吉林省东部石炭—二叠系伊利石的成因标志

Genetic Chariciterics of Illite in the Carboniferous-Permian Pelitic Rocks in East Jilin Province

吉林东部石炭—二叠系主要是一套泥质岩石,其详细深入的矿物学工作尚不多见。利用JSM-6700F场发射电镜及INCA能谱仪,研究了伊利石的显微形貌和微区成分。采用D/max-2500X-射线衍射仪,研究了伊利石的结晶度、多型和b0值。结果表明:研究区伊利石结晶度变化于0.26～0.77,平均值为0.44;伊利石(白云母)多型有3种类型,分别为1Md型、1Md+2M1混合型和2M1型;伊利石(白云母)b0值为8.996～9.045,平均值为9.007。石炭系伊利石结晶度变化于0.26～0.50,平均值为0.35,主要呈2M1多型,b0平均值为9.011,主要是低级近变质带的产物;二叠系伊利石结晶度变化于0.26～0.50,平均值为0.42,主要为1Md+2M1混合型多型,b0平均值为9.004,主要为晚期成岩带的产物。

The Carboniferous-Permian strata in east Jilin is mainly composed of pelitic rocks for which no detailed mineralogical research works have been done up to now.By using JSM-6700F field emission scanning electron microscope and INCA EDS,the authors focused on the micro-morphology and composition of illite,the most important clay mineral of the pelitic rocks.The crystallinity,polytype and b0 dimension of illite were measured using a D/mas-2500X-ray diffractometer.The illite crystallinity ranges from 0.26 to 0.76 and averages at 0.44.The illite polytype of（muscovite） is featured by 1Md,1Md＋2M1 and 2M1 types.The illite（muscovite） b0 dimension ranges from 8.996 to 9.045 and averages at 9.007.The illite crystallinity of the Carboniferous rocks ranges from 0.26 to 0.50,averages at 0.35.Their polytype is predominantly 2M1,averaged b0 dimension is 9.011.These results suggest that the Carboniferous rocks probably were formed in a low anchizone.In contrast,the illite crystallinity of the Permian rocks ranges from 0.26 to 0.50,averages at 0.42,its polytype is mainly 1Md＋2M1,mean b0 dimension is 9.004,indicating a late diagenetic zone.