De Lange, G. J.

Haeckel, Matthias

Hensen, Christian

Liebetrau, Volker

Meixner, A.

Reitz, Anja

Romer, R. L.

Scholz, Florian

English

OceanRep

Geophysical Research AbstractsVol. 12, EGU2010-4251, 2010EGU General Assembly 2010© Author(s) 2010Lithium isotope systematics of deep-sourced pore fluids at continentalmarginsFlorian Scholz (1), Christian Hensen (1), Gert J. De Lange (2), Matthias Haeckel (1), Volker Liebtrau (1), AnetteMeixner (3), Anja Reitz (1), and Rolf L. Romer (3)(1) IFM-GEOMAR, Biogeochemistry, Kiel, Germany (fscholz@ifm-geomar.de), (2) Department of Earth Sciences, UtrechtUniversity, The Netherlands, (3) Deutsches Geoforschungszentrum GFZ, GermanyIn the past two decades, the behavior of lithium (Li) isotopes has been studied in various marine systems, includ-ing mid-ocean ridge and sediment-hosted hydrothermal systems, subduction zone settings and normal coastal anddeep-sea sediments recovered by the Ocean Drilling Program (ODP). Major processes identified to cause devia-tions from the seawater isotopic composition are adsorption/desorption reactions, formation and transformation ofsilicate minerals, and leaching of Li from sediments or underlying crust at high temperature. As a result of theaccomplished work, Li isotopes are considered a promising tracer for the diagenetic evolution and provenance ofpore fluids in overpressured sedimentary environments.Here, we present Li concentration and isotope data of 18 cold seep locations and reference fluids from shallow ma-rine sediments, a sediment-hosted hydrothermal system and two Mediterranean brine basins. The new referencedata and literature data of hydrothermal fluids and pore fluids from the ODP follow an empirical relationship re-flecting increasing Li release and decreasing isotope fractionation during clay mineral authigenesis with increasingtemperature. Lithium concentration and isotope data of cold seep fluids are mostly in agreement with this empir-ical relationship. Ubiquitous diagenetic signals of clay dehydration in all cold seep fluids indicate that authigenicsmectite-illite is an important sink for light pore water Li in deeply buried continental margin sediments. Devi-ations from the general relationship are attributed to the varying proportion of weatherable (e.g. volcanogenic)components and to transport-related fractionation trends. A simple transport-reaction model was applied to simu-late Li isotope fractionation during upwelling of pore fluids to the seafloor. It is demonstrated that slow pore wateradvection (order of mm a−1) suffices to convey much of the deep-seated diagenetic Li signal into shallow sedi-ments. If carefully applied, Li isotope systematics may, thus, provide a valuable record of fluid/mineral interactionthat has been inherited several hundreds or thousands of meters below the seafloor.

Lithium isotope systematics of deep-sourced pore fluids at continental margins

Lithium isotope systematics of deep-sourced pore fluids at continental margins

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