Phase compositions in carbonated oceanic crust

High-pressure experiments were performed at 3–15 GPa and 700–1300°C in a 1000-ton multi-anvil press at the SEDI-Lab, China University of Geosciences (Wuhan), to investigate the phase relations of subducted carbon-bearing oceanic crust. Thirty-four samples were recovered after the experiments. All minerals in the recovered experimental charges were analyzed with an electron probe micro-analyzer (EPMA, JXA-8230), installed at the State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences (Wuhan). The accelerating voltage was 15 kV, and counting times were 10 s for the measured elements and 5 s for each side of the background. A beam current of 20 nA and beam size of 1–2 µm were used for silicate minerals and Ti-rich oxides. For quench liquids, a beam current of 10 nA and beam size of ~5–20 µm.