کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
6433748 | 1636754 | 2014 | 10 صفحه PDF | دانلود رایگان |
- Calculation of a 2D metamorphic density model of a subduction zone.
- Investigation of the impact of hydration, partial melting and fractionation on density.
- Comparing the buoyancy of the subducted crust and subducted lithospheric mantle.
- Contribution of eclogitization to slab pull is overestimated at the early stages.
- Lithosphere densification makes higher contribution to slab pull at the early stages.
Understanding the relationships between density and spatio-thermal variations at convergent plate boundaries is important for deciphering the present-day dynamics and evolution of subduction zones. In particular, the interaction between densification due to mineralogical phase transitions and slab pull forces is subject to ongoing investigations. We have developed a two-dimensional subduction zone model that is based on thermodynamic equilibrium assemblage calculations and includes the effects of melting processes on the density distribution in the lithosphere. Our model calculates the “metamorphic density” of rocks as a function of pressure, temperature and chemical composition in a subduction zone down to 250Â km. We have used this model to show how the hydration, dehydration, partial melting and fractionation processes of rocks all influence the metamorphic density and greatly depend on the temperature field within the subduction system. These processes are largely neglected by other approaches that reproduce the density distribution within this complex tectonic setting. Our model demonstrates that the initiation of eclogitization (i.e., when crustal rocks reach higher densities than the ambient mantle) of the slab is not the only significant process that makes the descending slab denser and generates the slab pull force. Instead, the densification of the lithospheric mantle of the sinking slab starts earlier than eclogitization and contributes significantly to slab pull in the early stages of subduction. Accordingly, the complex metamorphic structure of the slab and the mantle wedge has an important impact on the development of subduction zones.
Journal: Tectonophysics - Volume 637, 10 December 2014, Pages 20-29