WTMP – Magmatic Evolution and Metallogeny of Subduction to Post-Subduction Magmas in Anatolia, Turkey (WTMP Phase 1)

Thesis

Late Cenozoic post-subduction tectonic, magmatic and metallogenic evolution of the Anatolide-Tauride Orogenic Belt, Turkey

Fabien Rabyrol, PhD, 2018

Abstract: The termination of the northward subduction of the Southern Neotethyan oceanic slab beneath the Anatolide-Tauride Block in Turkey led to the onset of the Arabia-Eurasia continental collision in the Oligocene. The subducting Southern Neotethyan slab was affected by post-subduction segmentation manifested by slab break-off (central-eastern Anatolia) and tearing (western Anatolia) during the late Cenozoic. Many igneous complexes formed in the late Cenozoic and some of them host gold-rich porphyry and epithermal prospects and deposits. New temporal (U-Pb, ⁴⁰Ar/³⁹Ar and Re-Os dates), spatial (field observations and GIS) and geochemical data (elemental and Sr-Nd-Pb isotopic analyses) provide robust constraints on the genetic relationship between late Cenozoic slab segmentation tectonic events, Anatolian magmatism and associated gold mineralization. The newly-defined Eastern Anatolian Magmatic Belt formed in response to the slab break-off initiation at ca. 25 Ma, window opening, westward break-off propagation to central Anatolia and induced asthenospheric flow. The slab break-off-related igneous units were subsequently covered by widespread volcanic products in eastern Anatolia (12 Ma – Present) that resulted from the long-lived asthenospheric heating, destabilization of the thickened Anatolian lithosphere root and its partial removal by convective dripping. Magmatic sources include the shallow melting of the previously-metasomatized Anatolian subcontinental lithospheric mantle and asthenosphere by decompression due to impingement of the Arabian and African sub-slab asthenospheric mantles. Late Cenozoic Anatolian magmatism produced porphyry and epithermal prospects and deposits that cluster in nine isolated mineral districts controlled by graben, transtensional corridors and pull-apart basins. The bulk of gold mineralization (33 Moz Au) peaked at the beginning of the slab break-off event at 25 Ma in central and eastern Anatolia, and slab tear at 15 Ma in western Anatolia. The late Cenozoic trench-parallel and -perpendicular migrations of slab rupture and window opening in Anatolia 1) allowed toroidal and poloidal flow of asthenosphere beneath Anatolia, 2) caused the migration of melting source and associated igneous complexes and mineral deposits in the overriding crust, 3) destabilized the Anatolian lithospheric mantle, which reduced the amount of available volatiles and metals, and therefore 4) increased the production of barren, drier and mantle-dominant volcanism through time that partially covers fertile igneous units.