Figure 5

Model for the genesis of three types of diamonds. (A) Oceanic and super-deep continental diamonds (cores only) form in the mantle transition zone using subducted organic carbon, and are then brought to the lithospheric levels by mantle plumes. Continental diamonds grow or overgrow (as rims over the super-deep diamonds) in the continental lithosphere. (B) Oceanic diamond-bearing rocks are accreted onto continental margins as fragments of obducted oceanic plateaus or ocean islands.