沉积岩中自生伊利石K-Ar定年研究——存在问题及原因讨论

Study on the K-Ar Dating of Diagenetic Illite in Sedimentary Rock Samples——Question and Discussion

摘要: 在浙江长兴煤山全球二叠系一三叠系界线层型剖面中界线附近采集黏土岩样品。对其中的伊利石／蒙皂石成岩间层I／S进行K—Ar测年实验研究，来探讨沉积岩中自生伊利石K—Ar测年在确定沉积地层时代方面的可行性。结果表明，沉积岩中成岩间层I／S的K—Ar年龄在没有碎屑含钾矿物混入的情况下，比其对应的地层时代要年轻，其原因主要有两条，一是因为泥岩中的自生伊利石来自于蒙皂石的伊利石化，而蒙皂石的伊利石化受很多因素控制，需要一定的时间才能完成；另一原因是由于蒙皂石伊利石化过程中存在着放射性成因^40Ar的扩散丢失。

Abstract: The diagenetic I/S of P-T boundary in Changxing,Zhejiang province was dated using K-Ar method. The results show that the K-Ar ages of pure diagenetic L/S is younger than the age of the P-T boundary.The rea- sons for this result are that(1)the diagenetic illite in mudstone is formed through the sluggish smectite illitiza- tion,and(2)the loss of the radiogenic~(40)Ar exists in the fine clay minerals during the smectite illitization.