Investigation of chloritization of smectite in natural environment

Oba, Takanobu*

The purpose of investigation is as follows :(1) and (2). (1) The observation of the occurrence of chlorite and illite in Tertiary formations of Niigata prefecture. (2) The preliminary experiment of the stability of smectite in iron-rich bulk composition under oxygen fugacity. In the present study, the results are as follows: Mg/(Mg+Fe) ratio and Si of chlorite in the Tertiary sediment increase with depth in the Oguni well of Japan National Oil Corporation. The chemical variation of chlorite suggests that chlorite is rich in iron, in early burial diagenesis. At 350C, montmolorillonite decomposed to quartz, on the other hand saponite break decomposed to a 1:1 regularly interstratified mineral, corrensite with 31.9, mica/smectite interstratified mineral with 27.8 and quartz. As compared with montmolorillonite and saponite, saponite is unstable at low temperature.