Subduction zones mineralogy

Helffrich G., Stein S., and Wood B. J. (1989) Subduction zone thermal structure and mineralogy and their relationship to seismic wave reflections and conversions at the slab/mantle interface. J. Geophys. Res. 94, 753-763. 

THERMAL STRUCTURE AND MINERALOGY OF THE SUBDUCTING PLATE. 2.1 Subduction Zone Thermal Models... 

As noted earlier, quantitative element fluxes in subduction zones are tricky. They depend on magma production rates, which are often poorly known. They also depend on specific fluid-fluxing or sediment melting models, which implicitly or explicitly invoke a specific thermal structure and mineralogy for the slab, a subject of much debate. 

Mineralogical and experimental evidence for very deep exhumation from subduction zones. J. Geodynam. 30, 61-76. 

A- -Vi = B- -V2 (where A, B are volatile free phases and Vi, V2 are hydrous phases or carbonates), involve hydrates and/or carbonates and change the mineralogy of a rock volume according to the stability fields of the minerals, but do not liberate a fluid. Prograde subduction zone metamorphism (as is true for any type of prograde metamorphism) generally reduces the amount of H2O that can be stored in hydrous minerals with depth. Thus, almost any part of the oceanic crust sooner or later becomes fluid saturated. In an equilibrium situation, the volatile content bound in hydrous phases and carbonates remains constant until fluid saturation occurs. Either continuous or discontinuous reactions may lead to fluid saturation in a rock. The point at which this occurs depends on initial water content, and pressure and temperature, and somewhat counter-intuitively, initial low water contents do not cause early complete dehydration, but delay the onset of fluid production to high pressures. 

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