Assessment of fault activity by direct dating of fault gouge

最近的研究强调了利用断裂带中粘土矿物的K-Ar定年来确定断裂年龄的潜力。为了建立断裂带粘土矿物直接定年方法，采用精确分离粘土，结合断层泥样品的矿物特征，采用不加标K-Ar法进行定年。较细的组分产生较年轻的K-Ar年龄，并含有大量的低温型粘土，这表明最近生长的粘土矿物富集。由于K-Ar法测年不能检测到100 ℃以下形成的无钾粘土，因此该年龄代表了>100 ℃温度环境下断裂活动的最晚时间。断层粘土的基础研究和测年要求有待进一步加强。

Recent studies highlighted the potential to determine the age of faulting by using K-Ar dating of clay minerals in fault zone. However, the challenge remains difficult due to the possibility of contamination by old K-bearing minerals of the host rock.In order to establish a direct dating method for clay minerals in fault zone, precise clay separation combined with mineral characterization of fault gouge samples, and dating by unspiked K-Ar method was conducted. The finer fractions yield younger K-Ar ages, and contain larger amount of low-temperature type clay, suggesting enrichment in more recently grown clay minerals. Because K-Ar dating cannot detect no-potassium clay which formed <100 degree C, the ages mean the latest timing of faulting under >100 degree C temperature environment. Further fundamental studies about fault clay and requirements in dating are needed.