Subduction of trench-fill sediments beneath an accretionary wedge: Insights from sandbox analogue experiments

Atsushi Noda, Hiroaki Koge, Yasuhiro Yamada, Ayumu Miyakawa, Juichiro Ashi

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)

Abstract

Sandy trench-fill sediments at accretionary margins are commonly scraped off at the frontal wedge and rarely subducted to the depth of high-pressure (HP) metamorphism. However, some ancient exhumed accretionary complexes are associated with high-pressure-low-temperature (HP-LT) metamorphic rocks, such as psammitic schists, which are derived from sandy trench-fill sediments. This study used sandbox analogue experiments to investigate the role of seafloor topography in the transport of trench-fill sediments to depth during subduction. We conducted two different types of experiments, with or without a rigid topographic high (representing a seamount). We used an undeformable backstop that was unfixed to the side wall of the apparatus to allow a seamount to be subducted beneath the overriding plate. In experiments without a seamount, progressive thickening of the accretionary wedge pushed the backstop down, leading to a stepping down of the decollement, narrowing of the subduction channel, and underplating of the wedge with subducting sediment. In contrast, in experiments with a topographic high, the subduction of the topographic high raised the backstop, leading to a stepping up of the decollement and widening of the subduction channel. These results suggest that the subduction of stiff topographic relief beneath an inflexible overriding plate might enable trench-fill sediments to be deeply subducted and to become the protoliths of HP-LT metamorphic rocks.

Original languageEnglish
Pages (from-to)1664-1679
Number of pages16
JournalGeosphere
Volume16
Issue number4
DOIs
Publication statusPublished - 2020
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Geology
  • Stratigraphy

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