The olivine-ringwoodite transformation triggers deep slab seismicity and rheological weakening.
biomechanical · Level V
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- Record sourced from PubMed, PMID 41991545.
- Also identified by DOI 10.1038/s41467-026-71661-z.
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Abstract
The subducting cold oceanic plates (slabs) exhibit two paradoxical deformation behaviors: deep seismicity and rheological weakening within the mantle transition zone (MTZ, ~400-700 km depths). Although the transformation of metastable olivine wedge (MOW)<sup>1,2</sup> in cold slabs has been proposed as a possible trigger for both behaviors<sup>3-10</sup>, direct experimental evidence remains limited to understand the processes linking them. Here we report experimental results on the transformation-deformation coupling at MTZ pressures (~20 GPa). Ringwoodite is produced as nano-polycrystalline lamellae (NPL) under uniaxial stress. Thin NPL trigger unstable slips with coseismic stress drops by grain-size sensitive creep coupled with thermal instability at ~760-860 °C. Thickening of NPL at ~950-1,330 °C stabilizes the deformation with enhancing the transformation utilizing their incoherent nature. Thus, the formation of NPL and their grain-size sensitive creep play key roles in temperature-dependent transformation-deformation coupling, which explains both deep seismicity near the MOW and rheological weakening outside the MOW.