镇江下蜀土剖面的化学风化强度与元素迁移特征
收稿日期: 2007-05-12
修回日期: 2007-08-12
网络出版日期: 2007-11-25
基金资助
国家自然科学基金(40401006); 黄土与第四纪地质国家重点实验室开放基金(SKLLQG0304); 南京大学测试 基金项目资助
Chemical Weathering Intensity and Element Migration Features of the Xiashu Loess Profile in Zhenjiang
Received date: 2007-05-12
Revised date: 2007-08-12
Online published: 2007-11-25
Supported by
National Natural Science Foundation of China, No.40401006; Open Foundation of State Key Laboratory of Loess and Quaternary Geology, No.SKLLQG0304; Experimental Foundation of Nanjing University
对镇江下蜀土剖面的化学风化强度及元素迁移特征进行了研究, 结合与黄土高原第四纪黄土、古土壤、晚第三纪红粘土以及安徽宣城风成红土等典型风成堆积剖面的对比分析, 得出如下结论: (1) 镇江下蜀土剖面经历了中等强度的化学风化, 明显强于洛川黄土以及古土壤, 显著弱于宣城风成红土, 而与西峰晚第三纪红粘土非常接近。下蜀土的化学风化过程及 其与其他风成堆积剖面风化强度的差异主要受气候条件的控制, 气候条件通过年平均温度和年降水量对化学风化的地球化学环境起重要的影响, 其中降水因素在化学风化过程中可能起着更为重要的制约作用。(2) 镇江下蜀土剖面风化过程中, 绝大部分常量元素的地球化学行为 表现为迁移淋失, 仅Fe 和Ti 轻微富集, 元素的活动性由强至弱依次为: P > Na > Ca > Mg > K > Fe2+ > Si > Mn > Al > Ti > Fe3+； 常量元素的迁移特征揭示下蜀土的化学风化已经完成初级阶段的去Ca、Na 过程, 并初步进入到去K 风化的中级阶段； 微量元素除Sr、Ga 迁移淋 失外, Th、Ba、Cu、Zn、Co、Ni、Cr、V 等均表现出富集特征, 这可能与下蜀土风化成壤过 程中的生物地球化学过程以及粘粒、有机质对微量元素的吸附作用有关。(3) 元素迁移在剖面 中的变化特征揭示, 在0.24 Ma 之前的中更新世早、中期, 该区气候较为暖湿, 兼有干湿交替的特征； 中更新世晚期气候偏干凉, 风化淋溶最弱； 至晚更新世早期则又出现一段明显暖湿的成壤时期, 形成下蜀土剖面中的S1 古土壤层。总之, 中更新世以来本区气候整体上向干凉的方向发展。
李徐生, 韩志勇, 杨守业, 陈英勇, 王永波, 杨达源 . 镇江下蜀土剖面的化学风化强度与元素迁移特征[J]. 地理学报, 2007 , 62(11) : 1174 -1184 . DOI: 10.11821/xb200711006
The chemical weathering intensity and element migration features of the Xiashu loess profile in Zhenjiang are studied in this paper. Based on the comparison with other aeolian-dust deposits, i.e. Quaternary loess-palesol and late-tertiary red-clay profiles in the Loess Plateau, and aeolian dust red earth in Xuancheng of Anhui province, we draw the following conclusions: (1) The Xiashu loess profile underwent moderate chemical weathering, which was stronger than that of the loess and palesol in Luochuan, much weaker than that of the aeolian dust red earth in Xuancheng, and similar to that of late-tertiary red-clay in Xifeng. The chemical weathering differences among the studied aeolian-dust deposits were mainly induced by the distinction of the climate condition, which imposed important influence on the geochemical environment through the mean annual temperature and annual precipitation. It seems that the annual precipitation has more important influence on the chemical weathering process. (2) The major elements such as Si, K, Na, Ca, Mg, Mn and P were migrated and leached, while the elements Fe and Ti were slightly enriched during the chemical weathering process. According to the migration ability, the major elements are ranked in the following order: P > Na > Ca > Mg > K > Fe2+ > Si > Mn > Al > Ti > Fe3+. The migration features of the major elements reveal that the Xiashu loess finished the primary process of chemical weathering characterized by leaching of Ca and Na, and almost reached the secondary process characterized by leaching of K. Except the elements Sr and Ga, other trace elements such as Th, Ba, Cu, Zn, Co, Ni, Cr and V were enriched during the chemical weathering process. And this enrichment might be caused by both the biogeochemical process and the adsorption of trace elements by clay mineral and organic materials during the chemical weathering. (3) The difference of element migration down the Xiashu loess profile reveals that the climate was warm and wet at the early-middle stage of the Middle Pleistocene (before 0.24 Ma), however, bearing the feature of an alternate dry and wet fluctuation. At the end of the Middle Pleistocene, it became dry and cool, which resulted in the weakest weathering and element migration. At the early stage of the Late Pleistocene, the paleoclimate became warm and wet again, which led to rather strong pedogenesis and the formation of the paleosol S1 in the Xiashu loess profile. As a whole, the paleoclimate generally became drier and cooler in this region from the beginning of the Middle Pleistocene.
