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

Surface volatiles—chemical substances that easily become gases or fluids at relatively low temperatures and pressures—are transported into Earth through subduction zones, with some being 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 hydrous minerals break down, making it difficult for them to reach the deep mantle. However, a new study has identified high-density saline inclusions in deep diamonds and fluorine enrichment in mantle minerals, indicating that some halogens survive transport to great depths.