Episodic zircon ages, Hf isotopic composition, and the preservation rate of continental crust

U/Pb detrital zircon ages from global modern river sediments define eight peak clusters centered at 2700, 2500, 2010, 1840, 1600, 1150, 600, and 300 Ma. These clusters extend vertically into both positive and negative εHf(T) space and are similar to those in orogenic granitoids that correlate well with supercontinent formation. We suggest that the clusters are preservation peaks that reflect juvenile and reworked continental crust selectively preserved during continental collisions. The greatest contribution of juvenile continental crust is associated with the 1600 and 1150 Ma clusters and may reflect a change in the style of collisional orogens in the Paleoproterozoic involving thicker and stronger lithosphere. Age gaps at 2400-2200, 1400-1300, 900-650, and 185-120 Ma represent times when crustal production and recycling rates were about the same. Although some new continental growth may occur during continental collisions, supercontinent assembly does not require an increase in production rate of continental crust. Rather, we suggest that the preservation rate increases by an increased probability of capture of both new and reworked continental crust in collisional orogens.7 page(s