Controls on riverine calcium isotope ratios during basalt weathering in the Skagafjörður watershed, Iceland

Behaviour of Sr, Ca, and Mg isotopes under variable hydrological conditions in high-relief large river systems

“…Previous studies have suggested that secondary carbonate precipitation, clay adsorption, and cation exchange preferentially take up lighter Ca and Mg isotopes (Brazier et al, 2019;Cenki-Tok et al, 2009;Jacobson and Holmden, 2008;Nelson et al, 2021;Teng, 2017;Tipper et al, 2006a). In contrast, plant growth preferentially takes up heavy Mg as well as light Ca isotopes (Black et al, 2008;Bolou-Bi et al, 2010;Bolou-Bi et al, 2012;Nelson et al, 2022;Page et al, 2008;Schmitt et al, 2003;Wiegand, 2005), resulting in liquid phases having light Mg and heavy Ca isotopic compositions, which is inconsistent with the patterns observed for δ 44/40 Ca and δ 26 Mg values in Jinsha River waters (Fig. 8b).…”

“…3a) (Clow and Mast, 2010;Georg et al, 2006;Torres et al, 2015). Since Ca is the dominant element in carbonates but a trace element in clay minerals, we expect the weathering of secondary silicates to have little effect on the riverine δ 44/40 Ca values (Nelson et al, 2022).…”

“…rocks, waters, plants), represent important nutrients in the ecosystem (Griffith et al, 2020;Tipper, 2022), and their elemental cycles are directly coupled to the carbon cycle through silicate weathering and carbonate precipitation (Berner and Berner, 2012;Wimpenny et al, 2011). Stable Ca and Mg isotopes can be fractionated during the secondary processes described above and can therefore be used to trace these processes within weathering environments (Cenki-Tok et al, 2009;Ewing et al, 2008;Fan et al, 2016;Fantle and Tipper, 2014;Fries et al, 2019;Holmden and Bélanger, 2010;Ma et al, 2015;Nelson et al, 2021;Nelson et al, 2022;Opfergelt et al, 2014;Ryu et al, 2016;Saulnier et al, 2012;Tipper et al, 2006a;Tipper et al, 2012a;Wimpenny et al, 2014;Wimpenny et al, 2010). Although rock endmembers have a wide range of Ca and Mg isotopic compositions, which represents a challenge for distinguishing the controls (solute sources vs. secondary fractionation) on riverine Ca and Mg isotopes (Fantle and Tipper, 2014;Pogge von Strandmann et al, 2019b;Tipper et al, 2006a;Tipper et al, 2008), radiogenic strontium (Sr) isotopes can provide complementary evidence to deconvolve fractionation and lithological controls (Tipper et al, 2006c).…”

A review of measurement for quantification of carbon dioxide removal by enhanced weathering in soil

“…Novel isotope tracers, such as magnesium (Mg), lithium (Li), silicon (Si), stable strontium (Sr) and calcium (Ca) can be used to trace many additional processes, including secondary mineral formation and plant uptake (Pistiner and Henderson, 2003;Georg et al, 2007;Opfergelt and Delmelle, 2012;Andrews et al, 2016;Pogge von Strandmann et al, 2021;Nelson et al, 2022). The majority of work to date on these isotope systems has revolved around quantifying fractionation factors and natural element cycling (Penniston-Dorland et al, 2017;Teng et al, 2017), but EW-specific applications are increasing (Pogge von Strandmann et al, 2021;Vienne et al, 2023).…”

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“…Novel isotope tracers, such as magnesium (Mg), lithium (Li), silicon (Si), stable strontium (Sr) and calcium (Ca) can be used to trace many additional processes, including secondary mineral formation and plant uptake (Pistiner and Henderson, 2003;Georg et al, 2007;Opfergelt and Delmelle, 2012;Andrews et al, 2016;Pogge von Strandmann et al, 2021;Nelson et al, 2022). The majority of work to date on these isotope systems has revolved around quantifying fractionation factors and natural element cycling (Penniston-Dorland et al, 2017;Teng et al, 2017), but EW-specific applications are increasing (Pogge von Strandmann et al, 2021;Vienne et al, 2023).…”