.S. Henderson and D.R. Baker (Eds) Synchrotron Radiation: Earth, Environmental and Materials Sciences Applications. Mineralogical Association of Canada: Short Course Series, Volume 30, 2002, iv + 178 pp. Price $(Can) 40.00. ISBN 0-902-585-1816. - Volume 66 Issue 6

Salts of aliphatic carboxylic acids: Raman spectra and ion pairing in hydrothermal solutions containing sodium and calcium acetates

A 2.0 molal solution of sodium acetate and 0.1, 0.5, and 1.0 molal solutions of calcium acetate were investigated by Raman spectroscopy from 22 to 400°C at 1000 and 2000 bar. Experiments were performed in a special hydrothermal pressure vessel fitted with conical diamond windows. In the case of the sodium acetate solution, perturbations of the internal vibrational modes of the acetate ligand resulting from the formation of sodium acetate ion pairs were undetectable. In the case of calcium acetate, however, the OCO bending mode, the C–C symmetric stretching mode, and the C–O symmetric stretching mode all showed evidence of ion pairing between calcium and acetate. The degree of formation of the ion pairs increased with increasing temperature, increasing concentration, and decreasing pressure. Mass action constants were calculated for the reaction involving Ca 2+, CH 3COO −, and CaCH 3COO + which compare favorably with theoretically derived constants and with values derived from solubility experiments. The solutions existed metastably until temperatures approaching 480°C at which the acetate ligands underwent decarboxylation resulting in the formation of bicarbonate and methane. Combining mass action constants derived from this study with constants derived from the literature, distributions of the aqueous species were computed for the experimental conditions of the spectral measurements.

Raman spectra of potassium carbonate and bicarbonate aqueous fluids at elevated temperatures and pressures: comparison with theoretical simulations

One-molal solutions of potassium carbonate and potassium bicarbonate were investigated by Raman spectroscopy from 22° to 550°C and from 1000 to 2000 bar. Experiments were performed in a special hydrothermal pressure vessel fitted with conical diamond windows. Frequencies and half-widths of the vibrational modes were measured for both carbonate and bicarbonate as a function of temperature and pressure. In the case of potassium carbonate solutions, dissolved bicarbonate appeared with its concentration dramatically increasing with increasing temperature and decreasing density. The opposite behavior occurred in the case of potassium bicarbonate: the relative concentration of dissolved carbonate increased relative to total bicarbonate. In addition, at temperatures above 300°C, dissolved aqueous carbon dioxide appeared with its concentration continuing to increase with increasing temperature and decreasing density. Simulations using theoretically-predicted mass action constants were used to compute changes in solution speciation for these solutions as they were subjected to increased temperature and pressure. Results resulting from these predictions matched those discovered in the spectral measurements.

Complexing in Calcium Acetate and Propanoate Fluids at Elevated Temperatures and Pressures

The presence of saturated aliphatic carboxylic acids in low to medium temperature hydrothermal environments has been well documented. Experimental studies have demonstrated that acetic acid exists metastably to temperatures well above 300~ before undergoing decarboxylation (Palmer and Drummond, 1986). Similar expectations exist for propanoic and butanoic acids. Significant concentrations of acetic and propanoic acids have been measured in oil-field brines (Shock, 1994). Of particular interest has been the association of organic material with ore deposits such as the Mississippi Valley type. This has stimulated investigation of stability relations of metalic-organic complexes at elevated temperatures and pressures as such complexes may serve as major agents for the dissolution, transport and precipitation of the metals. Spectroscopic investigations of sodium and calcium acetate and propanoate solutions have been undertaken in order to investigate their relative stabilities and complexing behaviour as a function of temperature and pressure. Using a special hydrothermal pressure vessel fitted with conical diamond windows, Raman spectra of the acetate and propanoate solutions were measured at

The compositional limits of fluid immiscibility in the system H 2ONaClCO 2 as determined with the use of synthetic fluid inclusions in conjunction with mass spectrometry

The compositional limits of fluid immiscibility in the system NaClH 2OCO 2 were investigated from 500° to 700°C at pressures of 1, 2 and 3 kbar. Synthetic fluid inclusions formed in quartz prisms were equilibrated with high-temperature, high-pressure fluids in hydrothermal pressure vessels. The inclusions were analyzed optically, by mass spectrometry, and by microthermometry. The fields of immiscibility were defined as a function of temperature and pressure. Mass spectrometry was used to validate the existence of the immiscible fluids and to determine the CO 2 H 2 O ratios of the two coexisting phases. Microthermometry, i.e. the measurement of the melting temperature of solid sodium chloride, was used in conjunction with the results of the mass spectrometry measurements to define the tie-lines within the two-phase fields. Isochores and the location of a portion of the isopleth were determined for composition NaCl 8.9H 2O 76.1CO 2 15.0.

