| An analytical model of EPR dating using E1′, NBOHC and middle peak has been developed through modification of the model presented by Barabas et al. (1988). The differential equation for the change of the ESR signal S with time t is given as: dS/dT=cPK-S +k-S/t. Atomic displacement occurs in high dose radiation (above 107 to 108 rads). Coefficients of E1′ are determined by simulation. The mean c and of E1′ are 8.67 × 10−8 and 3.21 × 10 −8, respectively. The ratio c/ is equal to 2.70, which indicates precursors play a more important role in the formation of E1′ than do atomic displacement by radiation. The formation of E1′ through atomic displacement dominates the formation of E1′ through filling the precursors after the saturation level is reached. External - and -rays can create oxygen vacancies in quartz. The traditional additive-dose technique can be only used accurately to date very younger rocks (less than 1 Ma). The reason is given in detail and new method has been developed to date rocks up to 1400 Ma.; The thermal stabilities of E1′, [GeO 4/Li+]0, NBOHC, and the peroxy radical centers are studied in detail. E1′, NBOHC and peroxy radical are determined by production rate, and growth and decay due to thermal annealing. The net result of thermal annealing is obtained and expressed as the following equation: Intensity=I0 +Imax-I0 ×1-exp-growthr -ate×time ×exp-decayr-ate× time, where Imax is the maximum value that can be reach by thermal annealing, I0 the original value before thermal annealing. Imax is dependent on the thermal annealing temperature. The ratio of the maximum signal Imax of E1′ obtained in thermal annealing to the original signal of E1 ′ is limited by its lower boundary (1.0) and its upper boundary (4.54). E1′ doesn't grow when the thermal-annealing temperature is below 56°C and E1′ reaches its maximum limited by all of its precursors being filled at 286°C. The effect of thermal annealing on E1′ is confirmed by high temperature irradiation using the data presented by Wieser et al. (1989), isothermal annealing at 300°C and isochronal thermal annealing from 100°C to 450°C. |
