EGU25-14179, updated on 15 Mar 2025
https://doi.org/10.5194/egusphere-egu25-14179
EGU General Assembly 2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
Ponded Melt-Rich Zone at the Base of Lithospheric Plate in Central Mariana Revealed Using Ocean Bottom Seismometer Data
Jiahui Zhang1,2 and Xin Wang1,2
Jiahui Zhang and Xin Wang
  • 1Chinese Academy of Sciences, Institute of Geology and Geophysics, China (zjh15230067544@163.com)
  • 2University of Chinese Academy of Sciences,College of Earth and Planetary Sciences, China

    The Mariana subduction zone, with its relatively simple oceanic subduction structure and water-rich environment, serves as a unique natural laboratory for studying mantle hydration processes and the lithosphere-asthenosphere boundary (LAB). In this study, we analyze passive-source Ocean Bottom Seismometer data from stations deployed across both the forearc and incoming plate regions to investigate the S-wave velocity structure beneath the central Mariana region. By extracting multi-frequency teleseismic receiver functions and surface wave dispersion data, and applying a transdimensional Bayesian joint inversion method that explicitly accounts for water-layer effects, we achieve a high-resolution characterization of the lithospheric subsurface structure. Our findings confirm significant mantle hydration, consistent with previous studies, and reveal a distinct low-velocity zone at the LAB. Unlike conventional passive-seismic studies, which typically describe the LAB as a single sharp velocity reduction, our results indicate a rapid velocity decrease followed by an equally sharp increase, delineating a ~10 km thick melt-rich zone. Our findings highlight the importance of treating the LAB as a complex system rather than a simple boundary, as the melt-rich zone acts as a lubricant, significantly reducing viscosity and facilitating decoupling of the lithosphere from the asthenosphere, thus enabling plate motion.

How to cite: Zhang, J. and Wang, X.: Ponded Melt-Rich Zone at the Base of Lithospheric Plate in Central Mariana Revealed Using Ocean Bottom Seismometer Data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14179, https://doi.org/10.5194/egusphere-egu25-14179, 2025.