Key words： Xiashu Loess; chemical weathering; element migration; Zhenjiang
[1] Chen Jun, Ji Junfeng, Chou Gang et al. Geochemistry of the chemical weathering intensity of the loess profile in Luochuan, Shaanxi Province. Science in China (Series D), 1997, 27(6): 531-536.
[陈骏, 季峻峰, 仇纲等. 陕西洛川黄 土化学风化程度的地球化学研究. 中国科学(D 辑), 1997, 27(6): 531-536.]
[2] Diao Guiyi, Wen Qizhong. The migration series of major elements during loess pedogenesis. Geology-Geochemistry, 1999, 27(1): 21-26.
[刁桂仪, 文启忠. 黄土风化成土过程中主要元素迁移序列. 地质地球化学, 1999, 27(1): 21-26.]
[3] Yang Shouye, Li Congxian, Li Xusheng et al. Geochemical records of chemical weathering of the Xiashu Loess in the lower reachers of the Changjiang River. Geochimica, 2001, 30(4): 402-406.
[杨守业, 李从先, 李徐生等. 长江下游下 蜀黄土化学风化的地球化学研究. 地球化学, 2001, 30(4): 402-406.]
[4] Li Xusheng, Yang Dayuan. Magnetic susceptibility features and environmental records of the Xiashu Loess in Zhenjiang, Jiangsu Province. Journal of Desert Research, 2002, 22(1): 27-32.
[李徐生, 杨达源. 镇江下蜀黄土- 古土壤序列磁化率 特征与环境记录. 中国沙漠, 2002, 22(1): 27-32.]
[5] Li Xusheng, Yang Dayuan, Lu Huayu. Grain-size features and genesis of the Xiashu Loess in Zhenjiang. Marine Geology & Quaternary Geology, 2001, 21(1): 25-32.
[李徐生, 杨达源, 鹿化煜. 镇江下蜀黄土的粒度特征及其成因初探. 海洋 地质与第四纪地质, 2001, 21(1): 25-32.]
[6] Li Xusheng, Han Zhiyong, Yang Dayuan et al. REE geochemistry of Xiashu Loess in Zhenjiang, Jiangsu Province. Acta Pedologica Sinica, 2006, 43(1): 1-7.
[李徐生, 韩志勇, 杨达源等. 镇江下蜀黄土的REE 地球化学特征研究. 土壤学 报, 2006, 43(1): 1-7.]
[7] Chen Jun, An Zhisheng, Liu Lianwen et al. Variations in chemical compositions of the eolian dust in Chinese Loess Plateau over the past 2.5Ma and chemical weathering in the Asian inland. Science in China (Series D), 2001, 2001, 31 (2): 136-145.
[陈骏, 安芷生, 刘连文等. 最近2.5Ma 以来黄土高原风尘化学组成的变化与亚洲内陆的化学风化. 中 国科学(D 辑), 2001, 31(2): 136-145.]
[8] Chen Yang, Chen Jun, Liu Lianwen. Chemical composition and characterization of chemical weathering of late Tertiary red clay in Xifeng, Gansu Province. Journal of Geomechanics, 2001, 7(2): 167-175.
[陈旸, 陈骏, 刘连文. 甘肃西峰晚 第三纪红粘土的化学组成及化学风化特征. 地质力学学报, 2001, 7(2): 167-175.]
[9] Li Xusheng, Yang Dayuan, Lu Huayu. Oxide-geochemistry features and paleoclimatic records of the aeolian-dust depositional sequence in southern Anhui Province. Marine Geology & Quaternary Geology, 1999, 19(4): 75-82.
[ 李徐 生, 杨达源, 鹿化煜. 皖南风尘堆积序列氧化物地球化学特征与古气候记录. 海洋地质与第四纪地质, 1999, 19(4): 75-82.]
[10] Taylor S R, McLennan S M. The Continental Crust: Its Composition and Evolution. London: Blackwell, 1985, 277.
[11] Feng Lianjun, Chu Xuelei, Zhang Qirui et al. CIA and its applications in the Neoproterozoic clastic rocks. Earth Science Frontiers, 2003, 10(4): 539-544.
[冯连君, 储雪蕾, 张启锐等. 化学蚀变指数(CIA) 及其在新元古代碎屑岩 中的应用. 地学前缘, 2003, 10(4): 539-544.]
[12] Nesbitt H W, Young G M. Early Proterozoic climates and plate motions inferred from major element chemistry of lutites. Nature, 1982, 299: 715-717.
[13] McLennan S M. Weathering and global denudation. Journal of Geology, 1993, 101: 295-303.
[14] Nesbitt H W, Markovics G, Price R C. Chemical processes affecting alkalis and alkaline earths during continental weathering. Geochem Cosmochim Acta, 1980, 44(11): 1659-1666.
[15] Pang Jiangli, Huang Chunchang, Zhang Zhanping. Pb, Ca, Zn, Cd, Mn elements and climatic change in the loess-paleosol profile at Qishan, Shaanxi Province. Journal of Desert Research, 2001, 21(2): 151-156.
[ 庞奖励, 黄春 长, 张占平. 陕西五里铺黄土微量元素组成与全新世气候不稳定性研究. 中国沙漠, 2001, 21(2): 151-156.]
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