摘要
本文根据察尔汗盐湖现代钾盐沉积区补给水的化学组成和沉积物岩芯中原生石盐流质包裹体的氢氧同位素组成,研究了钾盐卤水的形成和钾盐蒸发岩的沉积模式。论述了古代异常钾盐蒸发岩可能是或部分是非海相成因的。
Based on the chemical composition of inflow waters of Qarhan Salt Lake in the Qaidam Basin as well as on the hydrogen and oxygen isotopic composition of primary halite fluid inclusions collected from evaporite sediments cores, we have studied the formation of potash brines in modern salt lakes and proposed a model for potash evaporite deposition.Our study indicates that the mixture of river and spring inflows in different proportions can evolve into Na-HCO3-SO4, Cl-SO4 and Ca-Cl brines. Boundary ratio are 40 and 80 Various minerals in the potash evaporites can be obtained from the three types of brine by evaporation and crystallization. Therefore, a forming sequence of nonmarine potash evaporites is established. Generally, the Qarhan Salt Lake falls within the category with a ratio of river over spring inflow close to 40 Evaporite minerals, for example, calcite, gypsum, anhydrite, halite, carnallite, bischofite and so on can be deposited under this condition. This is just the mineral sequence of the so-called anomalous marine evaporites.Changes in δD and δ18O of inclusion water in primary halite illustrate that the ancient Qarhan Lake had undergone three quite different evolutionary periods. During the early salt-precipitating period, the δD and δ18O values were close to one another; during the intermediate period, the values were relatively low; and during the late period, salt-precipitating brine was in a temperature-rise phase. During these three periods, the waterbody environment once varied intensely. Such variations are of environmental significance for the accumulation of potash in the waterbody and the formation of potash sediments.Some mineral deposits associated with the so-called anomalous potash evaporites are of continental origin, which are similar to those in the Qarhan Salt Lake. During the late period of brine evolution, undulating climatic environment is an important precondition for the formation of potash sediments.
出处
《地球化学》
CAS
CSCD
北大核心
1991年第2期134-143,共10页
Geochimica
基金
国家自然科学基金
