Tectonic burial and exhumation cycles tracked by muscovite and K-feldspar 40Ar/39Ar thermochronology in a strike-slip fault zone, central Turkey

Abstract

Muscovite and K-feldspar 40 Ar/ 39 Ar ages from the eastern margin of the Niğde massif in central Anatolia track the timing of initial exhumation, reburial, and final exhumation and cooling of metamorphic rocks deformed within a strike-slip fault zone. Although the ages of initial and final cooling were known from previous studies, our new results document the timing of the reheating/reburial event. Muscovite from four of eight gneiss samples have Late Cretaceous 40 Ar/ 39 Ar ages that date initial cooling at ~ 75 Ma. The remaining samples have perturbed spectra that climb to Late Cretaceous ages with increasing extraction temperatures during analysis. These perturbed samples are located beneath a faulted unconformity overlain by Paleogene sedimentary deposits that were derived in part from the metamorphic rocks, then buried, metamorphosed, and deformed under greenschist facies conditions. Samples close to the faulted unconformity are more perturbed than structurally deeper samples. The age of the thermal perturbation is determined at 30 ± 5 Ma using multi-diffusion domain modeling of K-feldspar 40 Ar/ 39 Ar data from two gneiss samples, one located close to the unconformity and one at a structurally deeper level. Muscovite 40 Ar/ 39 Ar results and modeled K-feldspar temperature–time histories show that the eastern margin of the Niğde massif experienced a reheating event that peaked at ~ 30 Ma. The thermal pulse has been attributed to reburial associated with transpression in the Ecemiş segment of the Central Anatolian Fault Zone along the eastern margin of the Niğde massif. Activity of this fault zone may represent a far-field expression of the onset of collision of Arabia with Eurasia in SE Anatolia. • The Niğde massif, Turkey, experienced two cycles of burial and exhumation. • K-feldspar MDD Ar modeling predicts peak of reburial and reheating at ~ 30 Ma. • Reburial/reheating may have been response of central Anatolia to incipient Arabia–Eurasia collision.