Architecture and evolution of an extensionally-inverted thrust (Mt. Tancia Thrust, Central Apennines): geological, structural, geochemical, and K-Ar geochronological constraints

Fault inversion may lead to significant obliteration of earlier tectonic structures, thus preventing the straightforward interpretation of the complete kinematics and deformation history of faults. We adopt a multidisciplinary approach to: (1) reconstruct the tectonic evolution through space and in time of the extensionally-inverted Mt. Tancia Thrust (Central Apennines, Italy); (2) understand the deformation mechanisms and the transition and reactivation of compressional structures during negative tectonic inversion; and (3) constrain the origin of fluids involved during tectonic processes. To this end, we combined: (1) detailed geological mapping and multiscale structural analysis; (2) illite-smectite paleothermal indicators; (3) C, O, and clumped isotopes on calcite mineralizations and (4) K–Ar dating of authigenic and/or syn-kinematic illite from the Mt. Tancia Thrust fault rocks. We show that shortening occurred between ~9 and ~7 Ma, during possibly multiple events of fluid overpressure and shear rupturin