Subduction Duration and Slab Dip

Abstract

The dip angles of slabs are among the clearest characteristics of subduction zones, but the factors that control them remain obscure. Here, slab dip angles and subduction parameters, including subduction duration, the nature of the overriding plate, slab age, and convergence rate, are determined for 153 transects along subduction zones for the present day. We present a comprehensive tabulation of subduction duration based on isotopic ages of arc initiation and stratigraphic, structural, plate tectonic and seismic indicators of subduction initiation. We present two ages for subduction zones, a long-term age and a reinitiation age. Using cross correlation and multivariate regression, we find that (1) subduction duration is the primary parameter controlling slab dips with slabs tending to have shallower dips at subduction zones that have been in existence longer; (2) the long-term age of subduction duration better explains variation of shallow dip than reinitiation age; (3) overriding plate nature could influence shallow dip angle, where slabs below continents tend to have shallower dips; (4) slab age contributes to slab dip, with younger slabs having steeper shallow dips; and (5) the relations between slab dip and subduction parameters are depth dependent, where the ability of subduction duration and overriding plate nature to explain observed variation decreases with depth. The analysis emphasizes the importance of subduction history and the long-term regional state of a subduction zone in determining slab dip and is consistent with mechanical models of subduction.

Subduction Dynamics and Mantle Pressure: 2. Towards a Global Understanding of Slab Dip and Upper Mantle Circulation

“…Deep slab dips (~300‐km depth) do not appear to correlate strongly with regional subduction parameters (e.g., Cruciani et al, 2005; Jarrard, 1986; Lallemand et al, 2005); there is no deep slab dip correlation with slab age (buoyancy) (Figure 1b) and a relatively minor correlation with convergence rate (Figure 1c) and absolute upper plate velocity. Interestingly, shallow slab dips exhibit an inverse correlation with subduction duration (Hu & Gurnis, 2020; Jarrard, 1986) and overriding plate thickness/type (e.g., Holt, Buffett et al, 2015; Hu & Gurnis, 2020), but these correlations do not persist to the deep slab depths considered here. It is therefore reasonable to ask whether global‐scale mantle flow plays a significant role in controlling deep slab dip.…”

Petrochronology of Wadi Tayin Metamorphic Sole Metasediment, With Implications for the Thermal and Tectonic Evolution of the Samail Ophiolite (Oman/UAE)

“…Coupled with data from adjacent rocks (Hacker & Mosenfelder, 1996), our new thermobarometric results nominally support this interpretation: within the top 12 m of Wadi Tayin sole, peak metamorphic conditions spatially transition from 800–900°C and 11–13 kbar (Cowan et al, 2014; Soret et al, 2017) to 665 ± 32°C and 7.5 ± 1.2 kbar (Figure 6). If this pressure is assumed to have been lithostatic, this implies ~15 km of missing and/or condensed section; given that most shallow subduction zones have dips on the order of 20–25° (Hu & Gurnis, 2020), this implies materials derived from ~40 km apart on a subducting slab. We note that the peak P‐T changes documented by Hacker and Mosenfelder (1996) occur downsection through amphibolites with roughly similar major‐element bulk compositions (Ishikawa et al, 2005), suggesting that sole rocks with common protoliths may have undergone a range of P–T paths.…”

Formation of East Asian Stagnant Slabs Due To a Pressure‐Driven Cenozoic Mantle Wind Following Mesozoic Subduction

“…The fourth one is the trench retreat, commonly attributed as an important reason for slab stagnation (Christensen, 1996; van der Hilst & Seno, 1993;Zhong & Gurnis, 1995). Some recent studies suggest the potential role of former subduction (Hu & Gurnis, 2020;Liu et al, 2021), but the dynamic nature remains elusive. There is still no systematic evaluation of these effects using a data-driven thermal-chemical modeling framework.East Asia is an ideal location for studying subduction dynamics and slab stagnation.…”