title: Mg and Ca isotope fractionation during CaCO3 biomineralisation.
abstract: The natural variation of Mg and Ca stable isotopes of carbonates has been determined in carbonate skeletons of perforate foraminifera and reef coral together with Mg/Ca ratios to assess the influence of biomineralisation processes. The results for coral aragonite suggest its formation, in terms of stable isotope behaviour, approximates to inorganic precipitation from a seawater reservoir. In contrast, results for foraminifera calcite suggest a marked biological control on Mg isotope ratios presumably related to its low Mg content compared with seawater. The bearing of these observations on the use of Mg and Ca isotopes as proxies in paleoceanography is considered.
authors.affiliation: Department of Earth Sciences, University of Oxford, Parks Road, Oxford OX1 3PR, UK. bob.williams@chem.ox.ac.uk
authors.forename: Veronica T-C
authors.initials: VT
authors.lastname: Chang
authors.forename: R J P
authors.initials: RJ
authors.lastname: Williams
authors.forename: Akio
authors.initials: A
authors.lastname: Makishima
authors.forename: Nick S
authors.initials: NS
authors.lastname: Belshawl
authors.forename: R Keith
authors.initials: RK
authors.lastname: O'Nions
mesh_terms: D000818:Animals; D037421:Anthozoa; D002118:Calcium / Q000737:chemistry*; D002119:Calcium Carbonate / Q000737:chemistry*; D002127:Calcium Isotopes / Q000737:chemistry*; D004305:Dose-Response Relationship, Drug; D007554:Isotopes; D008274:Magnesium / Q000737:chemistry*; D012623:Seawater; D013696:Temperature
chemical_list: D002127:Calcium Isotopes; D007554:Isotopes; D002119:Calcium Carbonate; D008274:Magnesium; D002118:Calcium