Calcium isotope constraints on the uptake and sources of Ca2+ in a base-poor forest: A new concept of combining stable (δ44/42Ca) and radiogenic (εCa) signals

Calcium isotopic ratios and rare earth element abundances in refractory inclusions from the Allende CV3 chondrite

“…The 42 Ca/ 44 Canormalization was chosen because, in general, there are no nucleosynthetic isotopic anomalies on 42 Ca or 44 Ca (e.g., Jungck et al, 1984;Niederer and Papanastassiou, 1984;Simon et al, 2009;Lee et al, 2011). Note, however, that Chen et al (2011) recently reported an example of nucleosynthetic isotopic anomalies on 42 …”

“…We use mass-independent Ca isotopic effects to measure the nucleosynthetic isotopic anomalies in extraterrestrial materials, such as refractory inclusions and chondrites (e.g., Simon et al, 2009;Chen et al, 2011;Lee et al, 2011). In this case, the 40 Ca/ 44 Ca, 43 Ca/ 44 Ca and 48 Ca/ 44 Ca ratios of the samples and the standard are internally normalized (indicated by N) to 42 Ca/ 44 Ca = 0.31221 (Russell et al, 1978) using an exponential law to correct for both instrumental fractionation and fractionation intrinsic to the sample. The data are reported using the e notation (e 40/44 Ca, e 43/44 Ca and e 48/44 Ca) relative to the isotopic ratios (after internal normalization to 42 …”

“…After internal normalization to 42 Ca/ 44 Ca of 0.31221 (Russell et al, 1978), 18 measurements of NIST SRM 915a yield 40 Ca/ 44 Ca of 47.134 ± 0.002 (2r m ), 43 Ca/ 44 Ca of 0.064946 ± 0.000005 (2r m ) and 48 Ca/ 44 Ca of 0.088689 ± 0.000006 (2r m ). 46 Ca was not determined in this study because of its low abundance.…”

“…(1)-(3)) were determined by a 43 Ca-48 Ca double spiking technique using an offline data reduction procedure with an exponential law (Russell et al, 1978;Heuser et al, 2002;Farkaš et al, 2007aFarkaš et al, ,b, 2011Huang et al, 2010), an approach adopted from earlier Ba isotopic measurements of meteorites (Eugster et al, 1969). The 43 Ca-48 Ca double spike solution used in this study was prepared from isotopically enriched carbonates, Ca43-NX and Ca48-RT, from Oak Ridge National Laboratory, as described in the Appendix of Huang et al (2010).…”

“…The combined unspiked and spiked analyses of NIST SRM 915a yield 40 Ca/ 44 Ca of 46.406 ± 0.001 (2r m ), 42 Ca/ 44 Ca of 0.30985 ± 0.00001 (2r m ), 43 Ca/ 44 Ca of 0.064703 ± 0.000006 (2r m ) and 48 Ca/ 44 Ca of 0.089958 ± 0.000006 (2r m ). Note that, these values are different from those obtained by unspiked measurements in which an internal normalization to 42 Ca/ 44 Ca of 0.31221 was applied. These values, obtained using both spiked and unspiked measurements, are not absolute isotopic compositions either, because the isotopic composition of our 43 Ca-48 Ca double spike contains uncorrected instrumental fractionation.…”