Figure 2
The εHfinitial vs absolute age plot of the black shale samples, compared to zircon47,48 and komatiite49,50,51 data. It shows komatiites as potential source for the older Duffer Formation. Younger Pilbara black shales show lower initial Hf. Black shales older than 3–3.2 Ga show the predominant process of formation of juvenile crust, whereas younger samples indicate crustal reworking as the dominant process. From this data set, the change in the processes can be dated to be not older than 3.2 Ga.
