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Robert J. Rosenbauer

Publications and source records attributed to Robert J. Rosenbauer.

46 records · Page 3Linked to original sources
USGS1987

Pressure-composition relations for coexisting gases and liquids and the critical points in the system NaCl-H 2 O at 450, 475, and 500°C

Pressure-temperature-composition ( P , T , x ) relations for the co-existing vapor and liquid phases in the system NaCl-H 2 O were determined experimentally at 450, 475, and 500°C. Data for each isotherm include P - x relations near the critical point and extend to the three-phase assemblage vapor-liquid-halite on the vapor side. On the liquid side the P - x data range from the critical point to the room-temperature halite saturation point (~25 wt.% NaCl). Critical pressures were calculated from measured pressures and compositions and classical theory. The results generally support the few data points of Urusova (1974, 1975) and Ölander and Liander (1950) but differ markedly from the extensive data of Sourirajan and Kennedy (1962).

Geochimica et Cosmochimica Acta↗
USGS1987

Phase separation in seafloor geothermal systems: An experimental study of the effects on metal transport

Experimental investigations were carried out by reacting natural and evolved sea-water with crystalline basalt from the Juan de Fuca Ridge in order to study the effects of vapour-liquid phase separation on metal mobilization in sea-floor geothermal systems in which phase separation occurs between the top of a magma chamber (300-500 bar) and the sea-floor (230-250 bar). The geochemical processes produced by a combination of closed-system phase separation and adiabatic expansion under the conditions characterizing the sea-floor geothermal systems resulted in a significant increase in the acidity and concentration of heavy metals in the liquid phase and strikingly high concentrations of metals in the vapour.

American Journal of Science↗
USGS1985

Uranium-series dating of sediments from Searles Lake: Differences between continental and marine climate records

One of the major unresolved questions in Pleistocene paleoclimatology has been whether continental climatic transitions are consistent with the glacial δ 18 O marine record. Searles Lake in California, now a dry salt pan, is underlain by sediment layers deposited in a succession of lakes whose levels and salinities have fluctuated in response to changes in climate over the last 3 × 10 6 years. Uranium-series dates on the salt beds range from 35 × 10 3 to 231 × 10 3 years. This range of dates allows identification of lake-sediment horizons that are time correlatives of the boundaries of marine isotope stages from the recent 3/4 boundary back to the 8/9 boundary. The 5/6 boundary coincided with a deepening of the lake, but the analogous 1/2 boundary coincided with desiccation. The 3/4, 4/5, 6/7, 7/8, and 8/9 boundaries correspond in age to horizons that record little or no change in sedimentation or climate. These hydrologic results demonstrate that the continental paleoclimate record at this mid-latitude site does not mimic the marine record.

California↗
USGS1984

The critical point and two-phase boundary of seawater, 200–500°C

The two-phase boundary of seawater was determined by isothermal decompression of fully condensed seawater in the range of 200–500°C. The pressure at which phase separation occurred for each isotherm was determined by a comparison of the refractive index of fluid removed from the top and bottom of the reaction vessel. The critical point was determined to be in the range of 403–406°C, 285–302 bar and was located by the inflection in the two-phase boundary and by the relative volume of fluid and vapor as a function of temperature. The two-phase boundary of 3.2% NaCl solution was found to coincide exactly with that of seawater over the range tested in the present study. The boundary for both is described by a single seventh-order polynomial equation. The two-phase boundary defines the maximum temperature of seawater circulating at depth in the oceanic crust. Thus the boundary puts a limit of about 390°C for seawater circulating near the seafloor at active ocean ridges (2.5 km water depth), and about 465°C at the top of a magma chamber occurring at 2 km below the seafloor.

Earth and Planetary Science Letters↗
USGS1983

Uptake and transport of heavy metals by heated seawater: A summary of the experimental results

In general, the chemistry of seawater experimentally reacted with basalt is in accord with the observed chemistry of the 350°C vent waters from 21°N on the East Pacific Rise. Experiments at 350°C, 500 bar, and a water/rock ratio of ≤10 reproduce most of the major components in the vent waters, in particular the low Mg and SO 4 and high Si0 2 , Ca, and K. In comparison with the vent waters however the experimental fluids are deficient in H + and heavy metals. Experiments with natural and evolved seawater (Mg and SO 4 depleted) at ≥400 C and 500 bars or 375°C and ~375 bars under rock-dominated conditions more closely reproduce the vent-water chemistry.

