Apatite CO2 and H2O as Indicators of Differentiation and Degassing in Alkaline Magmas

Abstract Apatite can incorporate significant amounts of H2O and CO2, potentially recording volatile abundance behavior during magma evolution. Here we conducted in situ measurements CO2 concentrations apatite, along with elemental compositions, from two contemporaneous alkaline volcanic suites (Tianbao Tudiling) the South Qinling belt central China to better understand contents evolving melts. alkali basalts Tianbao contains variable ranging <100 ppm 2.7 wt.% 0.1 0.6 wt.%. REE-enriched trachytes, which evolved basalt, shows significantly lower a continuous decrease fractionation. The observations suggest that loss commenced at early stages evolution, whereas occurred subsequent fractionation tandem REE-enrichment. In comparison, apatite grains Tudiling trachyte, is genetically linked carbonatite, contain higher (0.6 1.5 wt.%) but REE than trachytes. trachyte inferred have crystallized carbonated prior separation carbonatitic melts, where liquid immiscibility led enrichment into characteristics provide valuable insights different evolutionary processes alkaline/carbonatitic magmas, H2O, systems.