1. Carbon Cycling in Subduction Zones implications for mantle-exosphere exchange
Rajdeep Dasgupta

2. Modern-day fluxes and reservoirs of carbon

3. Modern-day fluxes and reservoirs of carbon

4. sediment
crust
mantle

5. sediment basalt peridotite
(Sciutto and Ottonello, 1995; Kerrick & Connolly, 2001; Sleep and Zahnle, 2001; Jarrard, 2003; Alt, 2004)

6. Carbonated basalts
(Yaxley and Green, 1994; Yaxley and Brey, 2004; Dasgupta et al., 2004, 2005)

7. Carbonated sediments
(Thomsen and Schmidt, 2008; Tsuno and Dasgupta, submitted)

8. Carbonated peridotite
(Wallace and Green, 1988; Falloon and Green, 1989; Dasgupta and Hirschmann, 2006)

9. How do we get carbon out of the slab in modern subduction zones?
● Fluid infiltration induced decarbonation of basalts and sediments
(Molina and Poli, 2000; Connolley, 2005; Gormann et al., 2006; Poli et al., 2009)
(Gormann et al., 2006)

10. How do we get carbon out of the slab in modern subduction zones?
● Mantle wedge plume/ intrusions and sediment detachment ?
(Currie et al., 2007)
(Gerya and Yuen, 2003)

11. Deep subduction of carbon in ancient past ?DT
Radiogenic heat production
(Sizova et al., 2010)
Modern-style subduction may have initiated at Ga, with T hotter than the present mantle by as much as ~ oC

14. Subduction zone cycling of carbon through time
Modern Earth observes efficient ingassing of exosphere carbon and there is likely a net influx of surficial carbon into the deep mantle
More than 3 b.y. of the Earth’s history likely have seen inefficient ingassing of carbon to the interior
The residence of carbon in the mantle must have increased through time

15. Questions related to subduction zone carbon cycling
How variable is the behavior of carbonated sediments in subduction zones through space and time?
What is the influence of slab released carbon on mantle wedge melting? How does it alter the role of water and halogens on wedge melting?
What is the nature of metasomatic interaction between slab released (carbonated) melt and mantle wedge peridotite?
What is the carbon content of primary arc magmas? – how do we determine that?
What is the back-arc carbon flux? How does it differ from that of arc and MOR?
What is the behavior of reduced carbon?