莱州湾07钻孔沉积物晚更新世以来的元素地球化学特征

在莱州湾南岸的07孔岩心进行高分辨率采样的基础上,采用X荧光光谱法(XRF)、离子质谱法(ICP-MS)以及原子荧光光谱法(AF)等方法测试了研究区07孔的48种常微量元素以及稀土元素的含量,并对元素相对含量、随深度变化规律、特征比值以及稀土元素配分模式进行了研究。结果表明,07孔主要元素及特征比值在海陆地层分界处有明显变化,可以作为地层划分的指标之一。其中,Mn、Mg、Ca、Fe、Mg/Ca及K/Na等对沉积环境响应比较明显,Ba、Zr、Rb、Si/A1、Ti/A1和Rb/Sr对源区的母岩类型、风化程度及搬运距离的变化敏感;07孔常微量元素垂向变化较大,在3次海侵地层中呈明显变化,并对应多个峰值。化学元素的变化规律所反映的地层特征与晚更新世以来的气候和海平面的变化有较好的对应关系。07孔不同深度沉积物的稀土元素球粒陨石标准化配分模式与黄河沉积物的相似,呈轻稀土元素富集的右倾型。说明黄河是莱州湾南岸弥河-潍河多源河流三角洲沉积体系的物源之一,且对莱州湾南岸一定深度范围内的沉积地层有部分贡献。

Geochemical characteristics of sediment in core 07 since the late Pleistocene in Laizhou Bay

Forty eight geochemical indexs of sediment samples,including major element,trace element and rare earth element(REE) content,were analyzed by X-ray fluorescence spectrometry (XRF),ion-coupled plasma-mass spectroscopy(ICP-MS) and atomic fluorescence spectrometry (AF) for the samples of core 07 obtained in the southern coast of Laizhou Bay. Meanwhile,the elements content,changing law,the characteristic ratio and distribution patterns of REE were studied. According to research,most elements and characteristic ratios in borehole 07 changed obviously in marine-continental stratigraphic boundaries,which could be used to divide stratum. In addition,Mn,Mg,Ca,Fe,Mg/Ca and K/Na were well correlated with sedimentary environment changes; Ba,Zr,Rb,Si/A1,Ti/A1 and Rb/Sr could be utilized to trace the type of source rock,weathering degree and the transport distance. Majority elements showed multi-cycle variation,especially in the transgression layers. The stratigraphic features reflected by the changes in chemical elements were well corresponding to climatic and sea-level changes since the late Pleistocene. The Chondrite-normalized REE distribution patterns of sediments in borehole 07 with different depth were similar to that Yellow River,and the LREE content was much higher than HREE,which indicated that Yellow River was one of provenances of Mihe-WeiHe multi-source fluvial delta sedimentary system in the south of Laizhou Bay,contributing to sedimentary strata within a certain range of depth.