摘要
本文以两种典型风化壳剖面为例，对风化壳中稀土元素的分布和形成特征进行了讨论。研究认为，它们在风化壳中的富集和分异，受风化壳的结构、土的物理和水理性质、化学和矿物成分以及成土过程和成土作用的控制。简言之，系喀斯特成土作用的结果。
Rare earth element(REE) is an important “Indicator and Tracer” of geochemical reaction. So the study on the REE distribution in the carbonate weathering crusts in Guizhou can be helpful for us to understand the soil formation and genesis. We have some conclusions as follows: 1)The REE contents on the lateritic weathering profile are much higher than those in other kinds of weathering crusts. The total amount of REE (ΣREE) in the laterite may reaches to (537.76￣704.55)*10 -6 which is 12～30 times as much as ΣREE in their bedrock. The enrichment of ΣREE is so high that it could not originate from their bedrock.Actually, the REE were brought by the groundwater and accumulated in the process of soil formation. 2)The vertical zoning of REE in carbonate weathering profiles is obvious, which is quite different from that in other kinds of weathering crusts. The lower the laterite is in a profile,the higher the REE enriches. The richest layer of REE is on the variegated aureole layer. 3)According to some parameters of REE and standardized maps of REE distribution of 22 samples, the contents of REE in bedrocks are very low,and a little higher. Both layers are poor in REE comparing with the standard REE contents in North American Shale Composite(NASC), so their curves are at the bottom of the maps.In the ferruginous crust or variegated aureole layer, the contents of REE are much higher.So the curves are located at the top of the maps. 4)The rare earth element distribution in the lateritic layers shows that there are three stages in the process of their formation, namely, enrichment, fractionation and dilution. The variegated aureole layer,on the interface between laterite and bedrock, is recently developed. All elements of REE and ΣREE are enriched in this layer. Upwards from this layer to surface,the contents of REE are decreased and fractionated. Up to the soil,the contents of REE are leached and diluted further,and gradually reach to the standard volume of NASC. 5)ΣREE in the iron and the iron manganese crust is the highest or much higher than that in the surrounding laterite.
出处
《中国岩溶》
CAS
CSCD
1998年第1期15-24,共10页
Carsologica Sinica
基金
国家自然科学基金
贵州省科学基金
关键词
碳酸盐岩
风化壳
贵州
稀土族
分布特征
Weathering crust of carbonate rock Rare earth element Distribution Guizhou Province
