Figure 1.
(A) Histogram of more than 100,000 detrital zircon analyses showing several peaks in their U-Pb crystallization ages over the course of Earth’s history (Voice et al., 2011), which are very similar to the ages of supercontinents. Also shown is the apparent thermal gradient versus age of peak metamorphism for the three main types of granulite-facies metamorphic belts (Brown, 2007, 2014). UHT—ultrahigh temperature; HP—high pressure; UHP—ultrahigh pressure. (B) Histogram of the ages of ancient and modern passive margins (Bradley, 2008) and normalized seawater 87Sr/86Sr curve (Shields, 2007). (C) Running mean of initial Hf in ~7000 detrital zircons from recent sediments (Cawood et al., 2013) and moving average distilled from compilation of ~3300 18O analyses of zircon versus U-Pb age (Spencer et al., 2014).