The amount of non-anthropogenic versus anthropogenic input of CO2 to the Earth’s atmosphere is currently a hotly debated topic. The most direct way to estimate volatile flux from the interior of the Earth is by measuring the concentration of the volatiles in basaltic magma as it moves to the surface. While the CO2 of naturally quenched glasses from mid-ocean ridge basalts (MORBs) and ocean island basalts can be measured, estimates of mantle-derived CO2 content of magmas is much more difficult to estimate. Michael and Graham seek to increase the accuracy of mantle-derived carbon dioxide concentration and flux estimates by measuring CO2 and trace element data from ultra-depleted mid-ocean ridge basalts (UD-MORBs) which, with low initial CO2 content and deep eruption depths, preserve their CO2 inventory since formation in the mantle.
Michael and Graham confirm that the most reliable measurements of CO2 in ocean basalts are for UD-MORB. Presenting new CO2 and trace element data from UD-MORBs, together with other proxy elements for CO2 and previously published geochemical analyses, they then calculate revised values for CO2 flux from the mantle at 0.3% of the anthropogenic addition to Earth’s atmosphere.
Dredge depths for studied samples were obtained from SESAR (System for Earth Sample Registration) whenever possible. PetDBwas surveyed for MORB glasses. Locations of samples used in the study were plotted using GeoMapApp.
Fig 1.Locations of ultradepleted mid-ocean ridge basalts used in this study
Michael, P., and Graham, D. (2016) The Behavior and Concentration of CO2 in the Suboceanic Mantle: Inferences from Undegassed Ocean Ridge and Ocean Island Basalts. Lithos 236-237, doi:10.1016/j.lithos.2015.08.020