Extrusion of subducted crust explains the emplacement of far-travelled ophiolites

Abstract

Continental subduction below oceanic plates and associated emplacement of ophiolite sheets remain enigmatic chapters in global plate tectonics. Numerous ophiolite belts on Earth exhibit a far-travelled ophiolite sheet that is separated from its oceanic root by tectonic windows exposing continental crust, which experienced subduction-related high pressure-low temperature metamorphism during obduction. However, the link between continental subduction-exhumation dynamics and far-travelled ophiolite emplacement remains poorly understood. Here we combine data collected from ophiolite belts worldwide with thermo-mechanical simulations of continental subduction dynamics to show the causal link between the extrusion of subducted continental crust and the emplacement of far-travelled ophiolites. Our results reveal that buoyancy-driven extrusion of subducted crust triggers necking and breaking of the overriding oceanic upper plate. The broken-off piece of oceanic lithosphere is then transported on top of the continent along a flat thrust segment and becomes a far-travelled ophiolite sheet separated from its root by the extruded continental crust. Our results indicate that the extrusion of the subducted continental crust and the emplacement of far-travelled ophiolite sheets are inseparable processes.

Tectonic Evolution of the Nevado‐Filábride Complex (Sierra de Los Filábres, Southeastern Spain): Insights From New Structural and Geochronological Data

“…In this scenario, the Paleogene burial can be related to the obduction of an oceanic lithosphere connected with a hyper‐extended continental margin over the continental NFC. The obduction of oceanic lithosphere or arc‐continent collisions are commonly associated with regional burial metamorphism of continental margins (e.g., Agard & Vitale‐Brovarone, 2013; Goffé et al., 1988; Porkoláb et al., 2021; Pourteau et al., 2013; van Hinsbergen et al., 2016). In this scenario, the Paleogene white mica 40 Ar/ 39 Ar ages of the relic S 0‐1 foliation in the continental Calar‐Alto unit can be explained by burial metamorphism during the obduction of the Ophiolite unit (Figure 11c), whose record is preserved only in the deeper sections of the Calar‐Alto unit, at far distances from the Miocene shear zones (Figures 7a and 8g).…”

The forearc ophiolites of California (USA) formed during trench-parallel spreading: kinematic reconstruction of the western USA Cordillera since the Jurassic

“…Ophiolites not only contain records of spreading ridges, but also relics of subduction interfaces in the form of metamorphic soles (Guilmette C. et al, 2018;Hacker et al, 1996), as well as transform faults (Allerton, 1989;Morris and Maffione, 2016). But because ophiolites form and are uplifted at plate boundaries, they typically are dismembered, displaced, and eroded klippen that form the structurally highest thrust sheet in fold-thrust belts (e.g., Maffione et al, 2015;Porkoláb et al, 2021;Robertson, 2002). With rare exceptions such as in the Semail ophiolite of Oman that covers an area of more than 20,000 km 2 (Nicolas et al, 2000), the original coherence of these klippen as an ocean floor cannot be directly established from field observations.…”

Formation of Metamorphic Soles Underlying Ophiolites During Subduction Initiation: A Systematic Numerical Study

“…For example, using 2-D thermo-mechanical models, Duretz et al (2016) studied the obduction process of Oman ophiolite, which indicated that a thermal anomaly in the oceanic lithosphere near the continental margin along with a strong continental crust is required for the emplacement of the ophiolite. Moreover, Porkoláb et al (2021) studied the relationship between the subduction-exhumation process and emplacement of far-traveled ophiolite. They further proposed that extrusion of the subducted continental margin driven by buoyancy is critical, and controls the emplacement of far-traveled ophiolitic sheet.…”