Thermal and chemical evolution of the subarc mantle revealed by spinel-hosted melt inclusions in boninite from the Ogasawara (Bonin) Archipelago, Japan

A groundbreaking analysis of spinel-hosted melt inclusions in boninites from the Ogasawara Islands reveals two distinct geochemical groups, high-Si and low-Si, with ultra-depleted and less-depleted rare earth element patterns. These findings provide critical insights into the thermal and chemical evolution of the subarc mantle, showing that the onset of Pacific slab subduction at 52 million years ago triggered complex mantle dynamics. The study estimates primary boninite temperatures ranging from 1345 °C to 1421 °C under varying pressures, illustrating how slab fluid introduction led to distinct melting events in the mantle wedge. This research sheds light on the processes shaping arc magmatism and the role of mantle convection in subduction zones.

Umino, S., Kitamura, K., Kanayama, K., Tamura, A., Sakamoto, N., Ishizuka, O., & Arai, S. (2015). Thermal and chemical evolution of the subarc mantle revealed by spinel-hosted melt inclusions in boninite from the Ogasawara (Bonin) Archipelago, Japan. Geology, 43(2), 151–154. https://doi.org/10.1130/g36191.1