The calcium riverine and hydrothermal isotopic fluxes and the oceanic calcium mass balance

Calcium and magnesium isotope systematics in rivers draining the Himalaya-Tibetan-Plateau region: Lithological or fractionation control?

“…Data is from the present study, Schmitt et al (2003), Zhu and Macdougall (1998) and Tipper et al (2006a) for rivers, Fantle and DePaolo (2007), Fantle and DePaolo (2005) Mg and Ca isotope ratios in rivers are therefore controlled by both heterogeneity in source rock Ca and Mg isotope ratios, and fractionation of Ca and Mg isotope ratios during the transfer of Ca and Mg from rock to the dissolved load. The interpretation of these isotope ratios in rivers is therefore complex, but will help improve current understanding of the origin of Ca and Mg and their path taken from rock to river.…”

“…Gaillardet et al, 1999) as well as fractionation during weathering. Recent work has confirmed that the isotope ratios of Ca and Mg can be fractionated in the weathering environment Schmitt et al, 2003;Wiegand et al, 2005;Tipper et al, 2006a,b). In the headwaters of the Marsyandi river, Ca and Mg isotope ratios were interpreted to be controlled by fractionation from bedrock isotope ratios (Tipper et al, 2006a) based on small seasonal variations, and a discrepancy between bedrock and solute isotopic compositions.…”

“…Such data can be obtained by either multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) or thermal ionisation mass spectrometry and has already been demonstrated as a powerful new tool for investigating the global cycles of Ca and Mg (e.g. De La Rocha and DePaolo, 2000;Schmitt et al, 2003;Farkas et al, 2006;Tipper et al, 2006b) and the under-constrained weathering reactions by which these elements are released from the continental crust (e.g. Schmitt et al, 2003;Tipper et al, 2006a).…”

“…De La Rocha and DePaolo, 2000;Schmitt et al, 2003;Farkas et al, 2006;Tipper et al, 2006b) and the under-constrained weathering reactions by which these elements are released from the continental crust (e.g. Schmitt et al, 2003;Tipper et al, 2006a).…”

Constraining calcium isotope fractionation (δ44/40Ca) in modern and fossil scleractinian coral skeleton

“…Some studies argue for disequilibrium between outputs and inputs (Zhu and McDougall, 1998), whereas other studies suggest a balanced budget (e.g. Schmitt et al, 2003;Fantle & DePaolo 2005). Some modeling studies have proposed that variations of δ 44/40 Ca are influenced by secular variations in seawater composition, specifically by shifts affect the isotopic signals recorded in the skeleton, a careful screening for alteration using techniques such as microscopy, powder X-ray diffraction (XRD) and laser ablation ICP-MS is required prior to any analysis or data interpretation (Hathorne et al, 2011;Felis et al, 2012).…”