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
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
LI Xusheng, HAN Zhiyong, YANG Shouye,CHEN Yingyong, WANG Yongbo, YANG Dayuan . Chemical Weathering Intensity and Element Migration Features of the Xiashu Loess Profile in Zhenjiang[J]. Acta Geographica Sinica, 2007 , 62(11) : 1174 -1184 . DOI: 10.11821/xb200711006
[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.]
/
| 〈 |
|
〉 |