Lithium and strontium isotopic compositions of sediments and pore waters at ODP Sites 152-918 and 152-919

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 NH4+ 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. […]

本文报道了格陵兰岛近海伊尔明厄海盆（Irminger Basin）内大洋钻探计划（Ocean Drilling Program，ODP）918与919站位，海底以下1157米深度范围内孔隙水（pore waters）中锂同位素（Li isotopes）的分布特征。本次研究在获取锂同位素数据的同时，还同步测定了锶同位素比值（strontium isotope ratios），以解析该沉积物体系中的成岩作用（diagenetic reactions）过程——该沉积物普遍赋存火山物质（volcanic material），且上层沉积段具备极高的沉积速率（accumulation rates）。87Sr/86Sr比值低于同期海水（contemporaneous seawater）值的现象，指示存在多处火山物质蚀变（volcanic material alteration）带。锂同位素剖面（Li isotope profiles）结构复杂，表明其与固相（solid phases）发生了多种交换反应（exchange reactions），包括与铵离子（NH4+）的阳离子交换（cation exchange）、深部沉积物中锂的活化迁移，以及火山物质的蚀变作用。因此，锂同位素可作为沉积物-水相互作用（sediment-water interaction）的灵敏示踪指标。[…]