TITANITE AND ZIRCON FISSION-TRACK DATING RESOLVES SUCCESSIVE IGNEOUS EPISODES IN THE FORMATION OF THE COMPOSITE KAÇKAR BATHOLITH IN THE TURKISH EASTERN PONTIDES

Abstract

The Kaçkar batholith in the Turkish eastern Pontides comprises several intrusive units with distinctive textural, mineralogical and geochemical characteristics. Their titanite and zircon fission-track ages confirm that the different lithodem units result from consecutive igneous episodes, establish their emplacement sequence and, together with geochemical data, help to relate them to their geodynamic context. The Çamlıkaya granitoid (112.4±1.6Ma) was emplaced during an immature-arc magmatic episode of early Cretaceous age. The Sırtyayla (57.1±1.2Ma) and Marselevat (52.9±1.3Ma) granitoids are late products of a late-Palaeocene mature-arc episode. The Ayder granitoid (46.4±1.0Ma) is the result of middle- to late-Eocene post-collisional magmatism related to slab break-off. The Halkalıtaş quartz diorite (43.7±2.3Ma) and the Güllübağ monzonite (38.1±0.9Ma) document a middle- to late-Eocene episode related to post-collisional extension. The data reveal the advantages of dense sampling, spanning a maximum range of elevations. Apart from the increased precision on the mean, redundant sampling allows to shift the basis for interpretation from a priori assumptions to a posteriori numerical criteria when using geochronometers with low to moderate closure temperatures, including apatite, titanite and zircon fission-tracks but also K–Ar (Ar–Ar) biotite, muscovite and K-feldspar.