Abstract
The geotherm in subduction zones is thought to vary as a function of the subduction rate and the age of the subducting lithosphere. Along a single subduction zone the rate of subduction may strongly vary due to changes in the angle between the trench and the plate convergence vector, i.e., the subduction obliquity, due to trench curvature. We currently observe such curvature in, e.g., the Marianas, Chile and Aleutian trenches. Recently, strong along-strike variations in subduction obliquity were proposed to have caused a major temperature contrast between Cretaceous geological records of western and central Turkey. We test here whether first-order temperature variation in a subduction zone may be caused by variation in the trench geometry using simple thermo-kinematic finite-element 3-D numerical models. We prescribe the trench geometry by means of a simple mathematical function and compute the mantle flow in the mantle wedge by solving the equation of mass and momentum conservation. We then solve the energy conservation equation until steady state is reached. We analyze the results (i) in terms of mantle wedge flow with emphasis on the trench-parallel component and (ii) in terms of temperature along the plate interface by means of maps and the depth-temperature path at the interface. In our experiments, the effect of the trench curvature on the geotherm is substantial. A small obliquity yields a small but not negligible trench-parallel mantle flow, leading to differences of 30 °C along-strike of the model. Advected heat causes such temperature variations (linked to the magnitude of the trench-parallel component of velocity). With increasing obliquity, the trench-parallel component of the velocity consequently increases and the temperature variation reaches 200°C along-strike. Finally, we discuss the implication of our simulations for the ubiquitous oblique systems that are observed on Earth and the limitations of our modeling approach. Lateral variations in plate sinking rate associated with curvature will further enhance this temperature contrast. We conclude that the synchronous metamorphic temperature contrast between central and western Turkey may well have resulted from reconstructed major variations in subduction obliquity.
| Original language | English |
|---|---|
| Pages (from-to) | 759-776 |
| Number of pages | 18 |
| Journal | Solid Earth |
| Volume | 9 |
| Issue number | 3 |
| DOIs | |
| Publication status | Published - 14 Jun 2018 |
Funding
Acknowledgements. We thank Luuk Schuurmans for investigating several aspects of the presented research. Riad Hassani is warmly thanked for his help with the implementation of the stabilized Q1Q1 finite-element formulation in ELEFANT. Alexis Plunder and Douwe J. J. van Hinsbergen were funded through ERC starting grant SINK (306810). Douwe J. J. van Hinsbergen acknowledges NWO Vidi grant 864.11.004. Alexis Plunder thanks Loes van Unnik Hoorn for tremendous discussions during his postdoc at Utrecht University and the preparation of this paper. The perceptually uniform color maps davos and vik were used in this study to prevent visual distortion of the data (http://www.fabiocrameri.ch/visualisation.php). Reviews by Manuele Faccenda and an anonymous reviewer were much appreciated and helped to strengthen the paper.
