Rare earth elements, Sr, Ba, Fe, and major cation concentrations in some living foraminiferal tests collected from Iriomote Island, Japan: An exploration for trace element behavior during biogenic calcium carbonate formation

Abstract

Rare earth elements (REE), Sr, Ba, Fe, Mg, Ca, Na, and K concentrations in three kinds of living foraminiferal tests collected from Iriomote Island, Japan were measured in order to obtain some qualitative aspects of trace element behavior during biogenic CaCO 3 formation. The obtained results were examined using the sample/seawater concentration ratios, which can be considered as a measure of total effect of element incorporation into biogenic CaCO 3 in marine environments. On a sample/seawater concentration ratio vs. ionic radius diagram, the foraminifera/seawater ratios of trivalent REEs and divalent Mg, Ca and Sr fall on their respective curves having peaks near the Ca ionic radius. This is consistent with the most widely accepted theory that solid/liquid partition coefficients are largely controlled by the sizes of the host site in the crystal and the substituting cation, such that a cation that has the most suitable size for the site can enter the crystal most easily. On the other hand, the foraminifera/seawater ratios of Fe and Ba show higher values than those expected from the crystal structure control model, which might be caused by insoluble precipitates such as Fe-hydroxides and barite. It is interesting that the concentrations of REEs in foraminifera are correlated with those of Fe, which suggests coprecipitation of REE with Fe-hydroxide. Such coprecipitation of REE might have occurred in seawater, followed by uptake of Fe-hydroxides by foraminiferal food micro-organisms. After digestion of such food, the dissolved REEs in intracellular fluid might have fractionated as CaCO 3 crystallization proceeds, and the combined crystal structure and ionic radius effect becomes conspicuous forming a peak on the foraminifera/seawater ratio vs. ionic radius diagram.

Variation in the diagenetic response of aragonite archives to hydrothermal alteration

“…Higher rates of carbonate precipitation can also lead to deviations from equilibrium conditions, and result in higher or lower amounts of foreign ion incorporation during formation if the partitioning coefficient of the respective ion between solid and fluid (D M ) is below or above unity, respectively (Amiel et al, 1973;Dietzel et al, 2004;Böttcher and Dietzel, 2010;Rollion-Bard and Blamart, 2015;Jamieson et al, 2016;Mavromatis et al, 2018). Some (e.g., Smith et al, 1979;Dietzel et al, 2004) have also documented (aragonitic) biogenic samples to generally have lower D Sr values (less Sr incorporation) compared to inorganic precipitates, likely due to the ability of organisms to exhibit control over their skeleton chemistry (Lowenstam, 1964;Weber, 1973;de Villers et al, 1995;Meibom et al, 2004;Terakado et al, 2010). Furthermore, due to the relatively high concentrations of Mg 2+ (0.0526 mol/kg) and SO 4 2-(0.0279 mol/kg) in seawater compared to Sr 2+ (0.00009 mol/kg) (Duxbury et al, 2018), the incorporation of these substitution ions are likely higher in carbonates formed in marine and hypersaline environments.…”

Impact of salinity on element incorporation in two benthic foraminiferal species with contrasting magnesium contents

“…For example, Mg / Ca cc values are different between groups of low-Mg, high-Mg hyaline and porcelaneous foraminifera (Toyofuku et al, 2000;Segev and Erez, 2006;Raja et al, 2007), which also seems to be reflected in other co-precipitated cations (De Nooijer et al, 2017). Hence, calibration of Na / Ca cc as a function of salinity for other species is not only necessary to test the applicability of this novel proxy for other groups of foraminifera but also allows testing whether monovalent cations follow the inter-species trends described for divalent cations (Terakado et al, 2010).…”

Impact of salinity on element incorporation in two benthic foraminiferal species with contrasting Magnesium contents

“…of Na/Cacc as a function of salinity for other species is not only necessary to test the applicability of this 68 novel proxy for other groups of foraminifera, but also allows testing whether monovalent cations 69 follow the inter-species trends described for divalent cations (Terakado et al, 2010). 70…”