New Research Opportunities in the Earth Sciences - New Research Opportunities in the Earth Sciences - page 25

project is completed over the next decade, planning efforts will need to be undertaken
throughout the decade to achieve the capabilities needed for resolving key deep Earth
system controversies.
Quantification of Mantle Volatile Fluxes
The stored quantity and flux of water into and out of the mantle are critical
factors for sustaining life, facilitating plate tectonics (by making faults weak and
lowering the viscosity of the mantle), and creating volcanism. As the universal
solvent, the flux of water is intimately connected to most geochemical and volatile
cycles and hence to the weathering of continents and the formation of mineral and ore
deposits. A basic understanding of the dynamic Earth cannot be achieved without
quantitative knowledge of the distribution and behavior of water and the feedback
between the water cycle in the solid Earth and the climate system. Yet the sign of the
net flux of water between Earth's interior and the near-surface hydrosphere is not
even known (e.g., Hirth and Kohlstedt, 1996; Bercovici and Karato, 2003; Ohtani et
al., 2004; Hirschmann, 2006; Olson, 2010).
Figure 2.7 Cycling of volatile molecules through Earth's mantle is known to have an
important role in regulating the level of carbon dioxide in the atmosphere.
Mineralogists have discovered that many high-pressure minerals, such as the
wadsleyite form of olivine present in the transition zone, can contain large amounts of
water as hydrogen dissolved into their crystal structures. Current research points to a
large fraction of our planet's volatile budget being locked up inside the solid Earth
(Kellogg et al., 2004). SOURCE: Figure provided by R. Dasgupta and M.
Hirschmann.