Zn, Fe and S isotope fractionation in a large hydrothermal system

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Title: Zn, Fe and S isotope fractionation in a large hydrothermal system
Authors: Gagnevin, Damien
Boyce, Adrian
Barrie, Craig
Menuge, Julian
Blakeman, Robert
Permanent link: http://hdl.handle.net/10197/3869
Date: 1-Jul-2012
Online since: 2012-10-16T13:44:12Z
Abstract: The genesis of hydrothermal ore deposits is of crucial economic importance. This study investigates the extent, causes and consequences of zinc and iron isotope fractionation in a large hydrothermal system at the world-class Navan Zn–Pb orebody, Ireland. Large variations in Zn, Fe and S isotope compositions have been measured in microdrilled sphalerite (ZnS) at the millimetre scale. d66Zn and d56Fe display a well-defined positive correlation and both also correlate with d34S. These relationships represent the combined effects of kinetic Zn and Fe isotope fractionation during sphalerite precipitation, and S isotope variation through mixing of hot, metal-rich hydrothermal fluids and cool, bacteriogenic sulfide-bearing brines. Combined with S isotope data, d56Fe and d66Zn data on mine concentrates confirm that hydrothermal sulfide is a minor component of the overall deposit signature. Our data suggest that incoming pulses of metal-rich hydrothermal fluid triggered sulfide mineralisation, and that rapid precipitation of sphalerite from hydrothermal fluids will lead to strong kinetic fractionation of Zn and Fe isotopes at very short time and length scales, thereby limiting the use of Fe and Zn isotopes as exploration tools within deposits, but revealing the possibility of detecting new deposits from isotopically heavy Zn–Fe geochemical halos.
Funding Details: Science Foundation Ireland
Type of material: Journal Article
Publisher: Elsevier
Journal: Geochimica et Cosmochimica Acta
Volume: 88
Start page: 183
End page: 198
Copyright (published version): 2012 Elsevier Ltd
Keywords: Zn isotopesFe isotopesS isotopesIrish-typeIrelandZn-PbHydrothermalOreCarbonate-hostedBase metal
Subject LCSH: Zinc--Isotopes
Hydrothermal deposits--Ireland
DOI: 10.1016/j.gca.2012.04.031
Language: en
Status of Item: Peer reviewed
Appears in Collections:Earth Sciences Research Collection
Earth Institute Research Collection

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