Calcium Isotope Constraints on Recycled Carbonates in Subduction‐Related Magmas

Magnesium and Calcium Isotopic Geochemistry of Silica‐Undersaturated Alkaline Basalts: Applications for Tracing Recycled Carbon

“…Prior studies have shown that carbonatite‐metasomatized mantle xenoliths have large δ 44/40 Ca variations of 0.25‰–0.96‰, ranging from BSE‐like to low δ 44/40 Ca values (Figure 7; Ionov et al., 2019; Kang et al., 2017). This range overlaps the compositions of our studied WQO alkaline basalts (0.70‰ ± 0.05‰) and published carbonatites (0.44‰–1.05‰: Banerjee et al., 2021; Sun et al., 2021; Simon, 2022; 0.26‰ ± 0.25‰: Amsellem et al., 2020). Hence, carbonatite‐metasomatism also results in locally heterogeneous Ca isotopic compositions in the mantle, and the variations of mantle Ca isotopic composition depended on the Ca isotopic compositions of subducted carbonates.…”

“…Marine carbonates have a broad range of Ca isotopic compositions (in excess of 3‰; Fantle & Tipper, 2014), and the average δ 44/40 Ca values of Precambrian marine carbonate sediments are similar to those of BSE (Blättler & Higgins, 2017), while δ 44/40 Ca values of younger (<500 Ma) carbonates are lower than those of BSE values (Fantle & Tipper, 2014; Zhu et al., 2020). Recent studies also show that carbonatites through time have large δ 44/40 Ca variations, ranging from BSE‐like to low values (down to ∼0.07‰) (Amsellem et al., 2020; Banerjee et al., 2021; Simon, 2022; Sun et al., 2021). These results indicate that the Ca isotopic compositions of the WQO alkaline basalts may be attributed to the introduction of low δ 44/40 Ca subducted carbonates into their source.…”

“…Experimental studies have shown that the melting of subducted carbonate occurs mainly in the transition zone, producing carbonatite melts (Thomson et al., 2016) that either react with mantle peridotite to form carbonatite‐metasomatized peridotites or evolve further to form carbonated silicate melts and alkaline basalts at shallow depths (Dasgupta et al., 2013; Dasgupta & Hirschmann, 2010; Mallik & Dasgupta, 2013, 2014). Therefore, carbonatite, carbonated silicate and alkaline basalt magmas can provide important information on C recycling (Amsellem et al., 2020; Banerjee et al., 2021; Simon, 2022).…”

Samples Collected From the Floor of Jezero Crater With the Mars 2020 Perseverance Rover

“…Future insights from isotopic measurements of these martian rocks can be gained from the variations of stable isotopes of certain metals and halogens (e.g., Li, Cl, Mg, Ca, Fe, and Zn; see Johnson et al., 2004; Teng et al., 2017). These isotopic systems are sensitive to processes such as fractional crystallization, volatile degassing, and hydrothermal alteration and recorded by mass‐dependent isotope fraction in igneous rocks (e.g., Bellucci et al., 2017; John et al., 2012; Kang et al., 2017; Paniello et al., 2012; Simon, 2022; Teng et al., 2011; Tomascak, 2004; Watkins et al., 2009). Recent work measuring Ca isotopes, an element that has both multiple stable and radiogenic isotopes, exemplifies the emerging applications of non‐traditional stable isotope studies, as Ca isotopes can be used to test interpretations related to both thermal and chemical equilibrium by recording the degree of thermal and/or chemical metamorphism potentially modifying the original composition of the igneous rocks (Antonelli & Simon, 2020).…”