207Pb-206Pb, 40Ar-39Ar and Fission-Track Geothermochronology Quantifying Cooling and Exhumation History of the Kaman-Kırşehir Region Intrusions, Central Anatolia, Turkey

Abstract

The Kaman-Kirsehir region intrusions were generated in a post-collisional extensional setting following Cenomanian-Turonian docking of an oceanic island arc, comprising the supra-subduction zone (SSZ) Central Anatolian ophiolite (CAO), onto the Tauride-Anatolide Platform (TAP). These granitoids have been named, from N to S, the Camsari quartz syenite, Hamit quartz syenite, Bayindir nepheline-cancrinite syenite, Durmuslu nepheline-nosean-melanite syenite porphyry and Baranadag quartz monzonite. They intrude the crustal metasediments of the Central Anatolian Crystalline Complex (CACC) and CAO and are unconformably overlain by Upper Paleocene to Lower-Middle Eocene sediments. The single-zircon 207Pb-206Pb evaporation age of the Camsari unit is 95.7±5.1 Ma; those of the Hamit and Baranadag units are indistinguishable with a weighted mean of 74.3±4.5 Ma. The amphibole 40Ar-39Ar ages of the Hamit and Baranadag units are almost identical with a weighted mean of 72.7±0.1 Ma. The apatite fission-track age vs elevation plot for the Camsari, Hamit, Durmuslu and Baranadag samples reveals rapid exhumation (>1 km/Ma) between ~57 and ~61 Ma, consistent with the results of track-length modelling. This Early-Middle Paleocene rapid exhumation is thought to result from uplift triggered by continent (TAP) - continent (Eurasian plate; EP) collision following the closure of Izmir-Ankara-Erzincan (IAE) ocean that also initiated the formation of peripheral foreland basins in central Anatolia.