2:15 PM - 2:30 PM
[SGC50-01] Geochemical connection between HIMU-FOZO-PREMA: two-stage dehydration of oceanic crust with layered structure
Keywords:HIMU, FOZO, PREMA, MORBs, OIBs
To elucidate the origin of mantle reservoirs, geochemical modeling has been conducted, in which origin of HIMU, FOZO and PREMA is discussed. The results suggest that MORBs with high frequency (common MORBs) without significant chemical modification during subduction have chemical composition that is suitable for producing PREMA. It suggests the importance of recycling of dry MORBs for the production of OIBs source. Dehydration of common MORBs in subduciton zones can produce FOZO isotopic signatures if amount of dehydrated water is close to the maximum amount (4 %) of dehydrated aqueous fluid in subduction zones. Thus, FOZO-PREMA isotopic array can be explained by recycling of common MORBs that release various amount of aqueous fluid during subduction. For the production of HIMU, additional dehydration (~2%) at high pressure is required. As high pressure dehydration release supercritical fluid with relatively high U/Pb and low Th/Pb ratios, chemical fractionation during dehydration is different from the sub-arc process. This difference can explain isotopic difference between HIMU and FOZO.