The peridotite ridge province in the southern Iberia Abyssal Plain: Seismic constraints revisited

The west Iberia margin has become the type example of a magma-starved margin in which extension during breakup led to the exhumation of mantle rocks apparently over a broad area. Much of our understanding of this process is based on geophysical and drilling data from the southern Iberia Abyssal Plain, where the seaward part of the region of exhumed mantle is comprised of a series of margin-parallel basement ridges. Here we analyse wide-angle and normal incidence seismic data from a series of intersecting profiles across this peridotite ridge province and develop a three-dimensional picture of its structure. Using these seismic data, we infer a location and age (magnetic anomaly M1; 125-127?Ma) of first-formed oceanic crust in this region that are consistent with Ocean Drilling Program data and data from the conjugate margin. We infer that the peridotite ridge province is about 70?km wide with strong serpentinization (>75%) at the top of basement reducing to much lower degrees (< 25%) around 2?km below. We map the geometry of some prominent reflectors on the landward margin of the peridotite ridge province that likely represent detachment faults and show that one of these has a domal structure similar to that of detachment faults at slow- to ultra-slow-spreading mid-ocean ridges.

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