UMD: Carnegie’s Shimizu on mantle carbon

2018 University of Maryland Geology Colloquium Series

Friday, September 14th 2018 at 3:00 pm
in PLS 1130 (UMD- College Park)

Kei Shimizu
Carnegie DTM

Carbon contents in Earth’s mantle domains constrained using silicate melt inclusions and geochemical modeling

Estimates of carbon contents in mantle sources of mid-ocean ridge basalts (MORBs) and ocean island basalts (OIBs) can provide constraints on the origin of the geochemically heterogeneous mantle. Furthermore, carbon fluxes from MORB and OIB mantle sources to the atmosphere provide constraints for understanding Earth’s climate stability and habitability. However, carbon contents in these mantle sources are difficult to estimate since most MORBs and OIBs have lost significant portions of their CO2 through degassing. Silicate melt inclusions, which are small amount of quenched magma trapped in crystals, preserve the CO2 contents in MORB and OIB magmas at depths of melt inclusion entrapment prior to significant CO2 degassing. In this talk, I will discuss carbon contents for MORB mantle sources (Siqueiros and Garrett transform fault in the East Pacific Rise) and an OIB mantle source (Borgarhraun in northern Iceland) estimated u! sing data from silicate melt inclusions in combination with geochemical modeling of mantle melting, magma degassing and mixing. The preliminary results suggest that the Iceland mantle source (~400 ppm CO2) may be significantly more carbon-rich compared to an EPR-type MORB mantle source (~100 ppm CO2).

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