Numerical modeling of exhumation of high pressure - low temperature metamorphic rocks: a case study of Tavsanlı and Afyon zone in western Anatolia

Abstract

Despite many numerical modeling works on burial and exhumation of crustal rocks, the formation of metamorphic rocks in High Pressure / Low Temperature (HP/LT) region and mechanism of their exhumation are poorly constrained. The metamorphic rocks in Tavsanli and Afyon Zone have high P/T ratios and they are represented by blueschist and greenschist to blueschist transitional rocks, respectively. The mechanism of burial and exhumation of crustal rocks were investigated by performing numerical experiments such as subduction of oceanic plate under the continental margin, intra-oceanic subduction and post-collision. Rheological constraints on exhumation of HP/LT rocks are presented. The numerical modelling results for subduction settings indicate that lithospheric mantle deforming in viscous rheology is the key factor to preserve the temperature of buried crustal rocks in subduction channel, whereas continental lithospheric mantle deforming in frictional plastic rheology gives metamorphic rocks in higher pressures and temperatures. The weaker crust and viscous rheology imposed in continental lithospheric mantle provides metamorphic rocks with P-T conditions comparable to Tavsanli Zone; strong crust and viscous rheology in continental lithospheric mantle gives metamorphic rocks with P-T conditions in agreement with Afyon Zone. In post-collision setting, the numerical modelling results show that weaker crust with high Moho temperature are the necessary conditions for exhumation of crustal rocks in high temperature / high pressure region.