Wehrlites from continental mantle monitor the passage and degassing of carbonated melts
Sonja Aulbach, A‐Bing Lin, Yaakov Weiss, Gregory M. Yaxley
Abstract
Continental rifting has been linked to the thinning and destruction of cratonic lithosphere and to the release of enough CO 2 to impact the global climate. This fundamental plate tectonic process facilitates the infiltration and mobilisation of smallvolume carbonated melts, which may interact with mantle peridotite to form wehrlite through the reaction: enstatite dolomite (melt) = forsterite diopside CO 2 (vapour). Application to mantle xenolith suites from various rifts and basins shows that 2.9 to 10.2 kg CO 2 are released per 100 kg of wehrlite formed. For the Eastern Rift (Africa), this results in estimated CO 2 fluxes of 6.5 4.1 Mt yr -1 , similar to estimates of mantle contributions based on surficial CO 2 surveys. Thus, wehrlite-bearing xenolith suites can be used to monitor present and past CO 2 mobility through the continental lithosphere, ultimately with diffuse degassing to the atmosphere. They may also reveal the CO 2 flux in lithospheric provinces where carbonated melts or continent-scale rifts are not observed at the surface.