Investigating subduction characteristics in eastern Iran using analogue modeling

Structural and petrological evidence suggests an asymmetric and two-sided subduction of the Sistan oceanic lithosphere under the Lut and Afghan blocks. The subduction under the Lut block was characterized by a steeper dip angle and a higher subduction rate, leading to the retreat of the plate boundary towards the ocean and subsequent back-arc extension. Studies on the geochemistry and possible origin of the mafic-intermediate igneous rocks of the Lut block corroborate the occurrence of crustal thinning and back-arc extension, highlighting the significant role of subduction in their formation. In this research, we employed laboratory or analog modeling with scale lengths to simulate the characteristics of the Sistan oceanic lithosphere subduction and the geodynamic processes in eastern Iran. We investigated the parameters controlling the style of subduction by examining the sinking of a thin viscoelastic silicone putty sheet with varying geometric and rheological properties in a glucose syrup-filled reservoir. Our findings revealed that an increase in length and thickness, coupled with a low viscosity ratio of the lithosphere and asthenosphere, accelerates the subduction rate. We also identified a significant correlation between the dip angle and the subduction rate. In summary, the deformation of the back-arc region was analyzed through kinematic investigation in the performed experiments. The experimental outcomes, which confirm the high rate and dip angle of subduction, and also the back-arc extension, can be identified as characteristics of the Sistan Ocean’s subduction zone under the Lut block.