Geochemistry and isotope composition (Sr, Pb, δ<sup>66</sup>Zn) of Vulcano fumaroles (Aeolian Islands, Italy)

Article Article scientifique Article Geochemistry and isotope composition (Sr, Pb, δ<sup>66</sup>Zn) of Vulcano fumaroles (Aeolian Islands, Italy) eng 2018 author Chiaradia Massimo 0000-0003-4943-2480 110575 author Pujol Sola Nuria 818953 author Farre De Pablo Julia 819597 author Aiuppa Alessandro author Paonita Antonio author Rizzo Andrea Luca author Brusca Lorenzo 10.1016/j.chemgeo.2018.05.038 0009-2541 http://linkinghub.elsevier.com/retrieve/pii/S0009254118302948 We present and discuss temperatures, major and trace element gas geochemistry, radiogenic isotopes (Pb, Sr) and the first Zn isotope data of fumarole condensates and altered rocks from the Vulcano fumarolic field. The fumaroles of the La Fossa cone, sampled on 5th May 2015, have temperatures ranging between 233 and 427 °C. They plot compositionally on the mixing trend between the magmatic and hydrothermal end-members defined by previous studies, but are strongly displaced towards the hydrothermal component. Correlations of radiogenic (Sr, Pb) and stable isotopes of Zn with δ13CCO2 and several trace elements of the fumarolic acid condensates support mixing between the above mentioned distinct (magmatic and hydrothermal) fluids. The magmatic end- member has a less radiogenic Sr (87Sr/86Sr ~0.7045) and heavier Zn isotope composition (δ66Zn ~0.3‰). The hydrothermal fluid end-member has a more radiogenic 87Sr/86Sr signature (> 0.7055), which could be due to leaching of radiogenic Sr from the crystalline basement rocks or reflect seawater Sr. It is also characterized by lighter Zn isotope composition (δ66Zn < −0.3), most likely reflecting equilibrium fractionation of Zn isotopes during precipitation of sphalerite (ZnS) from the hydrothermal fluid. Nonetheless, some scatter in the correlation trends suggests either the involvement of additional (subordinate) source(s) or temporal variations in isotopic and chemical compositions of the two above end-members. Pb isotope compositions of the fumaroles sampled in this study show a shift towards less radiogenic values compared to pre-2001 fumaroles. This could indicate either a change in the hydrothermal circulation pattern (leading to leaching of rocks with different isotopic compositions) or the involvement of a new, isotopically distinct, magmatic fluid. The alteration zones around the fumarole vents are also characterized by systematic correlations of Pb and Zn isotopes with major and trace elements. We interpret these as the result of the addition onto the substratum volcanic rock of Pb and Zn from the fumaroles. Zn isotope signatures of the alteration zones are significantly heavier than those of the corresponding fumaroles (δ66Zn = 0.3–1.6) probably due to equilibrium fractionation occurring during sphalerite precipitation at the vent discharge. Aeolian Islands Vulcano Island Volcanic gases Fumaroles Zinc isotopes Radiogenic isotopes Geochemistry Dewey 550 42 Département des sciences de la Terre 154 false 663 Isotope Geochemistry, Geochronology and Thermochronology 692 Mineral Resources and Geofluids Chemical Geology ca271cd3-4b67-45d6-a949-49239ccc164c Article (Published version) Restricted Chiaradia_CHEMGE_2018.pdf 2360174 application/pdf restrictedAccess Faculté des sciences / Section des sciences de la Terre et de l'Environnement / Département des sciences de la Terre

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Geochemistry and isotope composition (Sr, Pb, δ⁶⁶Zn) of Vulcano fumaroles (Aeolian Islands, Italy)	Chemical Geology			2018	554	2

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