成岩伊利石K-Ar年龄分析及其意义

Diagenetic Illite K-Ar Age Analysis and Its Significance

烃源岩何时达到最高温度以及其经历加热时与成油构造的时间关系 ,一直是油气勘探研究中的关键问题。成岩伊利石的K Ar年龄可以用来确定碳氢化合物的形成时间 ,但由于无法将成岩伊利石从沉积岩中单独分离出来 ,因此烃源岩达到最高温度的时间一直不能确定。伊利石K Ar年龄分析 (IAA)方法的建立 ,使成岩伊利石年龄的获得成为可能。利用该方法对塔里木盆地某地区 2 772m处的奥陶系烃源层达到最高温度的时代进行了分析 ,结果表明 ,该地层是在上志留纪(40 8Ma)

The timing of hydrocarbon generation is of particular concern in resource exploration. When were the solid organic matters heated to form oil and gas? Because illite forms in rocks in response to heating in the same temperature range as oil formation, its K Ar age is an important parameter. Illite in reservoir sedimentary rocks is a mixture of detrital and diagenetic components. Defining reliable diagenetic ages of illitization in sedimentary rocks still remains a formidable challenge because separation of the diagenetic component is impossible, even if it is carried out down to the grain size as small as <0.02μm. Illite age analysis (IAA, Pevear, 1992) provides a methodology for estimating the diagenetic ages of illite. This paper describes this method and its application in interpreting the K Ar age of illite for a sample from the depth of 2772 m in the Talimu basin. The diagenetic age of illite was determined at 408 Ma. It demonstrates that the maximum geothermal regime was reached in the early Silurian epoch.