R8: Metamorphic rocks and tectonics

[R8-10] Stable isotope geochemistry of the olivine-bearing dolomitic marble in the Hida Belt, Japan

[Presentation award entry]

*Hironobu Harada¹, Tatsuki Tsujimori¹, Hideko Takayanagi¹, Yasufumi Iryu¹ (1. Tohoku Univ.)

Keywords:Hida Belt, dolomitic marble, carbon isotope, oxygen isotope, abiotic methane synthesis

Marble, a metacarbonate rock, occurs in various orogenic belts throughout the Earth's history. We newly determined C–O isotopecompositions of upper amphibolite-facies dolomitic marbles from the Hida Belt, Japan. The C–O isotope compositions of dolomitic marble are characterized by δ¹³C[VPDB] = –3.3 to +2.8‰, δ¹⁸O[SMOW] = +8.6 to +20.0‰ respectively; overall, calcite tends to show lower δ¹³C values than dolomite. New data can be explained by the result of the olivine forming decarbonation reaction.