帮助 关于我们

返回检索结果

碳酸盐岩风化成土过程中REE超常富集及Ce强烈亏损的地球化学机理
Formation mechanisms of the superhigh concentration of REE and the strong negative Ce anomalies in the carbonate rock weathering profiles

查看参考文献24篇

文摘 碳酸盐岩的REE含量极低，但最近在贵州一些碳酸盐岩风化壳土层底部首次发现了REE的超常富集层，REE总量最高可达近31 000 μg/g；Ce强烈亏损，δCe值最低达0.007。这种低背景、高富集、强化异的REE富集现象在贵州碳酸盐岩风化壳中具有一定的普遍性。选取发育在下三叠统花溪灰岩和平坝白云岩之上的两个较具代表性的碳酸盐岩风化壳进行研究，结果表明，这种富集现象与碳酸盐岩风化成土的两阶段性密切相关。（1）在残积土形成阶段（风化早期），碳酸盐的快速溶解导致风化前缘形成一个垂直方向相对狭窄、突变的碱性障（pH值为8左右）。此障既能有效地将碳酸盐岩分解释放的REE以及下渗水携带的REE分解沉淀和吸附干粘土矿物上的方式富集，也容易使Ce~(3+)氧化成Ce~(4+)，并与HCO_3~-形成稳定的可溶性络合物随下渗雨水流走，从而使Ce进一步亏损。（2）残积土演化阶段，轻、重稀土发生明显分异，Ce~(3+)氧化成Ce~(4+)并发生水解沉淀，致使下渗水富重稀土而贫Ce，最终使REE在剖面上显示出一般风化壳共有的分异特征。另外，根据对碳酸盐岩中的酸不溶物、可溶性稀土的提取以及质量平衡计算，碳酸盐岩能够提供足够的REE物源；以可溶态为主的赋存状态有利于REE的淋滤（活化）。
其他语种文摘 As well known, the REE concentration is very low in carbonate rocks. However, superhigh concentration beds of REE, where the REE concentration can be up to about 31 000 μg/g, are found at the weathering front of carbonate rock weathering profiles in Guizhou, China. The strong negative Ce anomalies are also found in those REE enrichment beds, whose δCe can be low to 0.007. The phenomena of low background, strong enrichment and strong fractionation of REE have some certain universality in the carbonate rock weathering profiles in Guizhou. According to the results of mass balance calculation, it is considered that carbonate rocks can supply enough REE sources. The soluble existing states of REE in the parent rocks and enrichment beds, which are found by chemical leaching experiments, are in favor of activation and transportation. A sudden change and narrow alkali barrier, which is considered that it is the result of rapid solution of carbonate minerals, is also found according to the variation of the pH values of samples along the weathering profiles. The alkali barrier may be the most important factor that causes the REE enrichment. During the early stage of carbonate rocks weathering, the alkali barrier can preserve the REE effectively, which is released by weathering. And the barrier can also cause the complexes and/or ions of REE that were carried from the upper part of the profile to weathering front in infiltration water to precipitate and adsorb on clay. The strong negative anomalies of Ce in the studied profiles suggest that significant fractionation has been occurred between cerium and other rare earth elements during weathering processes. The soluble Ce~(3+) is oxidized to Ce~(4+) and precipitates from solution as very insoluble CeO_2. Consequently, the solution shows a negative Ce-anomaly. However, there is not a weathering profile or a groundwater sample in weathering profile having such strong negative Ce-anomaly as our studied profiles. And this imply that the fractionation between cerium and other rare earth elements by oxidization from Ce~(3+) to Ce~(4+) and precipitation from solution can not explain the formation of the strong negative Ce-anomaly in the studied profiles entirely. In alkali solution, Ce~(3+) can be oxidized to Ce~(4+) easily, and it has great mobilization (compared with other light REE) results from preferential formation of complexes with carbonate ligands, which are released by dissolution of carbonate minerals at weathering front. Therefore, the fractionation between cerium and other REE is not only occurred in the upper part of the profile during the later stage of weathering, but also occurred at weathering front during the early stage of weathering.
来源 地球化学 ,2002,31(2):119-128 【核心库】
关键词 碳酸盐岩 ; 风化前缘 ; REE超常富集 ; Ce强烈亏损 ; 碱性障 ; 形成机理 ; 贵州省
地址

