Deformation and surface uplift associated with serpentinization at mid-ocean ridges and subduction zones

Abstract

[1] We employ the classical problem of an inclusion in an elastic half-space to model effects of sub-surface serpentinization on crustal deformation, change of stress state, and surface uplift. At the TAG hydrothermal field on the Mid-Atlantic Ridge, the model suggests that an anomalous salient 3 km in diameter and 100 m high that projects 3.5 km westward from the east valley wall may have resulted from a relatively deep-seated well-serpentinized body exhibiting transformational strain. The associated large strains would likely result in sub-surface fracturing or faulting, but surface uplift may be relatively insensitive to the exact depth and shape of the serpentinized region. Serpentinization of a region beneath the footwall of the TAG detachment fault will tend to promote slip along some overlying normal faults, which may then enhance fluid pathways to the deeper crust to continue the serpentinization process. Our solution for the Miyazaki Plain above the Kyushu-Palau subduction zone in SW Japan explains the observed uplift of ≈120 m. The small transformational strains associated with serpentinization in this region may promote thrust-type events in the aseismic slip zone near the upper boundary of the subducting Philippine Sea Plate as well as intraplate earthquakes associated with normal faulting. The rate of serpentinization needed to produce the observed uplift at the Miyazaki Plain is significantly greater than that needed at TAG, though significantly smaller on per unit volume basis. Thermal effects of serpentinization in both regions appear to be small, but uplift data provide an additional constraint on inferring serpentinization from geological and seismological observations. © 2012. American Geophysical Union.