Calcium Isotope Materials
Terrestrial isotopic-abundance variations for calcium are largest for biological systems, whereas inorganic materials exhibit only small calcium isotopic fractionations. Calcium-40 may be a poor choice for the denominator in the isotope ratio measurements because 40Ca is a product of 40K radioactive decay.
|NIST SRM 915a||CaCO3||0 ‰*|
|NIST SRM 915||CaCO3||+0.085 ‰ **|
|USGS EN-1||shell from marine organism||+0.35(9) ‰|
* Exact value defining the δ44/42CaSRM915a scale.
** See the Assessment of international reference materials for isotope-ratio analysis for more details.
Values in parenthesis are expanded (k = 2) uncertainties applicable to the last digits. The values listed in this table are compilation and are not necessarily CIAAW recommendations.