Publication Date:
2022-10-24
Description:
Post-orogenic back-arc magmatism is accompanied by hydrothermal ore deposits and
mineralizations derived from mantle and crustal sources. We investigate Zannone Island (ZI), back-arc
Tyrrhenian basin, Italy, to define the source(s) of mineralizing hydrothermal fluids and their relationships with
the regional petrological-tectonic setting. On ZI, early Miocene thrusting was overprinted by late Miocene
post-orogenic extension and related hydrothermal alteration. Since active submarine hydrothermal outflow is
reported close to the island, Zannone provides an ideal site to determine the P-T-X evolution of the long-lived
hydrothermal system. We combined field work with microstructural analyses on syn-tectonic quartz veins
and carbonate mineralizations, X-ray diffraction analysis, microthermometry and element mapping of fluid
inclusions (FIs), C, O, and clumped isotopes, and analyses of noble gases (He-Ne-Ar) and CO2 content
in FIs. Our results document the evolution of a fluid system of magmatic origin with increasing mixing
of meteoric fluids. Magmatic fluids were responsible for quartz veins precipitation at ∼125 to 150 MPa
and ∼300°C–350°C. With the onset of extensional faulting, magmatic fluids progressively interacted with
carbonate rocks and mixed with meteoric fluids, leading to (a) host rock alteration with associated carbonate
and minor ore mineral precipitation, (b) progressive fluid neutralization, (c) cooling of the hydrothermal
system (from ∼320°C to ∼86°C), and (d) embrittlement and fracturing of the host rocks. Both quartz and
carbonate mineralizations show noble gases values lower than those from the adjacent active volcanic areas and submarine hydrothermal systems, indicating that the fossil-to-active hydrothermal history is associated with the emplacement of multiple magmatic intrusions.
Description:
Published
Description:
e2022GC010474
Description:
1T. Struttura della Terra
Description:
2T. Deformazione crostale attiva
Description:
7T. Variazioni delle caratteristiche crostali e "precursori"
Description:
9T. Geochimica dei fluidi applicata allo studio e al monitoraggio di aree sismiche
Description:
2TR. Ricostruzione e modellazione della struttura crostale
Description:
JCR Journal
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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