Studies on budget of organic matter in mantle and crust of arc during subduction and magmatism

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The purpose and targets of the project are the understanding of the behavior and budget of volatile components an the crust and wedge mantle during subduction, accretion and magmatism in arc systems based on EPMA, CNS, FT-JR, Py-GC, Py-GC/MS and stable carbon isotopes analyses for natural rocks, and experiments using natural glass + H_2O + hydrocarbon under high P-T conditions.The results of researches are summarized as follows ;1)Carbonaceous matter in S-type granitoids was derived from interaction between granitoid magmas and surrounding pelitic rocks. Particulate carbonaceous materials in minerals in the granodiorite contain long-aliphatic hydrocarbon bonds, oxygen-bearing organic compounds, and aromatic fragments. The distribution of these organic groups differs between feldspar, quartz and biotite. We conclud that (a) most organic matter is released from the system during partial melting of pelitic rocks, however, (b) a small amount is trapped in highly viscous felsic melt and pol … More ymerized during cooling and crystallization of granitoid magma under differing oxidation conditions.2) Carbonaceous matter including B, N and Cl was found in olivine and pyroxene from the Horoman Peridotite Mass and high-Mg andesite. Aromatic compounds with Cl and N, n-C_8 alkane and n-C_<8-12> alkane were detected from pyrolyzed bulk rocks of spinel and plagioclase lherzolite, and harzburgite in the Horoman Peridotite Mass. Aromatic compounds such as toluene and naphthalene were found from pyrolyzed bulk rocks of high-Mg andesite. δ ^<13>C values of non-carbonate carbon are lherzolite : -25.5‰ vs PDB, harzburgite : -23.4‰, and dunite : -21.9‰ and -28.0‰. These results indicate that the Horoman Peridotite Mass and HMA magma were influenced by fluid, which was probably derived from subducted slab, in wedge mantle.3)Preliminary experiments were carried out to examine transformation of sediment -derived hydrocarbons in felsic magma and during its solidification at middle crustal condition. Starting materials and conditions were : granitic glass + hydrocarbon [n-hexane and n-tetracosane] + H_2O ; 5kb, 900℃. Results showed that remnant carbonaceous materials remained in all experimental products, not only as carbonate and graphite but also as solid state hydrocarbon, indicating that polymerization occurred. Less