Book chapter↗
USGS1983

A note on the chemistry of seawater in the range 350°-500°C

The chemistry of seawater at conditions of 350° to 500°C, 220 to 1000 bars (22 to 100 MPa) is controlled by reactions involving magnesium hydroxide sulfate (MHSH) and anhydrite. During progressive heating from 350° to 500°C at 1000 bars (100 MPa), MHSH with a ratio of 1.25 is formed via precipitation from solution and via reaction of solution with pre-existing anhydrite. During adiabatic expansion the MHSH extracts additional SO 4 from seawater and converts to a stoichiometry in which . These reactions control and greatly change the concentrations of Ca, Mg, SO 4 in solution and produce significant ionizable hydrogen, attaining 11.7 mmoles kg −1 at maximum conditions.

Geochimica et Cosmochimica Acta↗
USGS1982

The solubility of quartz in aqueous sodium chloride solution at 350°C and 180 to 500 bars

The solubility of quartz in 2, 3, and 4 molal NaCl was measured at 350°C and pressures ranging from 180 to 500 bars. The molal solubility in each of the salt solutions is greater than that in pure water throughout the measured pressure range, with the ratio of solubility in NaCl solution to solubility in pure water decreasing as pressure is increased. The measured solubilities are significantly higher than solubilities calculated using a simple model in which the water activity in NaCl solutions decreases either in proportion to decreasing vapor pressure of the solution as salinity is increased or in proportion to decreasing mole fraction of water in the solvent.

Geochimica et Cosmochimica Acta↗
USGS1981

Seawater sulfate reduction and sulfur isotope fractionation in basaltic systems: interaction of seawater with fayalite and magnetite at 200–350°C

Sulfate reduction during seawater reaction with fayalite and with magnetite was rapid at 350°C, producing equilibrium assemblages of talc-pyrite-hematite-magnetite at low water/rock ratios and talc-pyrite-hematite-anhydrite at higher water/rock ratios. At 250°C, seawater reacting with fayalite produced detectable amounts of dissolved H 2 S, but extent of reaction of solid phases was minor after 150 days. At 200°C, dissolved H 2 S was not detected, even after 219 days, but mass balance calculations suggest a small amount of pyrite may have formed. Reaction stoichiometry indicates that sulfate reduction requires large amounts of H + , which, in subseafloor hydrothermal systems is provided by Mg metasomatism. Seawater contains sufficient Mg to supply all the H + necessary for quantitative reduction of seawater sulfate. Systematics of sulfur isotopes in the 250 and 350°C experiments indicate that isotopic equilibrium is reached, and can be modeled as a Rayleigh distillation process. Isotopic composition of hydrothermally produced H 2 S in natural systems is strongly dependent upon the seawater/basalt ratio in the geothermal system, which controls the relative sulfide contributions from the two important sulfur sources, seawater sulfate and sulfide phases in basalt. Anhydrite precipitation during geothermal heating severely limits sulfate ingress into high temperature interaction zones. Quantitative sulfate reduction can thus be accomplished without producing strongly oxidized rocks and resultant sulfide sulfur isotope values represent a mixture of seawater and basaltic sulfur.

Geochimica et Cosmochimica Acta↗
USGS1981

Uranium-series and soil-geomorphic dating of the Calico archaeological site, California

Lithic specimens identified as artifacts have been recovered from near the base of the Yermo fan deposits at Calico, California. The soil on the fan surface is a strongly developed relict paleosol. Comparison of this soil with dated paleosols elsewhere in the southwestern United States suggests that the surface is about 80,000 to 125,000 yr old. Clasts near the base of the deposit are well cemented by laminated CaCO 3 that probably formed from groundwater action while the fan was still active. Uranium-thorium assays on the CaCO 3 indicate an age of 200,000 yr.

California↗