重庆中梁山和广元上寺P-T界线粘土层中粘土矿物的类型及成因

四川重庆中梁山和广元上寺P-T界线处二叠系顶部的粘土岩主要由规则混层伊利石-蒙脱石组成,而三叠系底部的粘土岩主要由伊利石和混层绿泥石-蒙脱石组成。形成二叠系顶部规则混层伊利石-蒙脱石并使之得以保存的相对酸性成岩介质可能与晚二叠世生物相对繁盛和绝灭造成的有机质埋藏有关,而三叠系底部的粘土矿物则与相对富镁、钾的成岩介质有关。此外,两地混层伊利石-蒙脱石中混层比例的差别还反映了这一等时面上所经历的最大古地温的差别,这与它们所经历的埋藏史的不同有关。

CLAY MINERALS IN CLAY ROCKS NEAR P/T BOUNDARY FROM GUANGYUAN AND CHONGQING, SICHUAN

The clay minerals in clay rocks near the P/T boundary of Guangyuan and Chongqing,Sichuan were analysed with X-ray diffraction. The clay rock of uppermost Permian is composed of or-dered interstratified illite/montmorillonite and that of lowermost Triassic is composed of illite and in-terstratified chlorite/montmorillonite. Each of these two claystones has its own forming conditions. Therelatively acidic diagenetic agent, favourable to the formation and preservation of ordered interstratifiedillite/montmorillonite, is proposed to be relatal to the mass extinction event which is responsible for theburial of abundant organic materitals during the later Permian. In addition, the difference between com-position of interstratified illite/montmorillonite from Guangyuan and that from Chongqing shows themaximum paleogeothermal difference of the isochronous P/T boundary. It is resulted from the differ-ent buried diagenetic histories between the both regions.