Three-dimensional thermal structure of subduction zones: effects of obliquity and curvature

• Published in: Solid earth (Göttingen) Vol. 3; no. 2; pp. 365 - 373
• Main Authors: Bengtson, A. K, van Keken, P. E
• Format: Journal Article
• Language: English
• Published: Gottingen Copernicus GmbH 22.11.2012; Copernicus Publications
• Subjects: Analysis; Earth science; Subduction zones
• ISSN: 1869-9529; 1869-9510; 1869-9529
• DOI: 10.5194/se-3-365-2012

Quantifying the precise thermal structure of subduction zones is essential for understanding the nature of metamorphic dehydration reactions, arc volcanism, and intermediate depth seismicity. High resolution two-dimensional (2-D) models have shown that the rheology of the mantle wedge plays a critical role and establishes strong temperature gradients in the slab. The influence of three-dimensional (3-D) subduction zone geometry on thermal structure is however not yet well characterized. A common assumption for 2-D models is that the cross-section is taken normal to the strike of the trench with a corresponding velocity reduction in the case of oblique subduction, rather than taken parallel to velocity. A comparison between a full 3-D Cartesian model with oblique subduction and selected 2-D cross-sections demonstrates that the trench-normal cross-section provides a better reproduction of the slab thermal structure than the velocity-parallel cross-section. An exception is found in the case of a strongly curved trench, such as in the Marianas, where strong 3-D flow in the mantle wedge is generated. In this case it is shown that the full 3-D model should be evaluated for an accurate prediction of the slab thermal structure. The models demonstrate that the use of a dynamic slab and wedge, separated by a kinematic boundary, yields good results for describing slab velocities in 3-D.