中科院贵阳地球化学所, 环境地球化学国家重点实验室, 贵州, 贵阳, 550002

语种 中文
文献类型 研究性论文
ISSN 0379-1726
学科 地质学
基金 国家自然科学基金 ;  国家攀登计划项目
文献收藏号 CSCD:966123

参考文献 共 24 共2页

1.  王中刚. 稀土元素地球化学,1990:1-495 CSCD被引 4 次    
2.  Nesbitt H W. Mobility and fractionation of rare earth elements during weathering of a granodiorite. Nature,1979,279:206-210 CSCD被引 173 次    
3.  Duddy I R. Redistribution and fractionation of rare earth and other elements in a weathering profile. Chem Geol,1980,30:363-381 CSCD被引 31 次    
4.  杨学明. 江西大吉山花岗岩风化壳稀土矿床稀土元素地球化学. 稀土,1999,20(1):1-5 CSCD被引 15 次    
5.  宋云华. 某些岩石风化壳中稀土元素的初步探讨. 科学通报,1987,32(9):695-698 CSCD被引 33 次    
6.  Braun J J. Cerium anomalies in lateriatic profiles. Geochim Cosmochim Acta,1990,54:781-789 CSCD被引 65 次    
7.  Prudencio M I. REE mobilization, fractionation and precipitation during weathering of basalts. Chem Geol,1993,107:251-254 CSCD被引 10 次    
8.  Braun J J. Solid/liquid REE fraction in the lateritic system of Goyoum, East Cameroon: The implication for the present dynamics of the soil covers of the humid tropical regions. Geochim Cosmochim Acta,1998,62(2):273-299 CSCD被引 27 次    
9.  Lottermoser B G. Rare-earth element mineralisation within the Mt. Weld carbonatite laterite, Western Australia. Lithos,1990,24:151-167 CSCD被引 8 次    
10.  Braun J J. Mobilization and redistribution of REEs and thorium in a syenitic lateritic profile: A mass balance study. Geochim Cosmochim Acta,1993,57:4419-4434 CSCD被引 48 次    
11.  Price R C. The effects of weathering on rare-earth element. Y and Ba abundances in Tertiary basalts from southeastern Australia. Chem Geol,1991,93:245-265 CSCD被引 23 次    
12.  雷国良. 贵州岩溶沉积物稀土元素地球化学研究. 矿物学报,1994,14(3):298-308 CSCD被引 16 次    
13.  高长林. 陕西南岭碳酸盐岩的稀土元素特征及其古海洋学意义. 地球化学,1992,21(4):383-390 CSCD被引 19 次    
14.  王世杰. 碳酸盐岩风化成土作用的初步研究. 中国科学（D）,1999,29(5):441-449 CSCD被引 212 次    
15.  陈峻. 陕西洛川黄土沉积物中稀土元素及其他微量元素的化学淋滤研究. 地质学报,1996,70(1):61-72 CSCD被引 1 次    
16.  Balashov Yu A. On the reserve of mobile rare earth elements in sedimentary rocks. Geochem Int,1969,7:649-658 CSCD被引 1 次    
17.  Parekh P P. Distribution of trace elements between carbonate and non-carbonate phases of limestone. Earth Planet Sci Lett,1977,34:39-50 CSCD被引 8 次    
18.  Drever J I. Weathering processes. Geochemical Processes, Weathering and Groundwater Recharge in Catchments,1997:3-19 CSCD被引 3 次    
19.  Bohn H L. Soil Chemistry,1986:100-115 CSCD被引 2 次    
20.  林传仙. 风化壳淋积型稀土矿床成矿机理的实验研究. 地球化学,1994,23(2):189-198 CSCD被引 22 次    
引证文献 22 篇

1 孙承兴 碳酸盐岩风化壳岩-土界面地球化学特征及其形成过程-以贵州花溪灰岩风化壳剖面为例 矿物学报,2002,22(2):126-132
CSCD被引 44 次

2 李艳丽 贵州平坝白云岩风化壳稀土超常富集层中稀土赋存状态的研究 地球化学,2004,33(6):627-633
CSCD被引 11 次

显示所有22篇文献

论文科学数据集
PlumX Metrics
相关文献

 作者相关
 关键词相关
 参考文献相关

版权所有 ©2008 中国科学院文献情报中心 制作维护：中国科学院文献情报中心
地址：北京中关村北四环西路33号 邮政编码：100190 联系电话：(010)82627496 E-mail:cscd@mail.las.ac.cn 京ICP备05002861号-4 | 京公网安备11010802043238号