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Chapter 11 : Noble gases and halogens in fluid inclusions : a journey through the Earth’s crust

by M. Kendrick and P.Burnard

The applications of noble gases in geological fluids can be considerably extended into deeper crustal environments and/or the geological past by the analysis of fluid inclusions. Fluid inclusions enable metamorphic and magmatic fluids to be sampled ; in some cases trapping occurs before atmospheric noble gases are introduced via mixing with surface-derived groundwater. The range of crustal fluids investigated for noble gases has recently been further expanded to include fluid inclusions formed during extensional deformation, and eclogite facies metamorphism relevant to subduction-recycling. As a result, fluid inclusions from ore deposits and metamorphic environments have greatly expanded the range of crustal fluid types investigated for noble gases. This chapter aims to illustrate : i) how the noble gas composition of fluid inclusions can help constrain the origin of the major volatile phases, such as H2O and CO2, in fluid inclusions, quantifying the presence of mantle and atmospheric components in crustal fluids ; and, ii) how additional insights on fluid origins and acquisition of salinity are provided by simultaneous analysis of the halogens (Cl, Br, I) using an approach which is an extension of the 40Ar-39Ar methodology, enabling noble gases to be more closely linked with other fluid tracers. Fluid inclusion studies are providing important new insights on the behaviour of noble gases in the crust. This is illustrated primarily through noble gas and halogen data that illuminate the diverse fluid processes responsible for ore deposition in a range of sedimentary, magmatic and metamorphic environments.


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Chapter 11

25 juillet 2012
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3.3 Mo