丰宁黄土-古土壤剖面常量元素地球化学特征

发布时间：2019-07-03 09:15

【摘要】：丰宁滦河上游的河谷地带有多处黄土堆积,由于该地区黄土分布零星、厚度较小,在以往的研究中却很少引起人们的关注,然而该地区黄土堆积是河北坝上地区环境演化和气候变化的重要地质记录.为了探讨该地区黄土的成因、物源以及化学风化强度,选取代表性的黄土-古土壤剖面77个样品进行了常量元素分析,并与已知典型风成堆积物的地球化学元素特征进行对比.结果表明:(1)丰宁剖面的主要常量元素(SiO_2、Al_2O_3和Fe_2O_3)之和以及UCC(Upper Continental Crust)标准化曲线均与典型风成堆积物具有较好的相似性,表明丰宁黄土和古土壤为风成成因;(2)丰宁黄土处于初等化学风化阶段,古土壤则进入了中等化学风化阶段.与典型风成堆积物相比,化学风化强度序列为:宣城风成红土西峰红黏土、镇江下蜀土丰宁古土壤、洛川古土壤洛川黄土丰宁黄土;(3)常量元素迁移特征表明丰宁黄土和古土壤的化学风化已完成了早期去Na、Ca阶段,并进入到了中期去K阶段;(4)丰宁黄土、古土壤的K_2O/Al_2O_3和Fe_2O_3/Al_2O_3比值与洛川黄土、洛川古土壤、镇江下蜀土、西峰红黏土较为接近,表明这些风成堆积物可能具有相似的源区.而TiO_2/Al_2O_3比值小于其他风成堆积物,指示丰宁剖面具有其他物源.
[Abstract]:There are many loess deposits in the valley of the upper reaches of Fengning Luanhe River. Because of the sporadic distribution and small thickness of loess in this area, it has rarely attracted people's attention in previous studies. However, loess accumulation in this area is an important geological record of environmental evolution and climate change in Bashang area, Hebei Province. In order to explore the genesis, provenance and chemical weathering intensity of loess in this area, 77 representative loess-paleosol profiles were selected for constant element analysis and compared with the characteristics of geochemical elements of typical aeolian deposits. The results show that: (1) the sum of the main constant elements (SiO_2,Al_2O_3 and Fe_2O_3) and the UCC (Upper Continental Crust) standardized curve of Fengning section are similar to those of typical aeolian deposits, indicating that Fengning loess and paleosol are of aeolian origin, and (2) Fengning loess is in the stage of primary chemical weathering, while the paleosol has entered the middle chemical weathering stage. Compared with the typical aeolian accumulation, the chemical weathering intensity sequence is as follows: Xuancheng aeolian red soil Xifeng peak red clay, Zhenjiang Xiashu soil Fengning paleosol, Luochuan paleosol Luochuan loess Fengning loess, (3) the migration characteristics of constant elements show that the chemical weathering of Fengning loess and paleosol has completed the early Na,Ca stage and entered the middle stage of K removal. (4) the K_2O/Al_2O_3 and Fe_2O_3/Al_2O_3 ratios of Fengning loess and paleosol are similar to those of Luochuan loess, Luochuan paleosol, Zhenjiang Xiashu soil and Xifeng red clay, indicating that these aeolian deposits may have similar source areas. The ratio of TiO_2/Al_2O_3 is smaller than that of other aeolian deposits, indicating that Fengning section has other provenances.
【作者单位】：中国地质科学院水文地质环境地质研究所;中国地质大学地球科学学院;中国地质大学地球物理与空间信息学院;
【基金】：国家自然科学基金项目(No.41602194) 中国地质科学院基本科研业务费专项(No.YWF201411)
【分类号】：P595

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