2011/05/02 by Kenji Mibe, Tatsuhiko Kawamoto, Kyoko N. Matsukage +2 · 2 citations
Earth and Planetary Sciences · #Geological and Geochemical Analysis #High-pressure geophysics and materials #earthquake and tectonic studies #Geology #Slab #Subduction #Adakite #Magmatism #Partial melting #Crust #Oceanic crust #Petrology #Volcanic arc #Basalt #Geochemistry #Geophysics #Seismology #Tectonics
paper · doi:10.1073/pnas.1010968108
openalex publication_date 2011/05/02 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
The second critical endpoint in the basalt-H(2)O system was directly determined by a high-pressure and high-temperature X-ray radiography technique. We found that the second critical endpoint occurs at around 3.4 GPa and 770 °C (corresponding to a depth of approximately 100 km in a subducting slab), which is much shallower than the previously estimated conditions. Our results indicate that the melting temperature of the subducting oceanic crust can no longer be defined beyond this critical condition and that the fluid released from subducting oceanic crust at depths greater than 100 km under volcanic arcs is supercritical fluid rather than aqueous fluid and/or hydrous melts. The position of the second critical endpoint explains why there is a limitation to the slab depth at which adakitic magmas are produced, as well as the origin of across-arc geochemical variations of trace elements in volcanic rocks in subduction zones.