黑色页岩风化剖面母岩均一性的验证

利用风化剖面为研究对象厘定基岩风化过程中元素的地球化学行为,一个潜在的前提假设是风化剖面母岩的化学组成是均一的。以湘西梅城剖面(MC)为例,尝试引入地球化学基因示踪技术,对黑色页岩风化剖面母岩的均一性进行验证,评价其指示效果,并与传统的惰性元素对比值法进行了比较。结果表明,由CIA(chemical index of alteration)值揭示出MC剖面母岩存在异质的客观事实,与地球化学基因的指示结果高度吻合。对于黑色页岩风化剖面的母岩均一性验证,地球化学基因可能是一种有效的示踪技术。与惰性元素对比值法相比,地球化学基因涉及的元素众多(11项),从而弱化了单个元素在基因相似度计算中的权重。个别元素的异常分布对基因相似度评价结果不会产生明显影响,但可以导致元素对比值的显著变化。

Verification of Parent Rock Chemical Homogeneity for Weathering Pofile of Black Shale

To determine elemental geochemical behavior during weathering of bedrock taking weathering profile as the researth object, a potential premise is that the parent rock chemical composition of weathering profile is homogeneous. Selecting a weathering profile (i.e., MC) in Meicheng town, western Hunan Province as an example, this paper attempted to introduce a source tracing technique called geochemical gene to verify parent rock chemical homogeneity for weathering profile of black shale, evaluate its tracing effect, and compare it with the traditional tracing method like the ratio of inert element pair. The results show as follows. The CIA values reveal the fact that parent rock of the profile MC is heterogeneous, which is highly consistent with the tracing result from the geochemical gene. Geochemical gene is an effective tracing technique for the verification of parent rock chemical homogeneity of weathering profile of black shale. Compared with the ratio of inert element pair which contains two elements, geochemical gene involves a lot of elements (up to 11 items), which weakens the weight of single element in gene similarity calculation. The abnormal distribution of individual elements has no obvious effect on the evaluation result of gene similarity, but may lead to significant change in the ratio of element pair.