TIMESCALE OF THE PROGRADE DECARBONATION IN A MAGMATIC-HYDROTHERMAL EVENT

Magmatic-hydrothermal systems carry metals, sulfur, and carbon from deep to shallow crust, supplying materials to the society and potentially affecting Earth’s long-term ecosystem of the Earth. Elements fluxes, and hence environmental consequences, are ultimately functions of the time-integrated amounts and durations. In this study, we estimate the duration of prograde metamorphism induced by fluid infiltration. The duration of prograde was 17.7 ~ 34.7 kyr, resulting in reasonably large fluxes of metal elements that corroborate the tonnages of ore deposits. This prograde process takes an order of magnitude longer to complete than the eruption of a felsic volcano (~1 kyr). If the prograde metamorphism approaches completion and transforms carbonate precursors to calc-silicate assemblages, the reactions release CO₂ at a rate of 0.21 ~ 0.71 Mt/y, similar to the CO₂ fluxes of volcanos that threaten ecosystem, such as Stromboli. The impact of magmatic-hydrothermal events on Earth’s environmental evolution awaits further quantitative studies.