Temperature and salinity effects on ~18O fractionation for rapidly precipitated carobnates: Laboratory experiments with alkaline lake water --Perspective

摘要

An important factor involved in determining the isotopic composition of precipitating lake minerals is their min- eralogy. In the Dead Sea (Israel) the aragonite-calcite ratio of lake carbonate sediments can be correlated with δ~13C and δ~18O fractionation. Increasing aragonite con- centration conforms to an increase in the heavier car- bon and oxygen isotopes. The enrichment of the heavier istopoes is explained by strong evaporation during the formation of aragonite, when the lighter isotopes are preferentially removed as part of Co_2. Calcite was formed as a result of degradation of gypsum through the activity of bacteria which preferentially use lighter iso- topes form their carbon source.