On the Evolution and Fate of Sediment Diapirs in Subduction Zones

Abstract

Subduction of sedimentary material, combined with subduction erosion, is the dominant mechanism for returning differentiated continental material to Earth's mantle (Clift et al., 2009;Scholl & von Huene, 2007). The modern flux of crustal material to the mantle is estimated to be of the same order of magnitude as the present rate of continental addition at subduction zones (Clift et al., 2009), and at some convergent boundaries may outpace the addition of new continental material.The presence of sedimentary material in both modern and ancient exposed accretionary complexes and subduction interfaces (

Himalayan zircons resurface in Sumatran arc volcanoes through sediment recycling

“…Transfer of the subducted sediments into the mantle wedge could occur through diapirism that the sediments rise buoyantly from the slab surface and partially melt in the hot corner of the mantle wedge 13,14,60 . According to thermodynamic modeling, dehydration melting is unlikely to occur in most sediment compositions at typical slab-top conditions and diapir formation is directly related to sediment thickness and composition, and the thermal state of the subduction zone 61 . Sediment diapir in the northern Sumatra subduction zone probably initiates at ~70 km depth with a temperature slightly higher than 500 °C13 .…”

“…According to the calculated sediment diapir trajectories 60 and the thermal structure of the Sumatran subduction zone 57 , the temperature (<800 °C) of the sediment diapir trajectory from the slab surface at ~150 km depth would first increase to >1200 °C at ~100 km depth in the mantle wedge and then decrease to <800 °C at Moho 60 . Melting of sediment diapirs started from the surface inwards and may not obtain equilibrium under P-T conditions above the sediments' liquidus 60,61 . As such, the subducted Nicobar Fan sediments, which have undergone dehydration and eclogitization, would partially melt during ascent (Fig.…”

“…Numerical modeling indicates that sediment diapirs ascending through the mantle wedge beneath the volcanic arc would undergo less than ~40-50% total melting 60,61 . Because (1) the relict mineral phases and their proportions change along the P-T path of the sediment diapir trajectory, (2) melt and the relict mineral phases may not achieve equilibrium at each depth (temperature), and (3) mantle metasomatism occurs during ascending of the Si-rich sediment melts, the compositions of the 87 Sr/ 86 Sr compositions that can be explained by either crustal contamination or sediment addition.…”

Formation of Continental Crust by Diapiric Melting of Recycled Crustal Materials in the Mantle Wedge

“…A marked feature of HMS arcs compared with LMS arcs is that large volumes of crustal materials are subducting, including eroded forearc crust in the Andes CVZ (Goss et al., 2013; Stern, 1991) and TMVB (Parolari et al., 2018), the Emperor seamount in the N. Kamchatka (Nishizawa et al., 2017), and the Cocos Ridge in the SE Central America (Gazel et al., 2015, 2019). Thermodynamic models reveal that subduction of large volumes of low‐density material favors mélange diapirism (Klein & Behn, 2021).…”

Trench topography in subduction zones: A reflection of the plate decoupling depth

“…Although it is difficult to accurately measure the MDD in natural subduction zones (Syracuse et al, 2010), several studies have provided their estimates from indirect proxies, for example, the maximum depth of non-reworked colder subducting crusts (low velocity layers) using high-resolution tomographic images. Compilation of various available estimates yields the MDD in a range of 60-80 km (Wada and Wang, 2009;Abers et al, 2020), whereas cold slabs (Izu Bonin) can develop the deepest decoupling by sediment transport up to 120 km depth (Klein and Behn, 2021).…”