网纹红土稀土元素地球化学特征的初步研究

摘要/Abstract

摘要： 稀土元素(REE)在揭示沉积环境,研究沉积物物源及成因方面具有重要的示踪意义。江西、湖南、浙江等地更新世加积型红土REE含量和分布特征的研究结果表明: ①除结核外,红土各类样品的REE总量变化于158.2～224.0 μg\5g-1之间。由大至小排序为:无网纹棕黄色土>无网纹均质红土>网纹红土。网纹层内白网纹REE含量高于红网纹。结核样品REE异常富集,是网纹红土母质的3～6倍,Ce富集为主要贡献者。②来自中亚热带地区不同红土沉积剖面的各类网纹红土样品,其稀土分布模式相似,与上地壳(UCC)稀土组成相近。比较研究发现,网纹红土母质与黄土高原黄土、镇江下蜀黄土、西峰第三纪红粘土的稀土配分模式非常一致,而与碳酸盐红土、花岗岩红土存在明显差异。这些特征暗示网纹红土母质与北方黄土红粘土间存在物源联系,网纹红土物质组成均匀,经历了高度混合,显示风成特性。③网纹红土稀土元素特征一方面继承了原始物质的特性,另一方面体现了南方湿热气候条件下,化学风化导致的再分馏特征。化学风化中,Eu未出现明显的再分馏,而Ce的再分馏显著。通常情况下,风化淋溶指数越小,Ce富集程度越高。然而,网纹化过程中Ce分馏特征显示出复杂性。

关键词: 稀土元素, 网纹红土, 第四纪红土, 中亚热带

Abstract: Rare earth elements(REE) have important tracing significance on studies about sedimentation environment, source and forming of sediments. We have studied the REE composition for plinthitic red earth and their distribution characteristics in Jiangxi, Hunan, Zhejiang provinces. The findings show that ①∑REE of all kinds of plinthitic red earth samples except for nodule samples vary in range from 158.2 to 224.0 μg\5g-1. Compared with the other samples, nodule samples are much higher in REE absorbed abundance, from 385.5 to 1 641.6 μg\5g-1, especially the Cerium element absorbed abundance. The REE abundance of un-vermiculate samples is higher than that of vermiculate samples, and the REE abundance of white vermiculate samples is higher than that of red vermiculate samples. ②Though these samples come from different places or ages, their REE distribution patterns are almost identical, which displays uniformity of plinthitic red earth in material composition. They were quite similar to the upper continent crust (UCC) in REE distribution pattern, showing “rich LREEs and Europium-depletion” characteristics. By further comparison with the loess in Loess Plateau, Xiashu loess in Zhenjiang, red clay in Xifeng, carbonite red clay in Guizhou and granite red clay in Guangdong, we find that the plinthitc red earth in REE distribution pattern and characteristic parameters are more closed to loess-red clay in northern China, which implies their material origin are identical. So, the materials of plinthitic red earth might get highly mixed as aeolian dust during the process of transportation. ③The REE characteristics of plinthitic red earth are inherited from its source materials, and also lead to REE re-fractionation characteristics because of stronger chemical weathering and soil-forming process. On the whole, the fractionation between LREE and HREE for plinthitic red earth is significantly apparent, Europium (Eu) fractionation is not any apparent, Cerium (Ce) fractionation is remarkable during weathering. Normally, Ce absorbed abundance is negatively related to ba (weathering-eluviating index) value, meanwhile, Ce-depletion become more complicated during vermiculate process.

Key words: rare earth element (REE), plinthitic red earth, Quaternary red earth, mid-subtropics

中图分类号:

P595

朱丽东;周尚哲;叶玮;李凤全;王天阳. 网纹红土稀土元素地球化学特征的初步研究[J]. 中国沙漠, 2007, 27(2): 194-200.

ZHU Li-dong;ZHOU Shang-zhe;YE Wei;LI Feng-quan;WANG Tian-yang. Preliminary Study on Geochemical Behavior of Rare Earth Element of Plinthitic Red Earth in South China[J]. JOURNAL OF DESERT RESEARCH, 2007, 27(2): 194-200.

