辽南黄土覆盖的红色风化壳发育特征及区域对比

通过分析辽南七顶山黄土覆盖的红色风化壳地球化学特征，研究其发育特征并与湘桂黔滇青藏陕甘红色风化壳发育特征进行比较，为了解黄土覆盖的红色风化壳发育特征及不同地区红色风化壳发育特征的空间差异提供初步依据。化学元素实验表明，七顶山剖面红色风化壳主量元素平均值分布呈现如下趋势:SiO₂ > Al₂O₃ > Fe₂O₃ > K₂O > CaO > MgO > Na₂O，化学蚀变指数（CIA）介于83.19 ~ 86.89，盐基淋溶率（ba）介于0.26 ~ 0.35，铝饱和指数A/NK介于6.10 ~ 7.47，A/CNK介于3.93 ~ 4.99，S/A介于5.24 ~ 6.47，S/R介于4.53 ~ 5.50。结果表明:七顶山剖面红色风化壳呈正风化序列，是下伏基岩原地风化的产物，化学组成以SiO₂、Al₂O₃、Fe₂O₃为主，三者之和超过86%，处于还原环境，属于脱硅脱铁富铝阶段，发育于近似亚热带的气候条件，处于高等化学风化水平。辽南在116.13 ~ 90.48 Ma B.P.至17.70 ~ 9.44 Ma B.P.时具备红色风化壳发育的气候条件，结合残存红色风化壳和石芽的情况，可以认为其开始发育于中新世中期或更早。辽南红色风化壳第四纪以前为二阶段发育过程，即夷平—成壳、切割—红化期，第四纪至今仅有切割—红化期。湘桂黔滇青藏陕甘辽红色风化壳元素组合特征高度一致，各区域红色风化壳风化强度、风化方向接近，除辽南呈现较弱的脱硅脱铁富铝趋势外，其他区域均表现为脱硅富铝铁化趋势，这暗示了黄土覆盖下的红色风化壳处于还原环境。纬度因素和经度因素对红色风化壳脱硅富铝铁化进程影响程度接近，相较于经度因素，纬度因素对红色风化壳碱金属及碱金属盐基淋溶作用影响程度更大，总体而言，在母岩影响较小的前提下，纬度控制下的气候因素是决定红色风化壳发育的主要因素。

Development Characteristics and Regional Comparison of Loess?covered Red Weathering Crust in Southern Liaoning

By analyzing the geochemical characteristics of the loess?covered red weathering crust in the Qidingshan area of southern Liaoning， the development characteristics are studied and compared with those of red weathering crust in Hunan， Guangxi， Guizhou， Yunnan， Tibet， Shanxi， and Gansu in order to understand the development characteristics of loess?covered red weathering crust and provide a preliminary basis of the spatial difference of its development characteristics in different regions. The chemical element experiments show that the average distribution of the main elements for the red weathering crust in the Qidingshan section experiences the following trend: SiO₂ > Al₂O₃ > Fe₂O₃ > K₂O > CaO > MgO > Na₂O. CIA is between 83.19?86.89， Ba is between 0.26?0.35， A/NK is between 6.10 and 7.47， A/CNK is between 3.93 and 4.99， S/A is between 5.24 and 6.47， and S/R is between 4.53 and 5.50. The conclusion shows that the red weathering crust from the Qidingshan section has a positive weathering sequence， which is the product of weathering the underlying bedrock. The chemical composition is mainly composed of SiO₂， Al₂O₃， and Fe₂O₃. The sum of the three is more than 86%， which constitutes a reductive environment， indicating desiliconization and deironing. This stage develops in a subtropical climate with a high level of chemical weathering. The climatic conditions of the red weathering crust development are provided in Liaoning Province from 116.13 Ma to 90.48 Ma and from 17.70 Ma. to 9.44 Ma， combined with the residual red weathering crust and stone bud， and can be considered to be from the mid?Miocene or earlier. The red weathering crust of southern Liaoning was a two?stage development process before the Quaternary， namely， the flattening?shelling， cutting?reddening period. The Quaternary has only had a cutting?reddening period. The element characteristics of the red weathering crust of Hunan， Guangxi， Guizhou， Yunnan， Tibet， Shanxi， Gansu， and Liaoning are highly consistent. The weathering intensity and direction in each region are similar. Except for the weak desiliconization， deironing， and aluminum?rich trend in southern Liaoning， other regions indicate a trend of desiliconization and aluminum?rich ironification， which suggests that the loess?covered red weathering crust is in a reductive environment. The latitude and longitude factors have similar effects on the desiliconization and aluminum?rich ironation process of red weathering crust. Compared with the longitude factors， the latitude factors have a greater influence on the alkali metal and alkali metal leaching of red weathering crust. In general， under the premise of less influence from the parent rock， the climatic factors under latitude control are the main factors determining the development of red weathering crust.