Timescales for the growth of sediment diapirs in subduction zones


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dc.contributor.author Miller, Nathaniel C.
dc.contributor.author Behn, Mark D.
dc.date.accessioned 2012-10-01T16:47:35Z
dc.date.available 2012-10-01T16:47:35Z
dc.date.issued 2012-07-10
dc.identifier.citation Geophysical Journal International 190 (2012): 1361–1377 en_US
dc.identifier.uri http://hdl.handle.net/1912/5406
dc.description Author Posting. © The Author(s), 2012. This article is posted here by permission of John Wiley & Sons for personal use, not for redistribution. The definitive version was published in Geophysical Journal International 190 (2012): 1361–1377, doi:10.1111/j.1365-246X.2012.05565.x. en_US
dc.description.abstract In this study, we calculate timescales for the growth of gravitational instabilities forming in the sediment layer on the downgoing slab at subduction zones. Subducted metasediments are buoyant with respect to the overlying mantle and may form diapirs that detach from the slab and rise upwards into the mantle wedge. We use a particle-in-cell, finite-difference method to calculate growth rates for instabilities forming within a buoyant, wet-quartz metasediment layer underlying a dense mantle half-space composed of wet olivine. These growth rates are used to determine where sediment diapirs initiate and detach from the slab over a range of subduction zone thermal structures. We find that, given a sufficient layer thickness (200–800 m, depending on slab-surface and mantle-wedge temperatures), sediment diapirs begin to grow rapidly at depths of ∼80 km and detach from the slab within 1–3 Myr at temperatures ≤900 °C and at depths roughly corresponding to the location of the slab beneath the arc. Diapir growth is most sensitive to absolute slab temperature, however it is also affected by the viscosity ratio between the sediment layer and the mantle wedge and the length-scale over which viscosity decays above the slab. These secondary affects are most pronounced in colder subduction systems with old slabs and faster subduction rates. For a broad range of subduction zone thermal conditions, we find that diapirs can efficiently transport sediments into the mantle wedge, where they would melt and be incorporated into arc magmas. Thus, we conclude that sediment diapirism is a common feature of many subduction zones, providing a potential explanation for the ‘sediment signature’ in the chemistry of arc magmas. en_US
dc.description.sponsorship This work was supported by NSF Grant EAR-0652707 and a WHOI Deep Ocean Exploration Institute Fellowship to MB. en_US
dc.format.mimetype application/pdf
dc.language.iso en_US en_US
dc.publisher John Wiley & Sons en_US
dc.relation.uri http://dx.doi.org/10.1111/j.1365-246X.2012.05565.x
dc.subject Numerical approximations and analysis en_US
dc.subject Subduction zone processes en_US
dc.subject Dynamics of lithosphere and mantle en_US
dc.subject Mechanics, theory, and modelling en_US
dc.subject Diapir and diapirism en_US
dc.title Timescales for the growth of sediment diapirs in subduction zones en_US
dc.type Article en_US
dc.identifier.doi 10.1111/j.1365-246X.2012.05565.x

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