Köhler, Stephan
- Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
Abstract
In order to apply Sr/Ca and Ca-44/Ca-40 fractionation during calcium carbonate (CaCO3) formation as a proxy to reconstruct paleo-environments, it is essential to evaluate the impact of various environmental factors. In this study, a CO2 diffusion technique was used to crystallize inorganic calcite from aqueous solutions at different ionic strength/salinity by the addition of NaCl at 25 degrees C. Results show that the discrimination of Sr2+ versus Ca2+ during calcite formation is mainly controlled by precipitation rate (R in mu mol/m(2)/h) and is weakly influenced by ionic strength/salinity. In analogy to Sr incorporation, Ca-44/Ca-40 fractionation during precipitation of calcite is weakly influenced by ionic strength/salinity too. At 25 degrees C the calcium isotope fractionation between calcite and aqueous calcium ions (Delta Ca-44/40(calcite-aq) = delta Ca-44/40(calcite) = delta Ca-44/40(aq)) correlates inversely to log R values for all experiments. In addition, an inverse relationship between Delta Ca-44/40(calcite-aq) and log D-Sr, which is independent of temperature, precipitation rate, and aqueous (Sr/Ca)(aq) ratio, is not affected by ionic strength/salinity either. Considering the log D-Sr and Delta Ca-44/40(calcite-aq) relationship, Sr/Ca and delta Ca-44/40(calcite) values of precipitated calcite can be used as an excellent multi-proxy approach to reconstruct environmental conditions (e. g., temperature, precipitation rate) of calcite growth and diagenetic alteration. (C) 2011 Elsevier Ltd. All rights reserved.
Published in
Geochimica et Cosmochimica Acta
2012, volume: 77, pages: 432-443
Publisher: PERGAMON-ELSEVIER SCIENCE LTD
SLU Authors
UKÄ Subject classification
Analytical Chemistry
Publication identifier
- DOI: https://doi.org/10.1016/j.gca.2011.10.039
Permanent link to this page (URI)
https://res.slu.se/id/publ/89835