Blue diamonds: Valuable tracers of deep mantle fluids

Dr. Margo Regier

Thursday, June 10, 2021 - 11:00
Thematic Seminar
Dr. Margo Regier, Earth and Planets Laboratory

Water is an essential ingredient for the production of Earth’s deeply derived melts. However, the mechanisms by which the deep mantle becomes hydrous, and the mineral phases that can retain water during deep-slab subduction have remained contentious. In this talk, Dr. Regier will explore how the study of diamonds—in particular, boron-bearing blue diamonds—can assist us in understanding the deep-water cycle. Regier will overview the evidence for the sublithospheric origin of the dislocation networks and mineral inclusions found within blue diamonds, and will discuss what boron and carbon isotopes can tell us about their formation. Regier will suggest that the surprisingly heavy boron isotopic values found in sublithospheric blue diamonds are derived from seawater-altered, serpentinized oceanic slabs. These values are similar to those recently reported for deeply derived intra-plate magmas, suggesting that serpentinized oceanic lithosphere is not only an important volatile source for diamond formation in the deep mantle, but also an important source component in deeply derived intra-plate magmas.