Les isotopes du lithium: exemples d'applications en géochimie

Abstract : This manuscript is a summary of the research work carried out at BRGM over the past 10 years under my direction in the field of lithium isotope geochemistry. First, we describe in detail the protocol for measurement of lithium isotopes in liquid and solid matrices by MC-ICP-MS (Multi Collector Inductively Coupled Plasma Mass Spectrometer). This protocol requires validation of the entire analytical procedure. Then, we illustrate through various examples, the application of this isotopic tool in environmental systems such as rainwater and rivers, and during water/rock interactions at low and high temperature through the study of thermo-mineral and geothermal waters and finally in experimental systems. The main conclusions of this work are: 1/ the distribution of lithium and its isotopes in surface water (rain and rivers) is highly variable. Lithium in rain is in part derived from the oceans but other sources such as anthropogenic inputs and dust must be taken into account. 2/ Lithium in river waters is almost exclusively derived from the alteration of silicate rocks. The isotopic composition of lithium in river waters is a good tracer of the "weathering regime" which controls the balance between the dissolution of primary minerals and the precipitation of secondary minerals that can fractionate the lithium isotopic ratios of river waters by preferentially incorporating 6Li. 3/ The isotopic composition of lithium in thermo-mineral waters also shows great variation and 7/6Li of water is inversely correlated to the deep reservoir temperature. The thermo-dependence of the lithium isotopic fractionation between water and rock has been studied in both natural geothermal systems and with experimental approaches. Fractionation of lithium isotopes in hydrologic systems depends on the intensity of water/rock interactions both in terms of temperature in geothermal systems and "weathering regime" in surface waters. The common controlling mechanism of lithium isotope compositions is the balance between dissolution of primary minerals and formation of secondary minerals.
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Contributor : Romain Millot <>
Submitted on : Thursday, November 28, 2013 - 2:59:46 PM
Last modification on : Friday, May 10, 2019 - 1:54:15 PM

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Millot Romain. Les isotopes du lithium: exemples d'applications en géochimie. Sciences de la Terre. Université d'Orléans, 2013. ⟨tel-00910947⟩

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