哈拉湖岩芯XRF扫描元素统计分析及其环境意义

Statistical Analysis of XRF Scanned Elements and Their Environmental Significance in Hala Lake,Qinghai,China

中文关键词:  哈拉湖  XRF岩芯扫描分析  元素地球化学  环境意义

英文关键词:Hala Lake  XRF core scanning  Element geochemistry  Environmental significance

中文摘要:

      青藏高原东北缘高山湖泊哈拉湖是位于季风与西风影响的交汇带的封闭深水湖泊,是区域环境和气候变化的良好记录载体。目前对该湖的研究还较少,缺乏对沉积物中元素环境意义的系统认识。通过高分辨率XRF岩芯扫描,用相关、聚类和因子分析的方法对哈拉湖沉积岩芯地球化学元素进行分析。结果显示Ti、K、Si、Al、Fe、Mn等元素变化一致,相关性高,归为同一类,即径流输入的陆源碎屑组分,反映了流域水文状况如径流量的变化。Sr、Zr元素相关性高,为赋存在粗颗粒沉积物中的元素,根据哈拉湖实际,应为冬季湖泊冰面风力搬运,反映了湖区冬季风力强度的变化。Ca元素既与径流输入元素总体变化一致,也与Sr、Zr元素显著相关,且在第一和第二主成分(径流和风力)上的载荷相当,表明哈拉湖沉积物中的碳酸盐既有粗颗粒的外源碎屑,也有湖泊自生的组分,这在利用碳酸盐进行地球化学研究时应重视,注意去除外源碎屑碳酸盐的影响。可溶元素S和Cl可能反映了入湖水量与蒸发对比情况,与湖泊盐度有关。

英文摘要:

      :Hala Lake is a deep enclosed alpine lake in NE Tibetan Plateau which is in the transitional zone of the Asian Summer Monsoon and the westerlies.Continuous sediments preserved in this lake provide excellent materials for reconstructing regional environmental and climatic changes.However,a systematic knowledge on the sedimentary elements in this lake is still lacking due to few studies have been done.Here we present a multivariate statistical analysis on geochemical elements of Core HL13D from Hala Lake by high-resolution XRF scanning.Correlation analysis,cluster analysis and discriminant factor analysis were applied to the elements to reveal the geochemical significance of Ti,K,Si,Al,Fe,Mn,Ca,Sr,Zr and Cl elements preserved in the core.Results suggest that Ti,K,Si,Al,Fe and Mn elements have the same variations with a high correlation,representing the terrigenous clasts input and reflecting the watershed hydrology,such as the volume of runoff controlled by regional precipitation or snow melt from the high altitudes around the lake.Elements Sr,Zr and Ca have significant correlations,and Ca has nearly the same loading in the first and the second principle component (runoff and wind),indicating that coarse terrigenous clasts and authigenetic components both exist in the carbonates of the sediments,to which attention should be paid when geochemistry analysis is done on carbonates in the sediments.Dissolved elements S and Cl might reflect the ratio of input water to evaporationrelated to salinity.However,these two elements should be treated with caution due to the fact that they are affected by water content in the sediments.