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Imaging magmatically induced tectonics at the East Pacific Rise 9º50'N

Milena Marjanović1,2, Jie Chen3, Javier Escartín3, Ross Parnell-Turner2 and Jyun-Nai Wu4

  • Affiliations: 1Institut de Physique du Globe de Paris, Université Paris Cité, CNRS UMR 7154, Paris 75005, France; 2Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92037; 3Laboratoire de Géologie, École Normale Supérieure/CNRS UMR 8538, L'université Paris Sciences & Lettres, Paris 75005, France; 4Department of Geology and Geophysics, Woods Hole Oceanographic Institution, Woods Hole, MA, USA.

  • Presentation type: Talk

  • Presentation time: Tuesday 08:45 - 09:00, Room R290

  • Programme No: 6.2.2

  • Theme 6 > Session 2

Abstract

Mid-ocean ridges, the longest volcanic chain that wraps around the globe in ~60,000 km, represent a natural laboratory to examine genetic relationships between the tectonic and magmatic processes and provide linkages between surface and subsurface observations at metric scales. Several submarine focus sites with well-developed magmatic systems, such as the East Pacific Rise (EPR) 9º50'N, are extensively studied. At this fast-spread center, faults within the axial summit trough (AST) are induced by vertically propagating dikes from the underlying magma body. Beyond the axial high (>2000 m), the formation of the faults is associated with the unbending of the lithosphere. A handful of inward-dipping faults are mapped between these thermally distinct zones, but their origin is poorly understood. This study uses an interdisciplinary approach, comparing unprecedented ultra-high-resolution 3-D seismic imagery and bathymetry data collected at the EPR. Our findings reveal a remarkable alignment between the distinct morphological features of magma bodies and steeply dipping faults. By directly comparing the architecture of a shallow emplaced magma body away from the AST and the geometry of the associated fault, we propose the mechanism for the fault unzipping; furthermore, we directly measure thermal anomaly along the fault and present the first images of potential magma pathways. The evident spatial link between tectonic and magmatic expressions in datasets and asymmetric fault nucleation mode argue for the most direct evidence for magmatically induced faulting, providing pathways for magma emplacement and hydrothermalism, with the lessons learned potentially transferrable to the volcanic systems operating on land.