Work

Melt focusing along lithosphere–asthenosphere boundary below Axial volcano

Year: 2025

Type: article

Abstract: Beneath oceanic spreading centres, the lithosphere-asthenosphere boundary (LAB) acts as a permeability barrier that focuses the delivery of melt from deep within the mantle towards the spreading axis1. At intermediate- to fast-spreading ridge crests, the multichannel seismic reflection technique has imaged a nearly flat, 1-2 km wide axial magma lens (AML)2 that defines the uppermost section of the LAB3, but the nature of the LAB deeper into the crust has been more elusive with some clues gained from tomographic images, providing only a diffuse view of a wider halo of lower velocity material seated just beneath the AML4. Here we present three-dimensional (3-D) seismic reflection images of the LAB extending deep (5-6 km) into the crust beneath Axial Volcano, located at the intersection of the Juan de Fuca Ridge and Cobb-Eickelberg Hotspot. The geometry of the LAB is funnel-shaped, representing a magma assimilation front that is thermally-controlled. The morphology of the LAB, in combination with failure surfaces deep within Axial Volcano, highlights the focusing of hotspot- and mid-ocean spreading centre-related magmatism towards the centre of the volcano, controlling both eruption and hydrothermal processes, and the chemical composition of erupted lavas5. Our discovery of a funnel-shaped, crustal LAB suggests that thermally-controlled magma assimilation could be occurring along this surface at other volcanic systems such as Iceland.

Source: Nature

DOI: 10.1038/s41586-025-08865-8

Authors: G. M. Kent, A. F. Arnulf, S. C. Singh, H. Carton, A. J. Harding, S. Saustrup