Mesozoic intraoceanic subduction shaped the lower mantle beneath the East Pacific Rise

Area of Science:

• Geophysics
• Seismology
• Earth Sciences

Background:

• The Pacific large low-shear-velocity province (LLSVP) exhibits internal anomalies, including a significant structural gap between its central and eastern regions.
• The origin of this structural gap within the Pacific LLSVP remains poorly understood.

Purpose of the Study:

• To investigate the cause of the structural gap in the Pacific LLSVP.
• To understand the relationship between deep Earth structures and surface geological phenomena.

Main Methods:

• Analysis of global tomographic models to identify the Pacific LLSVP and its anomalies.
• Utilizing a dense array of SS precursors to image seismic velocity structures.
• Interpreting seismic velocity anomalies in the context of mantle phase transitions and temperature variations.

Main Results:

• An anomalously thick mantle transition zone was identified directly above the structural gap, east of the East Pacific Rise.
• This region shows faster-than-average seismic velocities, indicative of perturbed postolivine phase boundaries.
• The observations are attributed to Mesozoic-aged intraoceanic subduction beneath the Nazca Plate.

Conclusions:

• Ancient oceanic subduction played a role in separating the eastern Pacific LLSVP via downwelling.
• This study establishes a link between deep mantle structures, such as the Pacific LLSVP, and historical subduction events.
• The findings offer a novel perspective on the dynamic interplay between Earth's deep interior and surface tectonics.