|Title:||Relationships between very high pressure subduction complex assemblages and intrusive granitoids in the Tavsanli Zone, Sivrihisar Massif, central Anatolia|
|Authors:||T. A. Shin, E. J. Catlos, L. Jacob, and K. Black|
|Publication:||Tectonophysics, v. , p. .|
The Sivrihisar Massif of central Anatolia exposes blueschist and eclogite facies metasedimentary and metabasaltic rocks in close association with granitoid plutons. The massif is located within the Tavsanli Zone, the subducted and exhumed northern continental margin of the Anatolide–Tauride Block. The relationship of the very high pressure assemblages to coexisting granitoid plutonic bodies (Kaymaz and Sivrihisar) is unclear as the region can be considered the type locality for the entrainment of excess argon in K‐bearing minerals. Samples from its granitoids and a subduction complex assemblage were collected, imaged with cathodoluminescence (CL), and dated using zircon U‐Pb in situ (in thin section) ion microprobe methods. The granitoids are heterogeneous as evidenced by CL images and geochemical variations. Finer‐grained Sivrihisar samples are syenite and show plagioclase replacing Kfeldspar, whereas coarser‐grained rocks are monzonite and show the opposite reaction. Our samples of the Kaymaz granitoids are extremely Si rich ( 82‐97 wt% SiO2) and have experienced sericitization. CL images of both granitoids show evidence for fluid interactions at both the subsolidus and lower temperature stages in their tectonic history. Subduction along the Tavsanli Zone was ongoing during the Early to Late Cretaceous and entrained zircons with igneous zonation in CL that crystallized as early as the Paleoproterozoic. Sivrihisar Massif granitoids record zircon crystallization from the Late Cretaceous to Early Oligocene. Here we present a model in which the Sivrihisar and Kaymaz melts source from a subducting slab along the Afyon Zone further to the south and mix with an igneous component generated during decompression due to break off of the Tavsanli slab. The model speculates that the Tavsanli Zone is the northernmost segment of an amalgamation of stacked subduction zones that transition in activity from north to south over time.