From Fossil to Active Hydrothermal Outflow in the Back‐Arc of the Central Apennines (Zannone Island, Italy)

Abstract Post‐orogenic back‐arc magmatism is accompanied by hydrothermal ore deposits and mineralizations derived from mantle crustal sources. We investigate Zannone Island (ZI), Tyrrhenian basin, Italy, to define the source(s) of mineralizing fluids their relationships with regional petrological‐tectonic setting. On ZI, early Miocene thrusting was overprinted late post‐orogenic extension related alteration. Since active submarine outflow reported close island, provides an ideal site determine P ‐ T X evolution long‐lived system. combined field work microstructural analyses on syn‐tectonic quartz veins carbonate mineralizations, X‐ray diffraction analysis, microthermometry element mapping fluid inclusions (FIs), C, O, clumped isotopes, noble gases (He‐Ne‐Ar) CO 2 content in FIs. Our results document a system magmatic origin increasing mixing meteoric fluids. Magmatic were responsible for precipitation at ∼125 150 MPa ∼300°C–350°C. With onset extensional faulting, progressively interacted rocks mixed fluids, leading (a) host rock alteration associated minor mineral precipitation, (b) progressive neutralization, (c) cooling (from ∼320°C ∼86°C), (d) embrittlement fracturing rocks. Both show values lower than those adjacent volcanic areas systems, indicating that fossil‐to‐active history emplacement multiple intrusions.