Melt-rich lithosphere-asthenosphere boundary inferred from petit-spot volcanoes

Junji Yamamoto, Jun Korenaga, Naoto Hirano, Hiroyuki Kagi

Research output: Contribution to journalArticlepeer-review

38 Citations (Scopus)


Young basaltic knolls have been discovered on the old oceanic lithosphere, namely petit-spot volcanoes. Based on their geochemical signatures, they have presumably originated from partial melts in the asthenosphere. However, there is no direct information on the depth provenance of petit-spot formation. Here we report new geothermobarometric data of rare mantle xenoliths discovered from petit-spot lavas exhibiting a geotherm much hotter than expected for the ca. 140 Ma seafloor on which petit-spots were formed. Such an anomalously hot geotherm indicates that melt porosity around the lithosphere-asthenosphere boundary (LAB) must be as high as a few percent. Such high melt porosity would be possible by continuous melt replenishment. Excess pressure induced by the outer-rise topography enables horizontal melt migration along the LAB and sustains a continuous melt supply to petit-spot magmatism. Given the general age-depth relationship of ocean basins, a melt-rich boundary region could also be a global feature.

Original languageEnglish
Pages (from-to)967-970
Number of pages4
Issue number11
Publication statusPublished - 2014
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Geology


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