Link between crustal thickness and Moho transition zone at 9°N East Pacific Rise

Abstract

Oceanic crust is formed from basaltic melt produced by decompression melting due to mantle upwelling at mid-ocean ridges. This crust is separated from the underlying mantle either by a sharp Mohorovičić (Moho) discontinuity or a thick Moho transition zone (MTZ). Determining the relationship between the oceanic crustal structure and the MTZ is critical for understanding the crustal accretion processes at mid-ocean ridges. However, this relationship remains elusive due to the lack of high-resolution velocity model of the oceanic crust and MTZ. Here, we present result from the application of full waveform inversion to wide-angle seismic data acquired over a young oceanic crust near the 9°N East Pacific Rise, allowing us to obtain the crustal and MTZ thicknesses along a ∼70 km-long segment. We find that the crustal thickness and the MTZ thickness vary along the segment and they are inversely correlated, although the total cumulative thickness does not vary much along the profile. These variations could be attributed to the different melt migration efficiency or the variations in mantle thermal/chemical structure, indicating mantle heterogeneity along the ridge.