Keywords:Jurassic ridge-hydrothermal biosphere, Subduction of organic carbon , Sanbagawa eclogite
In order to know the fate of an organic carbon in deep subduction zone, we have observed the Sanbagawa eclogite (Tonaru eclogite) accompanying cupper-iron sulfides (so called Besshi mine type Cu-Fe sulfides). The sulfides are considered as precipitates related to the Jurassic ridge-hydrothermal alteration. In the eclogite, Cu-Fe sulfides contain silicate with graphite along cracks. The rims of the sulfides are replaces as Fe-Cu oxides. It is considered that the graphites were on the sulfide and along the interstitial domain such as cracks then rim of the oxides were overgrown. The graphite crystallization temperature calibrated using laser Raman peak shift, is estimated lower than 300 oC. It is obviously lower than that of the metamorphic temperature of the eclogite 550-600 oC. It clearly suggests that graphite was probably from the micro-bacteria with Cu-Fe sulfides in the hydrothermal zone in the Mid-oceanic ridge system. It is well known that the Cu-Fe oxides were formed in high P/T Sanbagawa metamorphism. Therefore overgrowth of the oxides on the studied sulfide-graphite association were in deep subduction zone. In summary, the Jurassic ridge-hydrothermal alteration provides bacteria cluster, and subsequently the organic carbon would be recycled down deep in the mantle via subduction zone.