Lithium isotope geochemistry of pore waters from ocean drilling program Sites 918 and 919, Irminger Basin

The distribution of Li isotopes in pore waters to a depth of 1157 m below seafloor is presented for ODP Sites 918 and 919 in the Irminger Basin, offshore Greenland. Lithium isotope data are accompanied by strontium isotope ratios to decipher diagenetic reactions in the sediments which are characteri...

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Bibliographic Details
Published in:Geochimica et cosmochimica acta 1998-07, Vol.62 (14), p.2437-2450
Main Authors: Zhang, Libo, Chan, Lui-Heung, Gieskes, Joris M
Format: Article
Language:English
Subjects:
Marine
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Summary:The distribution of Li isotopes in pore waters to a depth of 1157 m below seafloor is presented for ODP Sites 918 and 919 in the Irminger Basin, offshore Greenland. Lithium isotope data are accompanied by strontium isotope ratios to decipher diagenetic reactions in the sediments which are characterized by the pervasive presence of volcanic material, as well as by very high accumulation rates in the upper section. The lowering of the 87Sr/ 86Sr ratio below contemporaneous seawater values indicates several zones of volcanic material alteration. The Li isotope profiles are complex suggesting a variety of exchange reactions with the solid phases. These include cation exchange with NH 4 + and mobilization from sediments at depth, in addition to the alteration of volcanic matter. Lithium isotopes are, therefore, a sensitive indicator of sediment-water interaction. δ 6Li values of pore waters at these two sites vary between −42 and −25 ‰. At shallow depths (
ISSN:0016-7037
1872-9533
DOI:10.1016/S0016-7037(98)00178-1