Terrane accretion explains thin and hot ocean-continent back-arcs

Area of Science:

• Geophysics and Tectonics
• Earth Sciences
• Geodynamics

Background:

• Hot ocean-continent back-arc regions exhibit enigmatic characteristics: thin mantle lithosphere and high surface heat flow.
• Existing explanations, such as mantle lithosphere removal or back-arc extension, are insufficient or lack clear causal mechanisms for widespread thinning.
• Many such systems share a history of terrane accretion, a factor often overlooked in previous models.

Purpose of the Study:

• To investigate the role of terrane accretion in explaining the formation of hot ocean-continent back-arc regions.
• To test the hypothesis that terrane accretion can account for the observed thin mantle lithosphere and high heat flow.
• To provide a unified explanation for the key features of these enigmatic geological settings.

Main Methods:

• Utilized advanced thermomechanical model experiments to simulate geological processes.
• Focused on modeling the effects of terrane accretion within ocean-continent subduction systems.
• Compared model outcomes with observational data from real-world geological settings.

Main Results:

• Thermomechanical models demonstrate that terrane accretion consistently explains the observed characteristics of hot back-arc regions.
• Terrane accretion naturally leads to the development of rheologically weak back-arcs.
• This process results in continental crust positioned directly above hot sublithospheric mantle.

Conclusions:

• Terrane accretion offers a robust and unifying explanation for the enigmatic features of hot ocean-continent back-arc regions.
• The proposed mechanism resolves the limitations of previous theories involving mantle removal or insufficient back-arc extension.
• This finding highlights the critical importance of accretionary processes in shaping subduction zone geodynamics.