摘要
从矿物学、地球化学两个方面对钾质斑脱岩的研究进展进行综合评述。矿物学研究表明,钾质斑脱岩为岩浆成因,由粘土矿物与非粘土矿物组成,粘土矿物以伊-蒙混层矿物和伊利石为主,非粘土矿物包括原生斑晶矿物和次生矿物。钾质斑脱岩的矿物学研究有助于地层对比难题的解决,亦将促进古大陆再造研究。钾质斑脱岩及斑脱岩的主量元素数据统计结果显示,钾质斑脱岩以相对富钾为特征,K2O含量一般大于3.5%。微量元素数据统计表明,钾质斑脱岩的微量元素以Th、U的明显富集为特征,同时均具有负Eu异常并缺乏负Ce异常。通过对早寒武世、奥陶纪及志留纪的钾质斑脱岩的微量元素特征进行对比研究,认为不同时期钾质斑脱岩的微量元素与REE的配分模式表现出不同的特征,尤其是Nb/Y、Th/U等微量元素比值及(La/Yb)N(、La/Sm)N、(Gd/Yb)N、δEu和δCe等稀土元素参数的差异明显。经对比,初步判定滇东石岩头组底部钾质斑脱岩与遵义石岩头组钾质斑脱岩可能不属于同一期火山活动的产物。
Advances in research on K-bentonite have been systematically reviewed in this paper. Mineralogical study of K- bentonite showed that K-bentonite is of magmatic origin and that K-bentonite consists of clay minerals and non-clay ones; the clay minerals are dominated by mixed-layer illite-smectite and illite while the non-clay assemblage is composed of phenocrysts and secondary minerals. Previous major element data for K-bentonites and bentonites in literature were statistically processed. The results suggested that K-bentonite is characteristically rich in K compared with bentonite, and its K2O contents are generally higher than 3.5%. The trace element characteristics of K-bentonite are typified by remarkable Th and U enrichment. Almost all of the K-bentonites yield a negative Eu anomaly , no Ce depletion is recognized in the REE distribution patterns. Comparing the trace element characteristics of Early Cambrian, Ordovician and Silurian K-bentonites, the authors concluded that K-bentonites of different ages have different trace element characteristics. Especially, ratios of Nb/Y and Th/U and REE parameters such as （La/Yb）N, （La/Sm）N, （Gd/Yb）N, δEu and δCe are discriminative. The preliminary correlation shows that K-bentonite at the bottom of the Shiyantou Formation in eastern Yurman cannot be correlated with that from the same formation at Zunyi, Guizhou Province.
出处
《矿物学报》
CAS
CSCD
北大核心
2007年第3期351-359,共9页
Acta Mineralogica Sinica
基金
国家自然科学基金(批准号:40672053)
