青海湖QH1孔晚全新世沉积物稀土元素地球化学与气候环境关系探讨

通过对青海湖QH1孔沉积物稀土元素丰度分布模式及稀土总量(REE)的分析结合沉积物中TOC含量粒度参数的变化特征探讨了稀土元素纵向变化与气候环境之间的关系. 结果表明青海湖沉积物中稀土元素总丰度值不高平均值为63mg/kg不包括Y左右. 总体上表现以半干旱的环境为主导化学风化作用相对微弱. 同时湖泊沉积物具有轻稀土相对富集缓右倾斜型CeEu基本上无明显异常的REE分布模式. 稀土元素与总有机碳TOC粒度之间存在较好的相关性. 分析表明沉积物中REE高值段指示暖湿气候环境REE低值段代表冷干气候环境. 根据稀土元素分布与沉积环境的关系重建了8500aBP以来青海湖区经历4次较大的暖湿-温干-暖偏湿-冷偏干的气候演化过程. 从而得出在高寒半干旱地区的青海湖沉积物中稀土元素对古气候变化具有良好的指示作用.

Geochemistry of REE in QH1 Sediments of Qinghai Lake since Late Holocene and Its Paleoclimatic Significance

Rare earth element(REE) concentration and distribution patterns and vertical distribution of total REE(REE) in sediments from Qinghai Lake are presented in this paper. In combination with total organic carbon (TOC) and Grain Size parameters, the relationship between REE and the climate and environment has been discussed. The result shows that the REE values of the sediments from Qinghai Lake vary over a range of 16.262-89.221mg/kg, with an average of 63.001mg/kg. Indicating that the semi-arid environment was dominant with much weaker chemical weathering. The sediments from Qinghai Lake have very similar REE distribution patterns, which are moderately rich in light rare earth element (LREE), with negative slopes and unclear Ce and Eu anomaly. REE contents have good relationships with TOC and Grain Size. During warmer and wetter climatic episodes, the values of REE in sediments are higher; on the contrary, during colder and drier climatic episodes, the values of REE are lower. The further study has reconstructed the paleoclimate evolution of Qinghai Lake since 8.5kaBP, which includes four main climatic and environmental changes that were warm-moist, cool-dry, warm-moist and cold-dry during late Holocene. Finally, we have concluded that REE in sediments of Qinghai Lake is an effective indicator to reconstruct the paleoclimatic variation in the high-cold semi-arid areas because of its sensitivity to the climatic changes.