摘要
对巢湖北部地区以碳酸盐岩为主的寒武系—下三叠统海相地层的黏土矿物分析及伊利石结晶度测定的结果表明:伊利石是本区海相地层的主体矿物,平均体积分数为73%。黏土矿物的成岩转化特征表现为蒙皂石的伊利石化。按照伊利石结晶度的成岩-浅变质程度划分,本区寒武系—下三叠统的成岩作用已达到最高成岩阶段。伊利石结晶度的纵向变化总体上可分为上、下两部分:下部寒武系至志留系的结晶度为0.41～0.60°Δ2θ,结晶度与埋深具有一定的相关性,成岩作用是下部地层黏土矿物特征的主控因素;上部泥盆系至下三叠统的结晶度为0.45～0.77°Δ2θ,呈波动变化,蒙皂石连续出现,地层没有被显著埋藏,沉积因素是上部地层黏土矿物特征的主控因素。下三叠统地层中蒙皂石的分布特征以及上泥盆统五通组顶部高岭石的普遍富集具有重要的古气候研究意义。
Clay mineral study and illite crystallinity determination are performed mainly on Cambrian to lo-wer Triassic marine sedimentary rocks,dominated by carbonates,in north Chaohu region,Anhui Province.The results show that illite,which accounts for 73%,is the forming clay mineral of marine strata in this region.Clay minerals diagenesis is characterized by smectite to illite.According to the diagenesis-very low-grade metamorphism classification,based on illite Kübler index,the strata studied have reached the highest diagenetic stage.The vertical changes of illite crystallinity can be generally divided into the lower part and the upper part.The crystallinity values of the lower part from Cambrian to Silurian vary from 0.41 to 0.60°Δ2θ,which are related with depth.So diagenesis is the controlling factor of the clay mineralogy of the lower part.While the crystallinity values of the upper part from Devonian to Lower Triassic are scattered between 0.45 and 0.77°Δ2θ.Smectite is present in the upper part,implying that the upper part from Devonian to Lower Triassic has not been deeply buried with sedimentation as its controlling factor.The distribution of smectite in Lower Triassic of north Chaohu region as well as the widespread enrichment of kaolinite at the top of Wutong Formation of Upper Devonian is of important significance for the paleoclimate study of this region.
出处
《吉林大学学报（地球科学版）》
EI
CAS
CSCD
北大核心
2011年第S1期169-180,共12页
Journal of Jilin University：Earth Science Edition
基金
国家自然科学基金项目(40621063)
