Electromagnetic evidence for volatile-rich upwelling beneath the society hotspot, French Polynesia

Noriko Tada , Pascal Tarits (1, 2) , Kiyoshi Baba , Hisashi Utada , Takafumi Kasaya , Daisuke Suetsugu

1 LDO - Domaines Océaniques
2 IUEM - Institut Universitaire Européen de la Mer

We have conducted a seafloor magnetotelluric survey that images, for the first time, three-dimensional electrical conductivity structure in the upper mantle beneath the Society hotspot. A striking feature in our model is a high-conductivity anomaly a few hundred kilometers in diameter, which is continuous from the lowest part of the upper mantle to a depth of approximately 50 km below sea level. Using theoretical and experimental results from mineral physics, we interpret the high-conductivity anomaly as evidence of the melt fraction up to 2.2 vol.%, which is robust regardless of assumed temperature, and the existence of carbonated silicate melt beneath the hotspot. Our results suggest that the Society hotspot is a pathway for ascending volatiles from the deeper part of the upper mantle to the surface.

Keywords: hotspot; marine magnetotellurics; three-dimensional inversion; volatiles; partial melt

Domains: Sciences of the Universe [physics]; Earth Sciences

Noriko Tada, Pascal Tarits, Kiyoshi Baba, Hisashi Utada, Takafumi Kasaya, et al.. Electromagnetic evidence for volatile-rich upwelling beneath the society hotspot, French Polynesia. Geophysical Research Letters, 2016, 43, pp.12,021-12,026. ⟨10.1002/2016GL071331⟩. ⟨insu-03684934⟩