基于地质建造的土壤-岩石地球化学特征研究——以吉林延吉地区为例

    Soil-rock geochemistry of Yanji area, Jilin Province: Based on geological formation

    • 摘要: 为探讨延吉地区不同地质建造与生态环境的作用关系,支撑区域生态管理,对延吉市低山丘陵区6个地质建造中土壤-母质-岩石常量元素和微量元素的分布和迁移规律进行分析研究.结果表明:各类元素在6个地质建造单元土壤-母质-基岩中地球化学特征具有一致性,证明该区土壤主要是由岩石建造就近风化而成;土壤、母质、基岩化学蚀变指数(CIA)平均值为61.62,说明该区不同地质建造单元剖面总体处于寒冷干燥气候条件下低等的化学风化程度,并且CIA值总体呈现出土壤层 > 母质层 > 基岩层的规律.元素相对迁移率研究显示该区除新近纪基性火山岩建造外,其他地质建造单元化学风化基本完成了早期的去Ca、Na风化过程,并初步进入到了中期的去K风化阶段,不同地质建造单元中微量元素除Nb表现为不同程度的亏损外,Y、Zr、Ce、La、Sr、Ba、Rb、U均有随风化富集或亏损的特征,并且Y、Zr、Ce、La,以及Sr、Ba、Rb分别具有相似的元素地球化学迁移规律.

       

      Abstract: To explore the relationship between different geological formations and ecological environment in Yanji area for regional ecological management, this study analyzes the distribution and migration patterns of major and trace elements in the soil-parent material-bedrock of six geological formations in the low hilly area of Yanji City. The results show that the geochemical characteristics of various elements exhibit consistency within the soil-parent material-bedrock profiles of the six geological formations, demonstrating that the soil in the area was primarily originated from the in-situ weathering of local rock formations. The average chemical index of alteration(CIA)value for soil, parent material and bedrock is 61.62, indicating that the profiles across different geological formation units generally experienced lowintensity chemical weathering under cold and arid climatic conditions, with the CIA values consistently following the law of soil layer > parent material layer > bedrock layer. The study on the relative migration rates of elements reveals that, except for the Neogene basic volcanic formation, the chemical weathering in other geological formation units has largely completed the early-stage depletion of Ca and Na, and has preliminarily entered the mid-stage depletion of K.Among the trace elements in different geological formations, Nb shows varying degrees of depletion, while Y, Zr, Ce, La, Sr, Ba, Rb, and U exhibit either enrichment or depletion patterns influenced by weathering. Besides, Y, Zr, Ce, and La, as well as Sr, Ba, and Rb, respectively, display similar geochemical migration behaviors.

       

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