Volatile fluxes from volcanoes

Abstract

Abstract Volatile fluxes from Mid Ocean Ridge (MOR) and subaerial volcanism have been estimated or re‐evaluated using several natural tracers‐ 3 He, 210 Po, SO 2 ‐and chemical ratios of volatile species in lavas and volcanic gases. These estimates confirm the net predominance of anthropogenic fluxes over volcanic fluxes for CO 2 , SO 2 and trace metals. They also suggest that, while most of the volatiles transferred during MOR volcanism come from the mantle, volatiles stored at the surface of the Earth supply an appreciable fraction of subaerial fluxes and can be the dominant source for some of them. The surface inventory of volatile species cannot result from steady‐state degassing with constant rate and needs much greater fluxes in the past or other volatile supply processes. This inventory is the result of several of the following processes: capture of the solar nebula and its subsequent partial escape, impact degassing of accreting bodies, and, from Archean to present mantle, degasssing through volcanism and associated phenomena, with recycling into the mantle through subduction.