Four‐dimensional numerical modeling of crustal growth at active continental margins

Abstract

[1] Crustal growth and topography development in subduction-related arcs are intimately related to magmatic processes and melt production above subducting slabs. Lateral and temporal variations in crustal thickness and composition have been observed in nature, but until now no integrated approach has been developed to comprehensively understand magmatic activity in subduction-related arcs. Here we investigate the 4-D spatial, temporal, and compositional character of continental crustal growth at active margins using a new 4-D (space-time) petrological-thermomechanical numerical model of a subduction-related magmatic arc. Based on a series of numerical experiments, we demonstrate that crustal growth inside the arc is inherently clustered in both space and time. The characteristic wavelength of variations in crustal thickness and topography along the arc is on the order of 30-80 km and is comparable to volcano clustering in natural arcs. The clusters of new crust are formed mainly by basaltic melt episodically extracted from partially molten peridotite due to lateral variation of water release and transport in the mantle wedge. Melts derived from subducted oceanic crust and sediments could contribute up to 15-50 vol% to the arc crust growth and their relative proportion is maximal at the onset of subduction. The total amount of newly formed crust correlates mainly with the amount of convergence since the beginning of subduction and is not strongly influenced by the plate convergence velocity. Indeed, slower subduction and lower melt extraction efficiency helps partially molten sediments and oceanic crust to be transported into the mantle wedge by hydrated, partially molten diapiric structures. For the modeled regime of stable subduction, the maximum crustal additional rate (25-40 km 3 /km/Myr) occurs when the amount of convergence reaches around 700 km. Mantle wedge structures developed in our models correlate well with available geophysical (seismological) observations for the Alaskan subduction zone. In particular, partially molten mantle plumes found in our models could explain low seismic anomalies in the mantle wedge, whereas mobile water and water release patterns could reflect paths and sources for magmatic activity evidenced by seismic b-value and Vp/Vs ratio analysis.

The role of magmatically driven lithospheric thickening on arc front migration

“…Given these limitations, we do not attempt a systematic fit to all data in Figure . Future steps toward quantitative modeling of data should include arc‐specific constraints on the magnitude and spatial distribution of tectonic forcing [ Oncken et al ., ; Stern et al ., ], which will necessitate a more complete numerical treatment of mantle flow, melting and heat transfer [e.g., Zhu et al ., ]. Modeling of geochemical proxies for thickening including xenolith studies [ Mantle and Collins , ; Chin et al ., ], and of crustal thickness [ Allmendinger et al ., ; Heit et al ., ; Calvert et al ., ] may also better constrain‐specific subduction histories.…”

Regimes of subduction and lithospheric dynamics in the Precambrian: 3D thermomechanical modelling

“…The models have been carried out with the 3D numerical I3ELVIS code (Gerya and Yuen, 2007) which is based on a conservative finite difference method with a multigrid solver and a non-diffusive marker-in-cell technique to simulate multiphase flow (Gerya andYuen, 2003, 2007). Additionally, the 3D code also features melting of crustal and mantle rocks and volcanic addition of primordial crust from silicate melt, eclogitic phase changes as well as hydration and dehydration (Zhu et al, 2013).…”

The contribution of metamorphic petrology to understanding lithosphere evolution and geodynamics

“…Geodynamic modeling has been used to address important processes such as slab breakoff (Gerya et al, 2004;Duretz et al, 2011), shallow subduction (van Hunen et al, 2004;Currie and Beaumont, 2011), ridge subduction (Groome and Thorkelson, 2009), deep crustal flow (Royden et al, 1997;Clark and Royden, 2000;Beaumont et al, 2004), delamination (Gray and Pysklywec, 2012;Ueda et al, 2012), intraplate orogenesis (Neil and Houseman, 1999;Pysklywec and Beaumont, 2004;Gorczyk et al, 2012Gorczyk et al, , 2013Gorczyk and Vogt, 2014), and exhumation of UHPM terranes (Gerya et al, 2002;Warren et al, 2008;Beaumont et al, 2009;Sizova et al, 2012). Geodynamic modeling has also been used to evaluate crustal growth at active continental margins (Vogt et al, 2012;Zhu et al, 2013) and to understand the links between metamorphism and tectonics (Jamieson and Beaumont, 1988;Sandiford and Powell, 1990;Jamieson et al, 2002Jamieson et al, , 2004Gerya and Stockhert, 2006;Li et al, 2010). Of course, geodynamic modeling has also been applied to the problem of Precambrian geodynamics (van Thienen et al, 2004;van Hunen and van den Berg, 2008;Sizova et al, 2010Sizova et al, , 2014Gerya, 2014;Johnson et al, 2014) and tectonics (Perchuk and , and the formation of the cratonic roots composed of strongly depleted sub-continental mantle lithosphere (Gray and Pysklywec, 2010;…”