Clay Minerals Research And Application: As Geothermometers

Paleotemperature may provide useful information for resource exploration. Clay minerals can be used to indicate temperature. Two aspects of clay minerals geothermometer : theory research and practical application were separately expatiated. Theory aspect: illite crystallinity, chlorite composition and other methods for paleotemperature studying were summarized and commented. Illite temperature sensitivity was studied by laser Raman spectrometer. Raman spectrum be analyzed and some new cognitions were found: under 200℃, Raman peaks of illite in low wave numbers band have weak temperature sensitivity; In the main, near 3695cm-1 Raman peak would be red shift with temperature increasing. but whole process can be divided into 3 stages, i.e. between 60~110℃red shift , between 110~130℃small-scale blue shift, and between 130~200℃red shift renewedly. According to Raman shift formula and crystal structure of illite, reason of 3 different shift stages was analyzed. The relationship of temperature and Raman peak's position can be approximate expressed by three straight line equations. The width of hydroxyl-stretching band region would be shortening and the area ratio of OH vibration peaks would be rising with the temperature increasing. By multiple-parametric fitting regression, a mathematical function between temperature and Raman parameters was established. That is a Raman spectrum geothermometer of illite. It was fit for 60~200℃. So, it can be used in sedimentary basins. On the other hand, geothermometer of clay minerals theory which included illite crystallinity, illite Raman spectrum, chlorite composition was applied in Weibei sag. It was calculated the temperature that strata from 2625m to 3456m in chang67 well experienced was about 110~146℃, palaeothermal gradient was 4.0~4.2℃/100m. At the same time, fluid inclusions and vitrinite reflectance also were applied to research paleotemperature in this area. Results verify several temperatures were coincided. Therefore, the applied effect of clay minerals geothermometer was not bad. Contrast present temperature, Weibei sag was cooling gradually.