The solubility of noble gases in crude oil at 25–100°C

The solubility of the noble gases He, Ne, Ar, Kr and Xe was measured in two typical crude oils at temperatures of 25–100°C. The oil samples were obtained from the Elk Hills oil field located in southern San Joaquin Valley, California. The experimental procedure consisted of placing a known amount of gas with a known volume of crude oil in a stainless steel hydrothermal pressure vessel. The vessel was housed inside an oven and the entire unit rotates providing continuous mixing. The amount of gas dissolved in oil at a measured temperature and partial pressure of gas was used to calculate the solubility constants for these gases. Results show that the solubility of He and Ne in both oils is approximately the same; solubility then increases with atomic mass, with the solubility of Xe at 25°C being two orders of magnitude higher than that of He. The gas solubilities are somewhat higher in the lower density (higher API gravity) oil. The solubility of Ar is approximately constant in the range of temperatures of this study. The solubilities of He and Ne increase, but those of Kr and Xe decrease with increasing temperatures. Solubilities of noble gases in crude oil are significantly higher than their solubilities in water. For example, the solubilities of He and Xe at 25°C in the light oil of this study are, respectively, 3 and 24 times higher than their solubilities in pure water, and they are 15 and 300 times higher than in a brine with a salinity of 350,000 mg/l dissolved solids. These large and variable differences in the solubilities of noble gases in oil and water indicate that, in sedimentary basins with oil, these gases must be partitioned between oil, water and natural gas before they are used to deduce the origin and residence time of these fluids.

The nature of dissolved water in sodium silicate glasses and its effect on various properties

Sodium silicate glasses with a wide range of water contents were prepared. For water contents up to twelve wt% the specimens were prepared by melting Na 2 O·3 SiO 2 glass and varied amounts of water in hydrothermal pressure vessels. A few higher water content samples were synthesized by hydrating glasses in an autoclave under a steam atmosphere. The concentration of different species of water was analyzed by infrared spectroscopy. Density refractive index and the induced absorption due to γ-irradiation were analyzed in terms of the different water species present in the glasses. It has been observed that the effect of water on all these properties can be explained in terms of the different contributions of hydroxyls and molecular water.

Temperature measurement and distribution in Tuttle hydrothermal pressure vessels

The temperature of an experiment performed in a Tuttle hydrothermal pressure vessel may be subject to error from two sources (thermocouple error and thermocouple location error) and uncertainties from five sources (uncertainties in the previous two errors, temperature fluctuations, temperature gradients and pressure effects). The evaluation of each of these effects is discussed. The narrowest limits of accuracy which may be achieved with this apparatus in routine use is +or-3 degrees C. Two definitions in which the limits of accuracy of a measured temperature are taken as the sums of the uncertainties from all sources are proposed to describe the meaning of quoted temperatures in phase equilibrium work.

Hydrothermal Pressure Vessel Assembly for the Measurement of Pressure Generated by Corrosive Solutions

Hydrothermal Pressure Vessel Assembly for the Measurement of Pressure Generated by Corrosive Solutions

Experimental studies of anthracite coals at high pressures and temperatures

Three samples of anthracite, Middle Mammoth, Lykens Valley, and St. Nicholas have been subjected to temperatures in the range of 400-900 degrees C and pressures of 2,000 to 20,000 psi in hydrothermal pressure vessels. Selected runs were taken to 30 Kb in an opposed anvil device.The altered materials were studied primarily to determine differences in morphology of the grains, their reflectance values and degree of anisotropy. X-ray diffraction analyses were run to determine the mineral assemblages present before and after treatment.The reflectance values of the altered materials increase with temperature while pressure alone appears to have little effect. When temperature and pressure are held constant, reflectance increases with increasing time of the experimental runs. The rate of increase of reflectance is greatest in the temperature range where evolution of volatile matter is also the greatest. As might be expected the highest coal showed the least change in reflectance under the conditions applied.It was possible to fuse the anthracite particles with temperatures and pressures as low as 400 degrees C and 2,000 psi. Increased retention time at constant temperature and pressure causes an increase in the degree to which the grains are fused. The extreme temperature and pressure conditions to which the anthracites were subjected have caused them to behave in a fashion similar to bituminous coals at much lower pressures and somewhat lower temperatures.Observations made during this investigation correlate with existing theories on coal metamorphosis, pyrolysis and structure, extended from lower rank coals.