Phengite identified as key carrier of halogens into Earth's deep mantle

Surface volatiles – chemicals that readily change to gases or fluids at relatively low temperatures and pressures – are transported to Earth through subduction zones, with some transported into the deep mantle and others to shallower depths. According to conventional models, halogens such as fluorine (F) and chlorine (Cl) are largely released at shallow depths when hydrated minerals decompose, making it difficult to access the deep mantle. However, a new study has identified high-density salt inclusions in deep-sea diamonds and fluorine enrichment of mantle minerals, indicating that some halogens survive transport to great depths.