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Calcium Isotopic Composition of Various Reference Materials and Seawater
Author(s) -
Hippler Dorothee,
Schmitt AnneDésirée,
Gussone Nikolaus,
Heuser Alexander,
Stille Peter,
Eisenhauer Anton,
Nägler Thomas F.
Publication year - 2003
Publication title -
geostandards newsletter
Language(s) - English
Resource type - Journals
eISSN - 1751-908X
pISSN - 0150-5505
DOI - 10.1111/j.1751-908x.2003.tb00709.x
Subject(s) - nist , seawater , mineralogy , calcium , isotope , isotopes of calcium , chemistry , analytical chemistry (journal) , environmental chemistry , geology , oceanography , computer science , physics , organic chemistry , quantum mechanics , natural language processing
A compilation of δ 44/40 Ca (δ 44/40 Ca) data sets of different calcium reference materials is presented, based on measurements in three different laboratories (Institute of Geological Sciences, Bern; Centre de Géochimie de la Surface, Strasbourg; GEOMAR, Kiel) to support the establishment of a calcium isotope reference standard. Samples include a series of international and internal Ca reference materials, including NIST SRM 915a, seawater, two calcium carbonates and a CaF 2 reference sample. The deviations in δ 44/40 Ca for selected pairs of reference samples have been defined and are consistent within statistical uncertainties in all three laboratories. Emphasis has been placed on characterising both NIST SRM 915a as an internationally available high purity Ca reference sample and seawater as representative of an important and widely available geological reservoir. The difference between δ 44/40 Ca of NIST SRM 915a and seawater is defined as ‐1.88 O.O4%o (δ 44/42 Ca NISTSRM915a/Sw = ‐0.94 0.07%o). The conversion of values referenced to NIST SRM 915a to seawater can be described by the simplified equation δ 44/40 Ca Sa/Sw =δ 44/40 Ca Sa/NIST SRM 915a ‐ 1.88 (δ 44/42 Ca Sa/Sw =δ 44/42 Ca Sa/NIST SRM 915a ‐ 0.94). We propose the use of NIST SRM 915a as general Ca isotope reference standard, with seawater being defined as the major reservoir with respect to oceanographic studies.