3D slab breakoff in laboratory experiments

• Published in: Tectonophysics Vol. 773; p. 228223
• Main Authors: Fernández-García, Carlos, Guillaume, Benjamin, Brun, Jean-Pierre
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 20.12.2019; Elsevier BV; Elsevier
• Subjects: Analogue modelling; Continental subduction; Depth; Earth Sciences; Laboratories; Laboratory experiments; Ocean surface topography; Oceanic trenches; Passive margin; Passive margins; Sciences of the Universe; Slab breakoff; Subduction; Subduction (geology); Subduction zones; Tectonics; Topography; Topography (geology); Slab breakoff; Continental subduction; Analogue modelling; Passive margin; Topography
• ISSN: 0040-1951; 1879-3266
• DOI: 10.1016/j.tecto.2019.228223

•Slab breakoff occurs almost synchronously in a narrow range of depths when the passive margin is parallel to the trench.•Slab breakoff may occur over a wide range of depths and times in models with variable geometries for the oceanic to continental transition zone.•Phases of uplift and subsidence result from dynamic and isostatic adjustments associated with the lateral propagation of breakoff at depth. We study slab breakoff of subducting plates with variable orientations of passive margins (ocean-continent transition: OCT) using three-dimensional laboratory experiments. Our results show that the initial obliquity of the OCT with the trench determines the depth and timing of slab breakoff. The reference model involves a straight OCT parallel to the trench. Slab breakoff first starts in the central section of the subduction zone at a depth equivalent to ∼250km and then propagates rapidly towards the edges of the subduction zone where it develops at slightly higher depths (∼280km). In the models where passive margin arrives first at the edges of the subduction zone, slab breakoff starts at that location and propagates laterally towards the center of the subduction zone. It results in higher slab breakoff depths at the edges of the subduction zone than at the center (maximum difference of 170km). In models where the passive margin arrives first in the center of the subduction zone, slab-breakoff starts at that location and propagates towards the edges of the subduction zone over a period that can be as large as 31 Ma and with a large range of depths (maximum difference of 170km). The rate of lateral propagation of slab breakoff decreases with the increasing initial obliquity of the OCT with the trench. The model with the maximum obliquity shows a correlation between the surface topography and the slab breakoff at depth. The plate surface is uplifted after the oceanic and continental slab segments are mechanically decoupled, and in the final stage of the experiment, when the slab is educted, subsidence develops as the isostatic and dynamic support diminish.