Distribution of hydrous minerals in the subduction system beneath Mexico

Abstract

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Seismic properties of the Nazca oceanic crust in southern Peruvian subduction system

“…Then, we discuss (1) processes of the low-velocity (shear) deformation zone near the plate interface, and (2) the role of water in mantle, in changing rheological and seismological properties, and subduction dynamics in southern Peru. We discuss these points by comparing with Mexico subduction zone system, which involve the slab-dip transition between flat and normal subduction (Kim et al, 2010(Kim et al, , 2012b(Kim et al, , 2013.…”

“…More recently, a presence of a low-viscosity channel atop the subducting crust is invoked by numerical calculations to support the current flat-slab configuration in central Mexico (Manea and Gurnis, 2007). The abundant occurrence of the mantle-derived minerals in the present-day subduction system probably would indicate that the mantle wedge had high H 2 O concentration due to the dehydration of subducted sediments and oceanic crust, and that the mantle peridotite would react with slab fluids to form serpentinite (Kim et al, 2013). Kim et al (2012b) further suggest that the central Mexican flat slab region is more hydrous than the region in south where the slab is dipping normal.…”

“…Scattered coda of teleseismic P waves, such as in receiver functions, often show a thin low-velocity layer corresponding to the top of the subducting plate. These have been best documented in Mexico (Kim et al, 2010(Kim et al, , 2012a(Kim et al, , 2013, Alaska (Kim et al, 2014), and Cascadia (Hansen et al, 2012), where a 2-4 km Fig. 2.…”

“…In the case for central Mexican flat subduction, some parts of the LVZ at ∼45 km depth correspond to anomalously low Vs (2.4-3.4 km/s) and thus higher Vp/Vs (up to 2.1) and Poisson's ratio (Kim et al, 2010). Such lower Vs indicate that a top portion of the flat slab is hydrous, and the presence of frictionally weak phases such as serpentine and talc in the LVZ may reduce tectonic coupling between overriding and subducting plates (Kim et al, 2010(Kim et al, , 2012b(Kim et al, , 2013. The evidence of high H 2 O content near the flat interface in southern Peru may originate from the subducting ridge and/or subduction channel.…”

“…The South-American westward absolute plate motion (van Hunan et al, 2002) may be an important effect for the creation of the Peruvian flat slab. In addition, considering an enigmatic case of the flat subduction in Mexico, the changes in the subduction dynamics through a change in mantle wedge viscosity by the slab dehydration process should be taken into account (Manea and Gurnis, 2007;Kim et al, 2013).…”