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本文对汉江上游黄土的常量元素含量及相关地球化学参数CIA、Na/K、淋溶系数、退碱系数、残积系数等进行了系统分析。结果显示:1汉江黄土的主要化学成分为Si O2、Al2O3和Fe2O3,三者含量总和达767.3 g/kg;常量元素含量大小排序为Si O2>Al2O3>Fe2O3>K2O>Mg O>Na2O>Ca O。风化成壤过程中Na、Ca、Mg、Si发生不同程度的迁移淋溶,而Fe、Al、K相对富集。2其风化成壤强度呈现从马兰黄土L1→过渡性黄土Lt→古土壤S0逐渐升高、全新世黄土L0又降低的规律,记录了该区域气候经历了末次冰期(55.0-15.0 ka BP)冷干、早全新世(15.0-8.5 ka BP)增温增湿、中全新世(8.5-3.1 ka BP)达到最暖湿,晚全新世(3.1-0.0 ka BP)降温变干的演变过程。3汉江黄土与洛川、巫山、下蜀黄土的元素组合特征高度一致,不同地区常量元素(Ca O除外)含量十分接近且UCC标准化值变幅均小于0.25,这暗示了它们风化之初具有相似的风成沉积基础;但不同区域黄土的化学风化强度差异明显,大致呈现洛川黄土<汉江黄土<巫山黄土<下蜀黄土的趋势,与中国现代季风气候的空间变化规律相吻合,即不同地区黄土风化程度差异主要是东亚季风变化影响的结果。
In this paper, the contents of major elements and the related geochemical parameters CIA, Na / K, leaching coefficient, dealkalization coefficient and residual coefficient of loess in the upper reaches of the Hanjiang River were systematically analyzed. The results show that: 1 The main chemical components of loess in Hanjiang River are Si O2, Al 2 O 3 and Fe 2 O 3, the total contents of these three are up to 767.3 g / kg; the order of the major elements is Si O2> Al 2 O 3> Fe 2 O 3> K 2 O> Mg O> Na 2 O> . Na, Ca, Mg, Si migrated and leached to different degrees during weathered pedogenesis, whereas Fe, Al and K were relatively enriched. 2 The weathering and pedogenetic intensity showed a gradual increase of L0 → L0 → L0 from the Loess Plateau in the Malan loess, and the decrease of L0 in the Holocene loess. It was recorded that the climate in this area experienced the last glacial (55.0-15.0 ka BP) cold In the early Holocene (15.0-8.5 ka BP), the temperature and humidity increased, the mid-Holocene (8.5-3.1 ka BP) reached the warmest and wetter, and the late Holocene (3.1-0.0 ka BP) cooled and dried. The characteristics of elemental assemblages of Hanjiang loess and Luochuan, Wushan and Xiashu loess are highly consistent. The contents of major elements (except CaO) in different areas are very close and the UCC normalized values are all less than 0.25, suggesting that they are similar in initial weathering But the chemical weathering intensity of loess in different regions is obviously different. The trend of Luochuan loess is consistent with the spatial variation of modern monsoon climate in China, that is, the loess The degree of weathering is mainly the result of the change of the monsoon in East Asia.