攀枝花地区昔格达组地层稀土元素地球化学特征及其古环境意义

Geochemistry Features and Palaeoenvironmental Significance of Rare Earth Elements in Xigeda Formation,Panzhihua

昔格达组是广泛分布于我国西南地区的第四纪湖相沉积地层。对攀枝花青龙山砖厂内31.5 m厚的昔格达组剖面进行了稀土元素的研究,剖析了稀土元素及其比值在该地层中的分布特征和古环境意义。研究表明,剖面从31.5～14.8 m,各稀土含量较高;而从14.8～0 m,稀土含量整体降低。这一特征表明,在该地层沉积时期,沉积环境经历了从弱还原环境(31.5～14.8 m)向还原环境(14.8～0 m)转化的过程;各元素含量在整个剖面上具有整体波动的特点,但波动较大,说明沉积过程中存在多次亚一级的环境阶段性变化;总体来说,该地层沉积环境表现为弱还原/还原环境交替,大体以暖湿还原环境为主导。

Xigeda formation is widely distributed in the southwest region of China as a quaternary lacustrine sediment.By the study of the rare earth elements of Xigeda formation in Qinglongshan brick,Panzhihua,the evolution significance of the distribution of the rare earth elements and its ratio have analyzed.The results show that,in the thickness of 0~14.8 m of the profile,the content of each rare earth elments have reduced respectively.It indicated that the depositional environment between the thickness of the profile 0~14.8 m changed from weak oxygen-free environment to oxygen-free environment,whereas it is on the contrary between 14.8~31.5 m.The content of each element in the whole profile has an overall volatility feature,but the greater fluctuation indicating that there are several times sub-level changes in the environment during the deposition process stage.In sum,the sedimentary environment of this formation performance shows a weak oxygen-free/oxygen-free environment alternatively,largely dominated by warm,wet and reducing environment.