Premium
Phase Transition of Enstatite‐Ferrosilite Solid Solutions at High Pressure and High Temperature: Constraints on Metastable Orthopyroxene in Cold Subduction
Author(s) -
Xu Jingui,
Fan Dawei,
Zhang Dongzhou,
Guo Xinzhuan,
Zhou Wenge,
Dera Przemyslaw K.
Publication year - 2020
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2020gl087363
Subject(s) - enstatite , subduction , geology , phase transition , slab , oceanic crust , metastability , phase (matter) , mineralogy , analytical chemistry (journal) , chemistry , tectonics , thermodynamics , seismology , geophysics , physics , meteorite , organic chemistry , chromatography , astronomy , chondrite
(Mg, Fe)SiO 3 orthopyroxene is an abundant mineral of oceanic subducting slabs. In‐situ high‐pressure and high‐temperature single‐crystal X‐ray diffraction has been used to investigate the phase transition of orthopyroxene across the enstatite‐ferrosilite (En‐Fs) join (En 70 Fs 30 , En 55 Fs 45 , En 44 Fs 56 and Fs 100 ) up to 24.3 GPa and 800 K, simulating conditions within the coldest part of a subduction zone consisting of an old and rapidly subducting slab. Instead of the orthopyroxene → high‐pressure clinopyroxene transition, the α‐opx → β‐opx and β‐opx → γ‐opx phase transition are observed at 7.2–15.3 and 11.6–21.1 GPa (depending on the Fs content), respectively. This study indicates that the pressure‐induced phase transition of (Mg, Fe)SiO 3 orthopyroxene under relatively low temperature (<800 K) could be different than those occurring under relatively high temperature (>800 K). Additionally, the α‐opx → β‐opx → γ‐opx phase transition could exist within the center of the extremely cold slabs (like Tonga), where such low temperature persists to ~600‐km depth.