Timescales for the growth of sediment diapirs in subduction zones
Miller, Nathaniel C.
Behn, Mark D.
MetadataShow full item record
KeywordNumerical approximations and analysis; Subduction zone processes; Dynamics of lithosphere and mantle; Mechanics, theory, and modelling; Diapir and diapirism
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.
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.
Showing items related by title, author, creator and subject.
Seismic reflection imaging of the Juan de Fuca plate from ridge to trench : new constraints on the distribution of faulting and evolution of the crust prior to subduction Han, Shuoshuo; Carbotte, Suzanne M.; Canales, Juan Pablo; Nedimovic, Mladen R.; Carton, Hélène; Gibson, James C.; Horning, Greg W. (John Wiley & Sons, 2016-03-21)We present prestack time-migrated multichannel seismic images along two cross-plate transects from the Juan de Fuca (JdF) Ridge to the Cascadia deformation front (DF) offshore Oregon and Washington from which we characterize ...
The Subduction experiment : mooring field program and data summary ; Sub 1 June 1991-February 1992 ; Sub 2 February 1992-October 1992 ; Sub 3 October 1992-June 1993 Brink, Nancy J.; Moyer, Kerry A.; Trask, Richard P.; Weller, Robert A. (Woods Hole Oceanographic Institution, 1995-06)An array of five surface moorings carrying meteorological and oceanographic instrumentation was deployed for a period of two years beginning in June 1991 as part of an Office of Naval Research (ONR) funded Subduction ...
Draut, Amy E.; Clift, Peter D. (Geological Society of London, 2002)Dalradian meta-sediments of the Laurentian margin and mafic intrusions thereof in SW Connemara, Ireland, tectonically overlie meta-rhyolites of the Delaney Dome Formation. The two units are separated by the Mannin Thrust. ...