Partition coefficient ( D ) distribution in pressure-temperature (PT) space. Logarithm of the partition coefficients (logD) between mantle and aqueous fluid within the investigated PT space. (a) Th, (b) U, (c) Pb, and (d) Yb. The temperature and pressure ranges and the color contour scale are the same for (a) to (d). The solid lines indicate along-slab (slab-mantle wedge interface) geotherms for two different thermal models. The squares indicate PT conditions at the point at which the hydrated mantle dehydrates (corresponding to <3> in Figure 1). The black line and square are from our model calculation, and the purple line and square are based on Syracuse et al. (2010).