柴达木盆地西部尕斯库勒盐湖周缘岩系和湖内沉积物含铀性模拟

 以柴达木盆地西部尕斯库勒盐湖周缘岩系和湖内沉积物为研究对象,通过淋滤实验和悬浮平衡模拟实验,探讨该盐湖不同物源的含铀性.分析表明,尕斯库勒盐湖周缘3 种岩系(老地层、上新世含盐岩系、第四纪沉积物)淋滤液水化学特征类似,且从淋滤液水化学特征可知该盐湖水化学具有明显的再溶盐特征;3 种岩系淋滤作用强烈,盐湖第四纪沉积物中的铀最容易被淋出,上新世含盐岩系中的铀次之,蚀源区岩石中的铀难淋出;悬浮平衡实验表明,悬浮液中铀含量随平衡时间增长呈现先迅速降低而后缓慢升高的变化趋势,而沉积颗粒物中铀含量变化趋势与悬浮液中铀含量刚好相反,说明铀在悬浮液和沉积颗粒物之间确实发生了交换,且交换速率较快;在平衡实验初期,悬浮液中铀含量快速降低的现象可能是悬浮液中的铀被固相吸附所致;不同时期铀的来源分析表明,在新近纪和第四纪早期,尕斯库勒盐湖内卤水和沉积物中的铀主要来自周边岩石的风化淋滤作用,铀补给量相对较少,而到了第四纪中、晚期,铀主要来自上新世含盐岩系风化淋滤和深部水补给,再加上沉积物和周边岩石化学风化,铀补给量相对前一时期大得多.

Simulation Experiments on the Uraniferous Possibility of Peripheral Rock Series and Sediment from Gasikule Salt Lake,Western Qaidam Basin

In order to explore the uraniferous possibility in different parts of China, the leaching experiments of peripheral rock series and the equilibration experiment of sediment from Gasikule Salt Lake located in the western margin of Qaidam Basin are conducted in this paper. It is shown that the leachate has similar hydrochemical characteristics of three types of rock series (old strata, Pliocene salt-bearing strata and Quaternay sediment) around Gasikule Salt Lake. The hydrochemistry of Gasikule Salt Lake basin is deeply influenced by peripheral rock series and characterized by re-dissolved salt obviously. Three types of rock series suffer severely from eluviations, and the leaching trend is in the order of Quaternay sediment > Pliocene salt- bearing strata > old strata. In the equilibration experiment, the uranium concentration in the suspension decreases first and then slowly increases against the balance time. However, the uranium concentration in the sediments sees a reverse trend, which illustrates that the uranium has a rapid exchange between the suspension and the sediment. The uranium in the suspension absorbed by the sediment may be accounted for the decrease of the uranium concentration in the suspension at the first stage of the equilibration experiment. During Neogene and early Quarternary, the uranium in Gasikule Salt Lake's brine and sediment mainly comes from the chemical weathering in the peripheral old strata. However, the Pliocene salt-bearing strata and the deep water contain the majority of uranium sources during late Quaternary, coupled with sediment and old strata weathering, this period enjoys larger uranium supplementary amount than that in the periods of Neogene and early Quarternary.