青海湖沉积碳酸盐矿物之间氧同位素分馏的评估及其环境意义  

Evaluation of Oxygen Stable isotope Fractionation among Different Carbonate Minerals in the Sediments of Lake Qinghai

作　　者：余俊清[1] 曾承[1] 张丽莎[1] 刘子亭[1] 

机构地区：[1]中国科学院青海盐湖研究所西安二部,西安710043

出　　处：《湖泊科学》2004年第3期223-226,共4页Journal of Lake Sciences

基　　金：中国科学院青海盐湖所创新前沿项目(CX200302);国家自然科学基金项目(49971074);中国科学院资环创新重大项目(KZCX1-Y-05)

摘　　要：青海湖沉积岩芯的矿物学和稳定同位素研究结果显示自生碳酸盐矿物以单种或多种矿物形式保存在沉积物中;不同碳酸盐样品的δ18O值的变化范围为5.47‰至-1.04‰,差值最高达6.5‰;δ18O值与总碳酸盐含量呈正相关关系,与碳酸盐矿物种类的改变则无明显关联.结果表明,造成δ18O显著变化的主导因素是湖水氧同位素组成,自然条件下生成的不同碳酸盐之间的氧同位素分馏不明显.说明δ18O是指示闭流湖泊降水蒸发水量平衡变化的敏感指标之一.Mineralogical examination and stable isotope analyses for the Lake Qinghai sediments indicate that authigenic carbonate minerals are present either in the form of one type or several types in the sediments, and that large differences in δ18O of up to 6.5‰are shown for selected sediment samples. These δ18O values are highly and positively correlated with total carbonate contents (TCC) and are not effected by shifts in carbonate mineral composition. This indicates that oxygen stable isotope fractionation among different carbonate minerals is minimum. The results suggest that marked changes in carbonate δ18O are resulted predominantly from changes in isotopic composition of the lake water. Our data support the conclusion that isotope fractionation among co existing carbonate minerals formed in natural environmental conditions are limited to 0-1‰in δ18O. The δ18O proved to be a useful environmental proxy for the study of the past changes in P-E budget of closed basin lakes.

关 键 词：青海湖 沉积岩芯 碳酸盐矿物 氧同位素分馏 环境变化 

分 类 号：P512.32[天文地球—地质学]