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Smithsonite is a secondary zinc carbonate mineral that is one of the key components of zinc ore bodies. In nature, it is commonly formed via its precursor phase hydrozincite by (i) the reaction with a carbonate source or by (ii) precipitation of zinc salt solutions with a CO2-saturated and bicarbonate-rich solution. Smithsonite may be used in respect to isotope proxies to calculate transformation temperatures. However, this is not straight forward as (trans-) formation occurs via a precursor phase and is dependent on pCO2. Theoretical calculation demonstrated that Zn isotope fractionation between fluid and precipitating solid is temperature dependent. Thus, knowledge about the Zn isotope composition could constitute a potential temperature proxy. In order to investigate this hypothesis, a pilot study was conducted based on previous experimental work in which smithsonite was precipitated at varying temperatures yet constant pCO2. In these experiments, formation of smithsonite was induced by the transformation of hydrozincite at 25, 40, 60 and 80 °C. Preliminary results of the solids reveal a temperature dependent fractionation (Δ66Znsmith-H2O = δ66ZnSmith - δ66ZnH2O) between 25 and 80°C. This contribution invites discussions about potential mechanisms producing Zn isotope fractionation in smithsonite.
|Publication status||Submitted - 23 Nov 2018|