Carbon sequestration under the forearc by COH-fluid mediated carbonation of serpentinites and peridotites

The carbon content in the atmosphere has a strong influence on climate and has changed dramatically over geological times. Consideration of the global carbon cycle has focused primarily on exchange between atmosphere, oceans and shallow crust because this likely mediates climate on millennial time scales. By contrast, carbon related processes in the deeper Earth remain less well understood, although a significant amount of Earth’s carbon budget (>90%) is present within deeper reservoirs.


In the Earth’s deep carbon cycle, carbon is transported from shallow crustal reservoirs into the Earth’s mantle via subduction and returned to the atmosphere and hydrosphere during volcanism. A significant amount of carbon is subducted every year (40 - 66 MtC/a) from which a poorly constrained fraction is released into fluids and melts in the subduction zone from where some is then returned to shallower reservoirs (crust, biosphere, atmosphere). However, some carbon is subducted deeper into the mantle.


The fate of carbon bearing fluids released during subduction is the focus of this research project combining high pressure experiments with field observations. If carbon bearing fluids migrate into, and react with surrounding lithologies such as serpentinites and peridotites, carbon from the fluid might be sequestered into newly formed carbonates. In this talk we will provide insights into the efficiency, timescale, magnitude and mechanisms of this fluid/rock interaction. Our results are fundamental for constraining carbon fluxes and reservoirs in the forearc and subarc regions of the mantle wedge.