In situ δ7Li, Li/Ca, and Mg/Ca analyses of synthetic aragonites
Gabitov, R. I.
Schmitt, A. K.
McKeegan, K. D.
Gaetani, Glenn A.
Cohen, Anne L.
Watson, E. B.
Harrison, T. M.
MetadataShow full item record
In situ secondary ion mass spectrometry (SIMS) analyses of δ7Li, Li/Ca, and Mg/Ca were performed on five synthetic aragonite samples precipitated from seawater at 25°C at different rates. The compositions of δ7Li in bulk aragonites and experimental fluids were measured by multicollector inductively coupled plasma–mass spectrometry (MC-ICP-MS). Both techniques yielded similar δ7Li in aragonite when SIMS analyses were corrected to calcium carbonate reference materials. Fractionation factors α7Li/6Li range from 0.9895 to 0.9923, which translates to a fractionation between aragonite and fluid from −10.5‰ to −7.7‰. The within-sample δ7Li range determined by SIMS is up to 27‰, exceeding the difference between bulk δ7Li analyses of different aragonite precipitates. Moreover, the centers of aragonite hemispherical bundles (spherulites) are enriched in Li/Ca and Mg/Ca relative to spherulite fibers by up to factors of 2 and 8, respectively. The Li/Ca and Mg/Ca ratios of spherulite fibers increase with aragonite precipitation rate. These results suggest that precipitation rate is a potentially important consideration when using Li isotopes and elemental ratios in natural carbonates as a proxy for seawater composition and temperature.
Author Posting. © American Geophysical Union, 2011. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 12 (2011): Q03001, doi:10.1029/2010GC003322.
Showing items related by title, author, creator and subject.
Temperature and carbonate ion effects on Mg/Ca and Sr/Ca ratios in benthic foraminifera : aragonitic species Hoeglundina elegans Rosenthal, Yair; Lear, Caroline H.; Oppo, Delia W.; Linsley, Braddock K. (American Geophysical Union, 2006-02-21)Core top samples from Atlantic (Little Bahama Banks (LBB)) and Pacific (Hawaii and Indonesia) depth transects have been analyzed in order to assess the influence of bottom water temperature (BWT) and aragonite saturation ...
Variations in coral reef net community calcification and aragonite saturation state on local and global scales Bernstein, Whitney N. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2013-09)Predicting the response of net community calcification (NCC) to ocean acidification (OA) and declining aragonite saturation state (Ωa) requires a thorough understanding of controls on NCC. The diurnal control of light ...
Neodymium isotope analyses after combined extraction of actinide and lanthanide elements from seawater and deep-sea coral aragonite Struve, Torben; van de Flierdt, Tina; Robinson, Laura F.; Bradtmiller, Louisa I.; Hines, Sophia K.; Adkins, Jess F.; Lambelet, Myriam; Crocket, Kirsty C.; Kreissig, Katharina; Coles, Barry; Auro, Maureen E. (John Wiley & Sons, 2016-01-09)Isotopes of the actinide elements protactinium (Pa), thorium (Th), and uranium (U), and the lanthanide element neodymium (Nd) are often used as complementary tracers of modern and past oceanic processes. The extraction of ...