Abstract
We attempt to apply K-Ar dating to extracted smectite from bentonite formations collected by different age formations from Japan, China, and America. The results show that the K-Ar ages of smectite are younger than the expected geological age estimated from the stratigraphic data or other research data. The time differences increase with increased age, and K-Ar ages in this study also increase with increased age. For example, smectite in the old strata of bentonite has an older age than smectite in the young strata. K-Ar dating by smectite has the greatest potential for indicating the crystallized age of smectite.
Highlights
Smectite is crystallized by diagenesis and hydrothermal alteration in nature and is produced in fault gouges
Illite layers crystallized from smectite layers progress with the potassium fixation process in the interlayer increases with formation temperature
The mixed layer clay that consists of 80% smectite and 20% illite layers (g = 0) (I/S) is generally identified as pure smectite, and it is rare for smectite to not have potassium
Summary
Smectite is crystallized by diagenesis and hydrothermal alteration in nature and is produced in fault gouges. The dating of smectite has significance for mining and evaluating fault activity. The K-Ar dating of smectite is difficult to analyze because smectite does not include potassium. Illite layers crystallized from smectite layers progress with the potassium fixation process in the interlayer increases with formation temperature. The potassium fixation at early alteration mainly occurs by the solid–solid exchange, and the reaction progresses the dissolution-precipitation reaction and increases the illite layers [1]. The mixed layer clay that consists of 80% smectite and 20% illite layers (g = 0) (I/S) is generally identified as pure smectite, and it is rare for smectite to not have potassium
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