| 研究実績の概要 |
Carbon dioxide-bearing saline fluid inclusions are also reported from sub-arc mantle peridotite xenoliths: 3.7 wt% NaCl in Ichinomegata lherzolites, Northeast Japan arc [Kumagai et al., 2014] and 5.1 wt% NaCl in Pinatubo harzburgites, Luzon arc [Kawamoto et al., 2013]. These findings indicate that aqueous fluids in the subduction channel and mantle wedge can contain certain amounts of C and Cl.
Synchrotron radiation X-ray fluorescence (XRF) analysis is conducted to know Rb, Sr, and Pb partitioning between aqueous fluids and melts simultaneously at high-temperature and high-pressure conditions [Kawamoto et al., 2014]. There is a positive correlation between partition coefficients and pressure, as well as salinity. The fluid component is characterized by enrichment of alkali, alkali earth elements, and Pb. Such features can be explained if the fluid component is a saline fluid, because alkali earth elements and Pb are much less mobile with Cl-free fluids than Cl-rich fluids. We suggest that slab-derived supercritical fluids contain Cl, and separated aqueous fluids inherit much of the Cl and some of the large-ion lithophile elements [Kawamoto et al., 2012, 2014]. .
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