蒙皂石伊利石化反应机理和框架性行为模式

对珠江口盆地两口钻井95个泥质岩样粘土矿物X衍射分析资料的定量研究表明,若反应是以消耗蒙皂石为代价形成伊利石,则反应符合溶解-沉淀机理,但除此以外,蒙皂石还可以净溶解或新增伊利石层的方式加大I/S比。蒙皂石在渐进成岩过程中的框架性行为模式具有三级控制,按顺序分别由温度、基本离子成分和动力学因素控制特定温度段内蒙皂石行为过程的起始和终结、行为过程的方式和行为过程的速率和程度。渐进成岩过程中I/S比的变化主要与第三级控制有关,而游离状蒙皂石和伊-蒙混层粘土的含量变化则是第二三两级共同控制的结果。

SMECTITE ILLITIZATION REACTION MECHANISM AND FRAMEWORK MODEL OF ITS BEHAVOURS

Based on the XRD data of clay minerals of 95 argillite samples from two wells in the Zhujiangkou Basin a quantitative study is made to the changes between sections in weight percentages of discrete smectite and illite and smectite layers and illite layers in the mixed layer illite/smectite.The result indicates that the reaction accords with the dissolution/precipitation mechanism if the illite formed at the expense of smectite.Ex cepting this,however,smectite can also increase I/S ratio by net dissolution or adding illite layers within itself.The framework model of smectite behavours in progressive diagenesis processes is of three order controls,by order,the temperature,essential ion con stiutent and kinetic factors control the smectite behavours on thebeginning and termination,the way and the proceeding rate and degree,respectively,in an appointed zone of temperature.The I/S ratio showed in a given temperature in the nature is almost always less than that of being stable in the temperature and is therefore metastable.Consequently it would get reach to a stable higher value during the progressive diagenesis,along with which any change in I/S ratio is relative mainly to the kinetic factors(the third order control),and any change in content of the discrete smectite and mixed layer illite/smectite is resulted from the essential ion constituent(the second order control)in association with thekinetic factors.Details of the controls in deeper level are not involved in the model,but it would propose a direction significant for understanding the smectite behavours in diagenesis processes and determining the change in diagenetic sys tem based upon the behavours.