The Carbon Subduction Efficiency: a parameter, or a variable in space and time?

With subduction zones being the main loci of ingassing of carbon into Earth’s interior, it is critical to constrain the efficiency of deep carbon subduction versus carbon recycling back through volcanic arcs. What are the latest constraints on the fate of carbon during subduction of the oceanic lithosphere with crust and sediments? How much carbon gets subducted deeper past the arc processing zones, and how much gets released from the subducting slab? What is the expected flux of carbon out of the slab because of carbonate dissolution in fluids, and hydrous slab melting? What constraints exist based on experimental petrology, thermodynamic modeling of fluid–rock interactions? How much carbon is expected to come out of the slab and how does that compare with the estimated flux of CO2 out of present-day volcanic arcs? These questions will be addressed in my presentation.