粘土矿物在四川盆地须家河组沉积环境研究中的应用

Application of Clay Minerals in Sedimentary Environmental Research of Xujiahe Formation in Sichuan Basin

四川盆地须家河组粘土矿物主要为伊利石和绿泥石,其次为高岭石。通过粘土矿物中硼和钾元素含量的测定,采用国际通用的方法计算了须家河组沉积时的古盐度。认为须家河组沉积初期到未期,水介质性质有明显变化,须二段为真盐水-超盐水、须三～须四段为中盐水、须五段为中盐水-少盐水、须六段为少盐水。通过与其他沉积相标志相结合,认为须家河组沉积期是一个沉积水体由海相高盐度向陆相低盐度转化的过程。须一段沉积期为海陆过渡环境,古盐度值较高。须二段沉积期,古盐度仍然很高,但沉积环境已由海相转化为陆相。须三～须六段沉积期,古盐度总体下降,但须三～须四段沉积期古盐度降低较慢,而须五～须六段沉积期古盐度快速下降。

Clay minerals of Xujiahe Formation in Sichuan Basin were dominated by illite and chlorite,the nest was kaolinite.Based on the determination of boron and potassium contents of clay minerals,calculation of the palaeosaltiness in the deposition period of Xujiahe Formation was carried out by using international methods.It was considered that the water property of Xujiahe Formation changed obviously from the early to late period of deposition in Sichuan Basin with super-saline water in the 2nd member of Xujiahe Formation,medium salt water in the 3rd and 4th member,medium and oligohaline water in the 5th member and oligohaline water in the 6th member.In combination with other symbols of sedimentary facies,it can be concluded that there exists a process of transformation from high palaeosaltiness of marine facies to lower palaeosaltiness of continental facies.Stage 1 of Xujiahe Formation is controlled by marine sedimentary environment with high palaeosaltiness.The palaeosaltiness of Stage 2 is still higher,the sedimentary facies is changed into continental facies from marine facies.The palaeosaltiness is generally reduced from Stage 3 to 6 of Xujiahe Formation,and it is slowly reduced from Stage 3 and 4 and it is quickly reduced from Stage 5 to 6 of Xujiahe Formation.