Melt-lamellae and low-viscosity channel in the uppermost lower mantle beneath Hawaii

邓凯 教授

成都理工大学

2026.04.17（星期五）15:00，理科二号楼2821

摘要：

        Water recycling between the Earth’s surface and deep interior is fundamental to habitability, mantle dynamics, sea-level change, and geochemical evolution. While significant work addresses the pathways of water transport and their consequences for mantle melting during mantle downwelling, key aspects in return of deep water remain elusive. Here we show that converted seismic waves from the 660-km discontinuity unravel a tilted lamellae of low melt fraction less than one percent, manifested as a strong, localized P-wave anisotropic layer, in the uppermost lower mantle beneath the Central Pacific. Water storage in the melt-lamellae and mass balance calculation indicates the water content in the Hawaiian plume-fed transition zone is probably less than ~0.1 wt. % above the 660. We suggest that, as mantle upwelling entrains recycled crust from the lowermost mantle, hydrous aluminous post-stishovite-to-stishovite transition triggers dehydration melting below the 660, where deformed plumes facilitate melt segregation, forming a low-viscosity channel key to triggering and generation of rapid, large-scale magmatism.

报告人简介：

邓凯，成都理工大学教授、博士生导师。2010年北京大学地球物理系本科毕业，2015年北京大学固体地球物理专业博士毕业，2015年9月至2016年12月在加拿大麦吉尔大学地球与行星科学系从事博士后研究，2017年4月入职成都理工大学，其间2019年7月至2020年7月赴英国伦敦大学访问。主要从事地球深部结构与地震活动性研究。