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Slab window
In geology, a slab window is a gap that forms in a subducted oceanic plate when a mid-ocean ridge meets with a subduction zone and plate divergence and convergence continue, causing the ridge to be subducted. 〔Thorkelson, Derek J., 1996, Subduction of diverging plates and the principles of slab window formation: Tectonophysics v. 255, p. 47-63 〕 Formation of a slab window produces an area where the crust of the over-riding plate is lacking a rigid lithospheric mantle component and thus is exposed to hot asthenospheric mantle (for a diagram of this, see the link below). This produces anomalous thermal, chemical and physical effects in the mantle that can dramatically change the over-riding plate by interrupting the established tectonic and magmatic regimes. 〔 In general, the data used to identify possible slab windows comes from seismic tomography and heat flow studies.〔van Wijk, J.W., Govers, R., Furlong, K.P., 2001, Three-dimensional thermal modeling of the California upper mantle: a slab window vs. stalled slab: Earth and Planetary Letters v. 186, p. 175-186〕
== Effects ==
As a slab window develops, the mantle in that region becomes increasingly hot and dry. The decrease in hydration causes arc volcanism to diminish or stop entirely, as magma production in subduction zones generally results from hydration of the mantle wedge due to de-watering of the subducting slab. Slab-window magmatism may then replace this melting, and can be produced by multiple processes, including increased temperatures, mantle circulation producing interaction of supra- and sub-slab mantle, partial melting of subducted slab edges and extension in the upper plate. 〔 Mantle flowing upward through the slab window in order to compensate for the decreased lithospheric volume can also produce decompression melting. Slab window melts are distinguished from calc-alkaline subduction-related magmas by their different chemical compositions.
The increase in temperature caused by the presence of a slab window can also produce anomalous high temperature metamorphism in the region between the trench and the volcanic arc.〔Groome, Wesley G., Thorkelson, Derek J., 2009, The three-dimensional thermo-mechanical signature of ridge subduction and slab window migration: Tectonophysics v. 464, p. 70-83〕
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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