Continental crust sediment recycling

Figure 10.1 is a generalized model of the rock cycle. Both the sediments and the continental crust are recycled the former by processes of weathering, erosion, transportation, deposition, burial, uplift, and re-erosion and the latter by resetting... 

One of the more robust measures of plume versus arc contributions to the continental crust is the La/Nb ratio, for intraplate magmas typically have La/Nb < 1.0, whereas arc magmas have La/Nb > 1.0. This ratio was used by Rudnick (1995) to estimate that between 10 and 35% of the continents formed from an intraplate component. More recently, using revised crustal Nb concentrations, Barth et al. (2000) calculated that between 5 and 20% of the continental crust is of intraplate origin. However, Plank (2005) urges some caution in the acceptance of these proportions, for the impact of sediment recycling could overinflate the arc contribution to crustal growth. 

Figure 10.1. A generalized diagram for the steady-state rock cycle. Sediments, S, and continental crystalline crust, C, masses are in units of metric tons. Ss, Cs, Sc, Cc, and M are fluxes in units of 109 tons y-l due to erosion of sediments, metamorphism, erosion of crystalline rocks, recycling of crystalline rocks (resetting of ages during tectogenesis), and cycling of oceanic crust, respectively. Total sedimentation rate is 9 x 109 tons y-l. (After Gregor, 1988.)...

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