白水黄土-红粘土化学风化强度的剖面特征与粒度效应

被引：43

作者：

熊尚发

朱园健

周茹

卢海建

丁仲礼

机构：

[1] 中国科学院地质与地球物理研究所新生代地质与环境重点实验室

来源：

第四纪研究 | 2008年 / 05期

关键词：

黄土-红粘土; 化学风化; CIA; 粒度效应;

D O I：

暂无

中图分类号：

P595 [元素地球化学];

学科分类号：

摘要：

白水剖面黄土-红粘土全样化学分析表明,以CIA指数为代表的化学风化强度从剖面下部往上逐步变弱,波动增大,总体趋势与深海氧同位素代表的全球冰量变化可以很好对比。分粒级组分化学分析则显示,黄土-红粘土主要元素迁移及化学风化强度与粒度强烈相关,CIA指数表征的化学风化强度变化在相当程度上受到粒度变化的控制。总体上,黄土-红粘土各粒级颗粒的风化程度都不高,而且沉积之后的成土风化作用对其主要元素含量的影响有限,黄土-红粘土化学成分的长期变化趋势主要受到物源的新加入和混合过程的影响。从剖面变化看,粗粒级部分(5～20μm和20～63μm)的风化指数的变化特征与细粒级部分(<5μm)不完全相同,表明不同粒级组分接受化学风化以及在物源区停留的历史不尽相同。1Ma以来,各粒级CIA指数都整体降低,显示物源区新鲜、弱风化碎屑影响到各粒级颗粒的混合过程。进一步对细粒级部分(<5μm)化学成分演化进行的分析显示,其元素含量呈现不同组分递次变化的"序列模式",从红粘土下部(约4.5Ma)到黄土上部(约0.6Ma),K2O/Al2O3,Na2O/Al2O3,CaO/Al2O3和MgO/Al2O3比率的变化依次出现转折,这很可能与晚新生代黄土-红粘土物源区构造抬升、冰川剥蚀能力不断加大,使得新鲜基岩不断被剥蚀、去顶,由此造成主要造岩矿物顺序剥蚀、接受风化,成为粉尘新物源有关。

引用

页码：812 / 821

页数：10

共 21 条

[1] Nd and Sr isotopic characteristics of Chinese deserts: Implications for the provenances of Asian dust [J].

Chen, Jun ;

Li, Gaojun ;

Yang, Jiedong ;

Rao, Wenbo ;

Lu, Huayu ;

Balsam, William ;

Sun, Youbin ;

Ji, Junfeng .

GEOCHIMICA ET COSMOCHIMICA ACTA, 2007, 71 (15) :3904-3914

[2]

Compositions of heavy minerals in Northeastern China sandlands and provenance analysis.[J].Jing Xie;ZhongLi Ding.Science in China Series D: Earth Sciences.2007, 11

[3]

Clay mineralogy of a red clay–loess sequence from Lingtai; the Chinese Loess Plateau.[J]..Global and Planetary Change.2006, 3

[4] Nd and Sr isotopic variations in Chinese eolian deposits during the past 8 Ma: Implications for provenance change [J].

Sun, JM .

EARTH AND PLANETARY SCIENCE LETTERS, 2005, 240 (02) :454-466

[5]

Provenance of loess material and formation of loess deposits on the Chinese Loess Plateau.[J].Jimin Sun.Earth and Planetary Science Letters.2002, 3

[6]

Iron geochemistry of loess and red clay deposits in the Chinese Loess Plateau and implications for long-term Asian monsoon evolution in the last 7.0 Ma.[J].Z.L. Ding;S.L. Yang;J.M. Sun;T.S. Liu.Earth and Planetary Science Letters.2001, 1

[7] Variation of Rb Sr ratios in the loess-paleosol sequences of central China during the last 130,000 years and their implications for monsoon paleoclimatology [J].

Chen, J ;

An, ZS ;

Head, J .

QUATERNARY RESEARCH, 1999, 51 (03) :215-219

[8]

Pedostratigraphy and paleomagnetism of a ～7.0 Ma eolian loess–red clay sequence at Lingtai; Loess Plateau; north-central China and the implications for paleomonsoon evolution.[J].Z.L Ding;S.F Xiong;J.M Sun;S.L Yang;Z.Y Gu;T.S Liu.Palaeogeography; Palaeoclimatology; Palaeoecology.1999, 1

[9]

Geochemical characterization of the Luochuan loess-paleosol sequence; China; and paleoclimatic implications.[J].Sylvain Gallet;Bor-ming Jahn;Masayuki Torii.Chemical Geology.1996, 1

[10]

An Index of Weathering for Silicate Rocks.[J].Andrew Parker.Geological Magazine.1970, 6

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