参考文献

[1]刘东生.黄土与环境[M].北京:科学出版社,1985:238-264.
[2]李明启,靳鹤龄,董光荣,等.萨拉乌苏河流域微量元素揭示的气候变化[J].中国沙漠,2006,26(2):172-179
[3]李云卓,李保生,高全洲,等.巴丹吉林查格勒布剖面记录的150 ka BP以来的常量化学元素波动[J].中国沙漠,2005,25(1):8-14.
[4]杨守业,李从先.长江与黄河沉积物REE地球化学及示踪作用[J].地球化学,1999,28(4):374-380.
[5]黄成敏,龚子同.土壤发育过程中稀土元素的地球化学指示意义[J].中国稀土学报,2000,18(2):150-155.
[6]曾从盛.闽东南沿海老红砂的地球化学特征[J].中国沙漠,2000,20(3):248-251.
[7]席承藩.关于中国红色风化壳的几个问题[J].中国第四纪研究,1965,4(2):42-54.
[8]朱显谟.中国南方的红土和红色风化壳[J].第四纪研究,1993(1):75-84.
[9]章明奎.浙江省第四纪古红土[J].热带亚热带土壤科学,1995,4(3):141-146.
[10]杨达源.中国东部的第四纪风尘堆积与季风变迁[J].第四纪研究,1991(4):20-24.
[11]熊尚发,丁仲礼,刘东生,等.赣北红土与北京邻区黄土及沙漠砂的粒度特征对比[J].科学通报,1999,44(11):1216-1219.
[12]李徐生,杨达源,鹿化煜,等.皖南第四纪风尘堆积序列粒度特征及其意义[J].海洋地质与第四纪地质,1997,17(4):73-81.
[13]胡雪峰,龚子同.江西九江泰和第四纪红土成因的比较研究[J].土壤学报,2001,38(1):1-9.
[14]胡雪峰,朱煜,沈铭能,等.南方网纹红土多元成因的粒度证据[J].科学通报,2005,50(9):918-925.
[15]李吉均,张林源,邓养鑫, 等.庐山第四纪环境演变和地貌发育问题[J].中国科学:B辑,1983(8):734-743.
[16]丁梦林,方仲景,计凤桔,等.对长江下游雨花台砾石层及网纹红土地层划分及时代的新认识[C]//第四纪冰川与第四纪地质论文集(第三集).北京:科学出版社,1987:139-143.
[17]王立军,王玉琦,章申,等.中国不同类型土壤中稀土元素的形态分布特征[J].中国稀土学报,1997,15(1):64-70.
[18]Liu F,Colombo C,Adamo P,et al.Trace elements in manganese iron nodules from a Chinese Alfisol[J].Soil Science Society of America Journal,2002,66: 661-670.
[19]Singh B,Gilkes R J.Properties and distribution of iron oxides and their association with minor elements in the soils of southern-Australia[J].Journal of Soil Science,1992,43:77-98.
[20]吴明清,文忠启,潘景瑜,等.黄河中游地区马兰黄土的稀土元素[J].科学通报,1991,36(5):366-369.
[21]李徐生,韩志勇,杨达源,等.镇江下蜀黄土的稀土元素地球化学特征研究[J].土壤学报,2006,43(1):1-7.
[22]彭淑贞,郭正堂.西峰地区晚第三纪红土稀土元素的初步研究[J].海洋地质与第四纪地质,2000,20(2):39-43.
[23]王世杰.贵州平坝县白云岩风化壳中稀土元素分布特征之初步研究[J].地质科学,2001,36 (4):474-480.
[24]刘秀敏.贵州碳酸盐岩风化壳形成地球化学过程、对比及年代学研究[D].贵阳:中国科学院地球化学研究所,2003.55-58.
[25]刑光熹,朱建国著.土壤微量元素与稀土元素化学[M].北京:科学出版社,2003:73-81.
[26]朱丽东,叶玮,周尚哲,等.中亚热带第四纪红粘土的粒度特征[J].地理科学,2006,26(5):586-591.
[27]叶玮著.新疆西风区黄土沉积特征与古气候[M].北京:海洋出版社,2001:85-91.