[S-CG50] Dynamics in mobile belts

[SCG50-P13] On approximations of EASY%R_o model to estimate maximum experienced temperature from vitrinite reflectance in rocks

*Shunya Kaneki¹, Hiroyuki Noda¹ (1.Disaster Prevention Research Institute, Kyoto University)

Keywords:Vitrinite reflectance, Paleothermal history, EASY%Ro, Approximation

Vitrinite reflectance is one of the most popular thermal indices for rocks. Among various models to estimate paleothermal histories, EASY%R_o has been widely used since proposed by Sweeney & Burnham (1990). Approximations of EASY%R_o solutions employing specific paleothermal histories have been used in the field of structural geology to estimate maximum experienced temperatures from vitrinite reflectance. However, comparisons of those approximations with results obtained with EASY%Ro itself have not been reported in scientific literatures, and the errors of approximations and the limitations of their use to determine maximum temperature remain undocumented. In this study, we performed such comparisons and found that the use of some approximations proposed in the previous studies can lead to considerable deviations from the results obtained with EASY%R_o. We then derived new approximations of EASY%R_o solutions for four representative paleothermal histories that provided estimates of the maximum temperatures within 3 °C of those obtained with EASY%R_o. We also describe the Jacobian of EASY%Ro for each specific paleothermal history, which can be used to propagate errors from vitrinite reflectance to maximum temperatures. We expect that four approximations derived in this study will be useful because of their smaller approximation errors and wider application ranges compared to the previous approximations, although we recommend to calculate EASY%R_o itself if greater precision or particular paleothermal histories other than those assumed in this study are required.