烃包裹体赋存矿物ESR测年及成藏期次研究——以塔北地区寒武系—奥陶系为例

ESR dating method of hydrocarbon inclusions-hosting minerals and its application in timing of hydrocarbon accumulation: a case study of Cambrian-Ordovician reservoirs in the northern Tarim Basin

电子自旋共振(ESR)测年方法是近年来引入石油地质领域的一种新方法,该方法根据顺磁中心浓度与成矿年龄及岩石放射性元素含量的关系,确定矿物颗粒的结晶年龄,可应用于含原生烃包裹体赋存矿物石英测年。通过塔北地区样品镜下观察,以及取自不同期次含原生烃包裹体的石英脉样品ESR测年分析,结合前人自生伊利石K—Ar同位素测年成果,厘定了塔北地区油气成藏时间。研究结果表明塔北地区具多期成藏特点:第一期以发褐色荧光液态烃包裹体为主,成藏时间为376Ma(加里东晚期—海西早期);第二期以发黄色荧光气液烃包裹体为主,成藏时间为293.49—242.0Ma(海西晚期);第三期以发蓝色荧光的气液烃包裹体为主,成藏时间为49—32.8Ma(喜马拉雅早期);第四期在局部发育黑色气态烃包裹体,成藏时间为24.0—8.5Ma(喜马拉雅晚期)。

The Electron Spin Resonance（ESR） dating method introduced into petroleum geology recently can detect the crystallization age of mineral grains such as the quartz hosting primary hydrocarbon inclusions, based on the correlation of paramagnetic center concentration with mineralization age and the content of radioactive elements. The hydrocarbon accumulation periods in the northern Tarim Basin were identified based on microscopic observation of rock samples taken from the northern Tarim Basin, ESR dating results of quartz vein samples with primary hydrocarbon inclusions in different stages, and previous K-Ar dating results of authigenic illite samples. The results show that hydrocarbon accumulation in the northern Tarim Basin were developed in four periods. The first primary hydrocarbon inclusions are liquid with brown fluorescence, and generated in 376 Ma（Late Caledonian to Early Hercynian）. The second are liquid with yellow fluorescence, and generated from 293.49 to 242.0 Ma（Late Hercynian）. The third are gas-liquid with blue fluorescence, and generated from 49 to 32.8 Ma（Early Himalayan stage. The fourth are local gas inclusions in black, and generated from 24.0 to 8.5 Ma（Late Himalayan）.