FIGURE 1. A 2.5-Gyr-old banded iron formation from Hamersley, Australia.
From the following article:
Subducted banded iron formations as a source of ultralow-velocity zones at the core–mantle boundary
David P. Dobson and John P. Brodholt
Nature 434, 371-374(17 March 2005)
doi:10.1038/nature03430
The grey bands predominantly contain the iron oxide haematite and the brown bands are rich in siliceous chert.
