R8: Metamorphic rocks and tectonics

[R8-05] The Physico-chemical evolution of carbonaceous material during low-grade metamorphism of Archean stromatolites by Raman spectroscopy and carbon isotopes

*Kiran Sasidharan¹, Madhusoodhan Satish-Kumar¹, Yoshihiro Nakamura², Tomozaku Hokada³, Hiroaki Ohfuji⁴ (1. Niigata Uni., 2. Geological Survey of Japan, AIST, 3. National Institute of Polar Research, 4. Tohoku Uni.)

Keywords:Raman Spectra of carbonaceous material thermometry, Carbon isotope thermometry, Chitradurga Schist Belt, Hydrothermal infiltration, Degassing and dissolution reprecipitation

This study compares the carbonaceous material (CM) physicochemical conditions in carbonates during metamorphism, using Raman spectra of CM and carbon isotopic composition. Our results suggest that inconsistencies between the temperature of equilibration can be due to (1) post-metamorphic hydrothermal fluid infiltration inferred by a shift in δ¹⁸O without change in δ¹³C of carbonates (2) negative δ¹³C shift in CM is caused by dissolution recrystallization after CO₂ degassing lowered CM crystallinity.