New insights into carbon fluid chemistry and graphite precipitation: SIMS analysis of granulite facies graphite from Ponmudi, South India

Slow graphite carbon self-diffusion rates and a strong dependence of 13C/12C fractionations on fluid chemistry can be combined with secondary ion mass spectrometry (SIMS) analyses of 13C/12C of graphite to fingerprint graphite precipitation mechanisms and carbon chemistry of crustal fluids. The δ13C variations in single graphite grains in granulite facies rocks from Ponmudi, South India approach 10‰ and are interpreted to reflect three distinct generations of graphite formation and fluid infiltration, illustrating the potential of SIMS microdomain graphite analyses for deciphering crustal fluid influx histories. Our analyses provide insight into a longstanding debate in crustal metamorphism of South India, indicating that the fluid–rock interaction history included early, middle, and late interactions with C–O–H fluids.