Helium in solubility equilibrium with quartz and porefluids in rocks - a new approach in hydrology

Quartz crystals in sandstones at depths of 1200 m–1400 m below the surface appear to reach a solubility equilibrium with the 4He-concentration in the surrounding pore- or groundwater after some time. A rather high 4Heconcentration of 4.5x10E-3 cc STP 4He/cm3 of water measured in a groundwater sample would for instance maintain a He pressure of 0.47 atm in a related volume. This value is equal within analytical error to the pressure deduced from the measured helium content of the quartz and its internal helium-accessible volume. To determine this volume, quartz crystals of 0.1 to 1 mm were separated from sandstones and exposed to a helium gas pressure of 32 atm at a temperature of 290°C for up to 2 months. By crushing, melting or isothermal heating the helium was then extracted from the helium saturated samples. Avolume on the order of 0.1% of the crystal volume is only accessible to helium atoms but not to argon atoms or water molecules. By monitoring the diffusive loss of He from the crystals at 350°C an effective diffusion constant on the order of 10E-9 cm2/s is estimated. Extrapolation to the temperature of 70°C in the sediments at a depth of 1400 m gives a typical time of about 100 000 years to reach equilibrium between helium in porewaters and the internal He-accessible volume of quartz crystals. In a geologic situation with stagnant pore- or groundwaters in sediments it therefore appears to be possible with this new method to deduce a 4He depth profile for porewaters in impermeable rocks based on their mineral record.

Barium isotope fractionation during witherite (BaCO3) dissolution, precipitation and at equilibrium

This study examines the behavior of Ba isotope fractionation between witherite and fluid during mineral dissolution, precipitation and at chemical equilibrium. Experiments were performed in batch reactors at 25 oC in 10-2 M NaCl solution where the pH was adjusted by continuous bubbling of a water saturated gas phase of CO2 or atmospheric air. During witherite dissolution no Ba isotope fractionation was observed between solid and fluid. In contrast, during witherite precipitation, caused by a pH increase, a preferential uptake of the lighter 134Ba isotopomer in the solid phase was observed. In this case, the isotope fractionation factor αwitherite-fluid is calculated to be 0.99993 ± 0.00004 (or Δ137/134Bawitherite-fluid ≈ -0.07 ± 0.04 ‰, 2sd). The most interesting feature of this study, however, is that after the attainment of chemical equilibrium, the Ba isotope composition of the aqueous phase is progressively becoming lighter, indicating a continuous exchange of Ba2+ ions between witherite and fluid. Mass balance calculations indicate that the detachment of Ba from the solid is not only restricted to the outer surface layer of the solid, but affects several (~7 unit cells) subsurface layers of the crystal. This observation comes in excellent agreement with the concept of a dynamic system at chemical equilibrium in a mineral-fluid system, denoting that the time required for the achievement of isotopic equilibrium in the witherite-fluid system is longer compared to that observed for chemical equilibrium. Overall, these results indicate that the isotopic composition of Ba bearing carbonates in natural environments may be altered due to changes in fluid composition without a net dissolution/precipitation to be observed.

Rolling resistance of tires measured under transient and equilibrium conditions on Calspan's tire research. Final report.

Transportation Department, Office of the Assistant Secretary for Systems Development and Technology, Washington, D.C.

Aqueous ammonia equilibrium : tabulation of percent un-ionized ammonia /

Mode of access: Internet.

REDEQL.EPAK : aqueous chemical equilibrium computer program /

"Marine Division, Corvallis Environmental Research Laboratory."

The equilibrium between carbon oxysulfide, carbon monoxide and sulfur ...

Thesis t.-p. pasted over the cover of the issue reprinted from the Journal of the American chemical society, vol. XXXVII, no. 9, September, 1915, which has title: The equilibrium between carbon oxysulfide, carbon monoxide and sulfur, by Gilbert N. Lewis and William N. Lacey.

The structure of American economy, 1919-1929 : an empirical application of equilibrium analysis /

Bibliographical references in "Statistical sources and methods of computation" (p.[141]-162.)

Equilibrium and transient rolling resistance of truck tires measured on Calspan's tire research facility. Final report.

Transportation Department, Office of Noise Abatement, Washington, D.C.

Rolling resistance of truck tires as measured under equilibrium and transient conditions on Calspan's tire research facility. Final report.

Transportation Department, Office of Noise Abatement, Washington, D.C.

Equilibrium studies with certain acids and minerals and their probable relation to the decomposition of minerals by bacteria,

Published also as thesis (Ph.D) University of California, 1919.

Preliminary drilling at the Nash Car Area, White Canyon District, San Juan County, Utah /

"March 10, 1953."

I. The equilibrium in liquid mixtures of ammonia and xylene. II. The molecular weight of complex sodium tellurides in liquid ammonia,

Reprinted from articles by Charles A. Kraus and Edward H. Zeitfuchs in the Journal of the American Chemical Society, v. 44, no. 6, June, 1922 and v. 44, no. 12, December, 1922.

Molecular physics of equilibrium gases : a handbook for engineers /

Includes bibliographical references and index.