Open AccessPreferential dissolution of benthic foraminiferal calcite during laboratory reductive cleaning
Author(s) -
Yu Jimin,
Elderfield Henry,
Greaves Mervyn,
Day Jason
Publication year - 2007
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2006gc001571
Subject(s) - calcite , dissolution , foraminifera , reagent , leaching (pedology) , trace element , benthic zone , chemistry , mineralogy , environmental chemistry , geology , geochemistry , oceanography , soil science , soil water
We have investigated the effect of cleaning procedures on eight element/Ca ratios in three widely used benthic foraminifera species from core top and down core sediments. Two cleaning techniques were employed: (1) comparison between “Mg‐cleaning” and “Cd‐cleaning” methods and (2) comparison between the various constituent reagents. Li/Ca, B/Ca, and Sr/Ca ratios remained unchanged for samples subjected to different treatments, but Mg/Ca, Mn/Ca, Zn/Ca, Cd/Ca, and U/Ca were substantially decreased when foraminifera shells were cleaned with reagents containing citrate. In contrast, no significant decreases in element/Ca ratios were observed for samples cleaned in N 2 H 4 without citrate, indicating that the role of N 2 H 4 was insignificant during reductive cleaning and that citrate is responsible for decreases of Mg/Ca, Mn/Ca, Zn/Ca, Cd/Ca, and U/Ca. Decreases in these ratios are most likely due to (1) removal of contaminant particles enriched in Mg, Mn, Zn, Cd and U and/or (2) preferential leaching of CaCO 3 by the formation of stable metal complexes through chelation between citrate and metals heterogeneously distributed in foraminiferal shells. Due to the negligible effect of N 2 H 4 and preferential dissolution of CaCO 3 during reductive cleaning, it is suggested that the reductive cleaning step should be omitted and the “Mg‐cleaning” method [ Barker et al. , 2003] could be employed to clean foraminiferal shells for trace element measurements.