西太平洋深海沉积物孔隙水稀土元素地球化学特征及 意义

为探索深海孔隙水中稀土元素的生物地球化学循环过程,对太平洋菲律宾海九州-帕劳海脊东、西两侧的两个钻孔沉积物进行了高精度的孔隙水采样工作,分析了主、微量元素和稀土元素的地球化学特征,并对稀土元素的浓度、配分模式以及分馏特征进行了详细的讨论。结果表明:这两个钻孔沉积物均处于氧化环境,表现出海水-沉积物界面和浅层孔隙水(2.5~20 cm)中相对富集轻稀土和中稀土,而中层(25~60 cm)和深层沉积物(>65 cm)孔隙水中则相对富集重稀土元素的特征。初步推断有机质和锰(氢)氧化物的分解和吸附作用是造成孔隙水中稀土元素分馏的主要因素。相比于九州-帕劳海脊的东、西两侧海域,孔隙水中的稀土元素浓度和分馏程度存在一定的差异,周围环境中的矿物组成和锰(氢)氧化物等是其主要的控制因素,但是研究区域深海孔隙流体并不能为海洋贡献稀土元素。

Rare earth element geochemistry characteristics and implications of pore-water from deep sea sediment in Western Pacific Ocean

In order to explore the biogeochemical process of the rare earth elements in deep sea pore water,high-precision samples were collected from the two stations of the Philippine Sea.Geochemical characteristics of the main elements,trace elements and REE are analyzed and the concentration,distribution and fractionation of the REE discussed in details.It is found that both the two stations are in an oxidizing environment.HREE and MREE are enriched around the water-sediment interface and in the shallow pore water(2.5~20 cm),while MREE and HREE enriched in the middle(25~60 cm)and lower layers of sediments.We believe that the decomposition and adsorption of organic matter and Mn oxide are the main factors for the fractionation of REE in pore water.Concentrations and fractionations of REE in pore water are found different in the East and West sides of the Kyushu Palau Ridge because of the difference in volcanic activities,mineral composition and Mn oxide in the surrounding environment.However,the pore fluid of the study area makes no contribution of REE to the ocean.