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通过对青藏高原西部昂拉仁错湖古湖岸阶地钙华常量地球化学元素的分析,探讨了钙华沉积的常量元素特征及其古环境意义。结果显示:钙华中CaO含量达34.75%~58.48%,是其主要组分;此外还含有少量的MgO,K_2O和Na_2O等,其含量低于3%,是湖泊自生作用形成的矿物。与湖泊古水位对比显示,元素Mg的含量及Mg/Ca比值等对湖泊水位的响应没有明显规律性;在古湖面高度约4777±5m之上,K_2O和Na_2O的含量低并且稳定,在古湖面4777±5m之下,K_2O和Na_2O的含量随湖泊水位下降逐渐增加。结合现代湖泊钙华的沉积特征,结果显示K_2O和Na_2O的含量随湖泊盐度增加而增加,表明钙华中K_2O和Na_2O含量与湖泊水位可能呈反相关关系,是潜在的重建湖泊水位或盐度的代用指标。同时发现,在湖泊相对淡化阶段,湖水中的元素K和Na处于富集阶段,钙华中K_2O和Na_2O含量低且稳定;而当湖泊进入咸水阶段,湖水中的K~+和Na~+离子接近饱和,钙华中的元素K和Na逐渐富集,因此钙华中K_2O和Na_2O含量增加是湖泊进入咸水阶段的重要特征。基于这些事实,推断当该湖泊水位降至4777±5m左右时,湖水的性质开始向钠-氯型转化,是昂拉仁错湖泊演化过程中的一个重要转折点。
Based on the analysis of the geochemical elements of travertine in terraces of the ancient lakeshore of Lake Unraren in the west Qinghai-Tibet Plateau, the characteristics of the elements of travertine deposits and their paleoenvironmental significance are discussed. The results showed that the content of CaO in travertine was 34.75% -58.48%, which was the main component. In addition, a small amount of MgO, K2O and Na2O were contained in the travertine, whose content was less than 3%. Compared with the paleo-water level of the lake, the content of Mg and Ca / Mg ratio did not have obvious regularity to the lake water level. The K2O and Na2O contents were low and stable above the ancient lake about 4777 ± 5m, Under 4777 ± 5m, the content of K2O and Na2O gradually increased with the decrease of lake water level. Based on the sedimentary characteristics of modern lake travertine, the results show that the contents of K 2 O and Na 2 O increase with the increase of lake salinity, indicating that K 2 O and Na 2 O contents in travertine may be inversely related to the lake water level, which is potential for reconstructing lake water level or salinity Alternative indicators. At the same time, it was found that K and Na in lake water are in the enrichment stage and K 2 O and Na 2 O content in travertine lake are low and stable in lakes relatively desalting stage. When lakes enter saltwater stage, K + and Na + ions in lake water Close to saturation, elements K and Na in travertine are gradually enriched. Therefore, the increase of K 2 O and Na 2 O content in travertine is an important feature of lakes entering the saltwater phase. Based on these facts, it is inferred that when the water level of the lake drops to about 4777 ± 5m, the nature of the lake starts to transform into sodium-chlorine type, which is an important turning point in the lake evolution of the Anurarin Lake.