Age and Crystallization Duration of Alpine Fissure Monazite-(Ce) and Correlation with Tectonically-Driven Hydrothermal Dissolution-(Re)Precipitation Events

This study investigates deformation along the retrograde path of the Alps through in-situ Th-Pb dating of hydrothermal (or fissure) monazite-(Ce). Fissure monazite-(Ce) crystals are found in alpine-type fissures and crystallizes at relatively low temperatures (∼200 - 400 ̊C). The Th-Pb isotopic system of fissure monazite-(Ce) can only be disturbed by dissolution-(re)precipitation events due to chemical disequilibrium with the hydrothermal fluids, commonly induced by tectonic activity. Fissure monazite-(Ce) ages (i) corroborate existing chronological data, (ii) were completed with structural information in order to constrain tectonic movements associated with monazite-(Ce) crystallization, (iii) were used to attribute fluid inclusion data to different episodes of fissure formation. The combined data show that across the Alps monazite-(Ce) crystallization occurred episodically over 85 Ma. The oldest ages of ∼90 Ma were found in the Eastern Alps whereas younger ages, down to ∼5 Ma, were recorded towards the Central and Western Alps