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Evidence of magmatically induced faults at the East Pacific Rise

By comparison of ultra-high-resolution 3-D seismic imagery and bathymetry data collected at the East Pacific Rise (EPR) 9º50'N, researchers reveal the existence of magmatic induced faults near the ridge axis.

Evidence of magmatically induced faults at the East Pacific Rise

Publication date: 25/06/2024

Press, Research

Related teams :
Marine Geosciences

At fast-spreading centers, faults develop within the axial summit trough (AST), representing the innermost accretionary zone (0-250 m from the axis). These faults are primarily induced by dikes vertically propagation from the axial magma lens (AML – Pocket of magmatic liquid and crystals below the axis). Beyond the axial high (>2000 m), the formation of the observed faults is associated with the unbending of the lithosphere as it cools and spreads away from the AST. Between these two thermally distinct zones, where the lithosphere is still too hot for the faults to be linked with the process of thermal cooling but too far for the reach of the accretional diking process dominating the ridge axis, faults are mapped, but their origin is poorly understood.

Schematic view of one such magmatically induced fault.
3-D bathymetry of the seafloor at the East Pacific Rise 9ºN showing the three dominant faulting mechanisms: diking within the innermost axial zone (Fa), flexural bending (Ff) and magmatically induced (F). The inset represents a bathymetric close-up of the studied region with a well-developed axial summit trough at 1 m resolution.
The shape of magma bodies (in pink) is superimposed on the gray-shaded bathymetry for three distinct regions. The geometry of the faults’ traces in the seafloor (extent marked by black arrows) remarkably matches the morphology of the magma bodies, suggesting a strong genetic tectono-magmatic relationship.

By comparison of ultra-high-resolution 3-D seismic imagery and bathymetry data collected at the East Pacific Rise (EPR) 9º50’N, researchers reveal a remarkable vertical alignment between the distinct morphological features of the magma body located at depth and the orientation of these inward-facing faults. The mapped faults’ spatial coincidence and asymmetric nucleation mode represent the most direct evidence for magmatically induced faulting near the ridge axis, providing pathways for hydrothermalism and magma emplacement, helping to build the crust outside of the AST. The high-resolution seafloor and subsurface images also enable revised tectonic strain estimates, showing that the near-axis tectonic component of seafloor spreading at the EPR is much smaller than previously thought.

3-D view of the axial magma lens from high-resolution seismic data collected at the East Pacific Rise. The inset represents a close-up emphasizing the main axial magma lens (AML), and the upper crustal off-axis magma lens (uOAML).

Read more

M. Marjanović, J. Chen, J. Escartín, R. Parnell-Turner, J-N. Wu, Magma-induced tectonics at the East Pacific Rise 9°50’N: Evidence from high-resolution characterization of seafloor and subseafloor, Proceedings of the National Academy of Sciences, Vol. 121 (25), e2401440121, DOI: 10.1073/pnas.2401440121

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