Seismic evidence of a complex multi-lens melt reservoir beneath the 9° N Overlapping Spreading Center at the East Pacific Rise

A. F. Arnulf (1) , S. C. Singh (1) , J. W. Pye

1 IPGP - Institut de Physique du Globe de Paris

The crustal structure at fast spreading ridges is characterized by the presence of an axial melt lens along a significant part of the ridge axis over a partially molten lower crust. Using three-dimensional seismic reflection data and waveform inversion, here we show the existence of two to three stacked melt lenses beneath both limbs of the 9°N overlapping spreading center on the East Pacific Rise, which we suggest are the source of the very evolved lavas locally observed on the seafloor. The melt lenses are 2-4 km wide and lie in a 900 m depth range. We suggest that the presence of a complex multi-lens melt reservoir in the crust is due to the reduced ambient stress regime, hence cracking, resulting from the overlap of the two segments of the ridge, allowing melt to stay longer in the crust at different depths.

Keywords: melt lens; axial magma chamber; mid-ocean ridges; East Pacific Rise; seismic reflection; waveform inversion

Domains: Sciences of the Universe [physics]

A. F. Arnulf, S. C. Singh, J. W. Pye. Seismic evidence of a complex multi-lens melt reservoir beneath the 9° N Overlapping Spreading Center at the East Pacific Rise. Geophysical Research Letters, 2014, 41, pp.6109-6115. ⟨10.1002/2014GL060859⟩. ⟨insu-03581102⟩