Syn-tectonic supradetachment travertines (Gediz Basin, Western Anatolia)

Travertine deposits are valuable archives of tectonic and hydrothermal processes in geothermal areas, commonly associated with high-angle normal and/or strike-slip faults. In this paper we document the first case of syn-tectonic travertine deposition associated with a low-angle extensional detachment: the Alaşehir detachment, in the southern margin of the Gediz supra-detachment Basin, western Anatolia. The travertine directly overlies the detachment surface and is locally cut by low-angle faults kinematically compatible with the detachment, indicating carbonate precipitation during the late brittle activity of the detachment system. Structural data show that travertine formation was controlled by the interaction between the detachment and steep transtensional to strike-slip transfer faults. Based on kinematics, orientation and vein distribution, these faults are interpreted as the main vertical conduits for carbonate-rich fluids, whereas the detachment and associated fractures promoted lateral fluid migration where hydraulically connected. This interpretation is supported by fault–vein relationships, banded calcite/aragonite veins and stable-isotope signatures indicating meteoric-derived waters charged with deep inorganic carbon. U–Th geochronology constrains the youngest reliable travertine deposition and feeder-vein activity between ca. 600 and 400 ka, whereas samples beyond the dating range suggest earlier hydrothermal activity. We introduce the term supra-detachment travertine (SupTra) for travertine deposits genetically associated with low-angle detachment faulting in highly extended continental crust. SupTra deposits expand the known tectonic settings of travertine formation and provide a new archive of coupled deformation, permeability evolution, fluid flow and carbonate precipitation during the late evolution of highly extended continental crust.