The isotope composition of evaporating brines: Effect of the isotopic activity ratio in saline solutions

Z. Sofer; J. R. Gat

doi:10.1016/0012-821X(75)90085-0

The isotope composition of evaporating brines: Effect of the isotopic activity ratio in saline solutions

Z. Sofer, J. R. Gat

Research output: Contribution to journal › Article › peer-review

191 Scopus citations

Abstract

The ratio of the activity coefficients of deuterated and light water (Γ) is given in chloridic saline solutions as a function of the molality of the salt components by the expression: 1- 1 Γ × 10³ -δγ = 6.1M_CaCl₂ + 5.1M_MgCl₂ + 2.4M_KCl + 0.4M_NaCl. Calculations based on the Craig-Gordon evaporation model show that in the case of evaporating brines, the salt effect on the activity coefficients of the isotopic water species results in deviation of the δ values from a constant slope "evaporation line", when plotted on the conventional δ-diagram, of deuterium concentration versus ¹⁸O activity. Conversion of concentration data to activities eliminates these deviations to a large extent, indicating them to be an artifact of the scales employed for measuring the isotope abundance. The origin of Dead Sea waters and other natural brines is discussed in the light of these findings.

Original language	English
Pages (from-to)	179-186
Number of pages	8
Journal	Earth and Planetary Science Letters
Volume	26
Issue number	2
DOIs	https://doi.org/10.1016/0012-821X(75)90085-0
State	Published - 1 Jan 1975
Externally published	Yes

ASJC Scopus subject areas

Geophysics
Geochemistry and Petrology
Space and Planetary Science
Earth and Planetary Sciences (miscellaneous)

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10.1016/0012-821X(75)90085-0

Cite this

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title = "The isotope composition of evaporating brines: Effect of the isotopic activity ratio in saline solutions",

abstract = "The ratio of the activity coefficients of deuterated and light water (Γ) is given in chloridic saline solutions as a function of the molality of the salt components by the expression: 1- 1 Γ × 103 -δγ = 6.1MCaCl2 + 5.1MMgCl2 + 2.4MKCl + 0.4MNaCl. Calculations based on the Craig-Gordon evaporation model show that in the case of evaporating brines, the salt effect on the activity coefficients of the isotopic water species results in deviation of the δ values from a constant slope {"}evaporation line{"}, when plotted on the conventional δ-diagram, of deuterium concentration versus 18O activity. Conversion of concentration data to activities eliminates these deviations to a large extent, indicating them to be an artifact of the scales employed for measuring the isotope abundance. The origin of Dead Sea waters and other natural brines is discussed in the light of these findings.",

author = "Z. Sofer and Gat, {J. R.}",

note = "Funding Information: Research supported in part by the Israel National Commission for Basic Research.",

year = "1975",

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doi = "10.1016/0012-821X(75)90085-0",

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T1 - The isotope composition of evaporating brines

T2 - Effect of the isotopic activity ratio in saline solutions

AU - Sofer, Z.

AU - Gat, J. R.

N1 - Funding Information: Research supported in part by the Israel National Commission for Basic Research.

PY - 1975/1/1

Y1 - 1975/1/1

N2 - The ratio of the activity coefficients of deuterated and light water (Γ) is given in chloridic saline solutions as a function of the molality of the salt components by the expression: 1- 1 Γ × 103 -δγ = 6.1MCaCl2 + 5.1MMgCl2 + 2.4MKCl + 0.4MNaCl. Calculations based on the Craig-Gordon evaporation model show that in the case of evaporating brines, the salt effect on the activity coefficients of the isotopic water species results in deviation of the δ values from a constant slope "evaporation line", when plotted on the conventional δ-diagram, of deuterium concentration versus 18O activity. Conversion of concentration data to activities eliminates these deviations to a large extent, indicating them to be an artifact of the scales employed for measuring the isotope abundance. The origin of Dead Sea waters and other natural brines is discussed in the light of these findings.

AB - The ratio of the activity coefficients of deuterated and light water (Γ) is given in chloridic saline solutions as a function of the molality of the salt components by the expression: 1- 1 Γ × 103 -δγ = 6.1MCaCl2 + 5.1MMgCl2 + 2.4MKCl + 0.4MNaCl. Calculations based on the Craig-Gordon evaporation model show that in the case of evaporating brines, the salt effect on the activity coefficients of the isotopic water species results in deviation of the δ values from a constant slope "evaporation line", when plotted on the conventional δ-diagram, of deuterium concentration versus 18O activity. Conversion of concentration data to activities eliminates these deviations to a large extent, indicating them to be an artifact of the scales employed for measuring the isotope abundance. The origin of Dead Sea waters and other natural brines is discussed in the light of these findings.

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JO - Earth and Planetary Science Letters

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The isotope composition of evaporating brines: Effect of the isotopic activity ratio in saline solutions

Abstract

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