Interpretive model for the formation of microdiamonds and associated ultrahigh-pressure minerals in the oceanic mantle and for their incorporation into ophiolite-hosted chromites within the mantle transition zone (TZ). FAB—forearc basalts; IAT—island arc tholeiite; LM—lower mantle; MORB—mid-oceanic ridge basalt; MOR—mid-ocean ridge; UM—upper mantle; P—pressure. See text for discussion. Data are from Liou et al. (2014) and Yang et al. (2014, 2015b).