Doğal kalsit minerallerinin termolüminesans ve ser yöntemleriyle incelenmesi ve tarihlenmesi
Termoluminescence and esr studies and dating of natural calcite minerals
- Tez No: 55348
- Danışmanlar: PROF.DR. GÜVEN OLGUN
- Tez Türü: Doktora
- Konular: Fizik ve Fizik Mühendisliği, Physics and Physics Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1996
- Dil: Türkçe
- Üniversite: Hacettepe Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 232
Özet
VI ABSTRACT In this study, the calcite type travertine smaples collected from Denizli and Çankırı regions, were investigated and dated by Thermoluminescence (TL) and Electron Spin Resonance (ESR) Spectroscopy. On the natural glow curves of Denizli and Çankırı travertines, two glow peaks were observed at 280°C, 330°C and at 270°C, 330°C respectively. Upon irradiating the samples artifically, additional glow peaks at 180°C and 170°C were observed in Denizli and Çankırı travertines respectively. Heating of the samples before irradiation, caused an increase in the thermoluminescence sensitivity for all peaks, except the one at 330°C. It was also found that this increase depends on both pre-heating temperature and time. An attempt was made to explain this increase in sensitivity by increasing of the rate of diffusion of impurity ions in the crystal during heating. The relationship between thermoluminescence sensitivity and pre-irradiation dose was also examined, and beyond a threshold value of pre-irradiation dose, an increase in the thermoluminescence sensitivity of all peaks, except the one at 330°C was found for every samples. As the glow peaks at 330°C were saturated at very low artificial dose values for the dating purpose the peaks at 280°C and 270°C were used in Denizli and Çankırı travertines, respectively. It was found that the thermal life time of the trapped electrons, x, corresponding to these peaks, is about 107 years. It is therefore concluded that the samples older than 106 years could be dated by using these glow peaks. In order to investigate the alteration of thermoluminescence glow peak intensity with irradiation dose virgin travertines and samples consolidated with impregnated polymers were irradiated and the growth curves were obtained. ED (Equivalent Dose) and JD (Geological Dose) values were calculated using the Barabas model and the least square method. It was found that the values found both for natural and consolidated samples were in good correlation within the limits of confidence.VII Furthermore, it was also found that these values were not effected from different dose rates. Annual dose of the samples were calculated by combining the results of two methods which give internal and external doses received. To determine internal dose rate, the amount of radioactive elements, 238U, 232Th and 40K in the samples were measured. Neutron activation analysis was performed for this measurement. For external dose rate measurement CaSO^Dy dosimeters were used. The ages of each travertine sample were thus calculated by using annual dose, ED and JD values. The age of Denizli travertine is determined to be 774.000 T 66.000 years and that of Çankırı travertine is 103.000 T 9.000 years. The ESR spectra of the same samples were also taken at room temperature. The ESR signals in the spectra were assigned to CO3“3, CO3”and CO2“ centres that were originated from the ionization of CO3”2 groups, which is the major constituent of calcite after irradiation. The heating of irradiated samples at different temperatures above room temperature for equal periods showed that 180°C, 280°C peaks in Denizli travertines and 1 70°C, 270°C glow peaks in Çankırı travertines are correlated with CO3“3 and CO2' centres as well as the peaks at 330°C are correlated with CO3”centers. The ages of the same samples were also calculated by ESR method and the ages of Denizli and Çankırı travertines are found to be 1.110.000 T 110.000, 230.000 T 22.000 years respectively. The differences in ages determined by these two methods are explained by the nature of thermoluminescence method. The decreasing of the luminescence emission sensitivity of the trapped electrons with respect to different parameters is assumed to be the main reason for the low value obtained by thermoluminescence.
Özet (Çeviri)
VI ABSTRACT In this study, the calcite type travertine smaples collected from Denizli and Çankırı regions, were investigated and dated by Thermoluminescence (TL) and Electron Spin Resonance (ESR) Spectroscopy. On the natural glow curves of Denizli and Çankırı travertines, two glow peaks were observed at 280°C, 330°C and at 270°C, 330°C respectively. Upon irradiating the samples artifically, additional glow peaks at 180°C and 170°C were observed in Denizli and Çankırı travertines respectively. Heating of the samples before irradiation, caused an increase in the thermoluminescence sensitivity for all peaks, except the one at 330°C. It was also found that this increase depends on both pre-heating temperature and time. An attempt was made to explain this increase in sensitivity by increasing of the rate of diffusion of impurity ions in the crystal during heating. The relationship between thermoluminescence sensitivity and pre-irradiation dose was also examined, and beyond a threshold value of pre-irradiation dose, an increase in the thermoluminescence sensitivity of all peaks, except the one at 330°C was found for every samples. As the glow peaks at 330°C were saturated at very low artificial dose values for the dating purpose the peaks at 280°C and 270°C were used in Denizli and Çankırı travertines, respectively. It was found that the thermal life time of the trapped electrons, x, corresponding to these peaks, is about 107 years. It is therefore concluded that the samples older than 106 years could be dated by using these glow peaks. In order to investigate the alteration of thermoluminescence glow peak intensity with irradiation dose virgin travertines and samples consolidated with impregnated polymers were irradiated and the growth curves were obtained. ED (Equivalent Dose) and JD (Geological Dose) values were calculated using the Barabas model and the least square method. It was found that the values found both for natural and consolidated samples were in good correlation within the limits of confidence.VII Furthermore, it was also found that these values were not effected from different dose rates. Annual dose of the samples were calculated by combining the results of two methods which give internal and external doses received. To determine internal dose rate, the amount of radioactive elements, 238U, 232Th and 40K in the samples were measured. Neutron activation analysis was performed for this measurement. For external dose rate measurement CaSO^Dy dosimeters were used. The ages of each travertine sample were thus calculated by using annual dose, ED and JD values. The age of Denizli travertine is determined to be 774.000 T 66.000 years and that of Çankırı travertine is 103.000 T 9.000 years. The ESR spectra of the same samples were also taken at room temperature. The ESR signals in the spectra were assigned to CO3“3, CO3”and CO2“ centres that were originated from the ionization of CO3”2 groups, which is the major constituent of calcite after irradiation. The heating of irradiated samples at different temperatures above room temperature for equal periods showed that 180°C, 280°C peaks in Denizli travertines and 1 70°C, 270°C glow peaks in Çankırı travertines are correlated with CO3“3 and CO2' centres as well as the peaks at 330°C are correlated with CO3”centers. The ages of the same samples were also calculated by ESR method and the ages of Denizli and Çankırı travertines are found to be 1.110.000 T 110.000, 230.000 T 22.000 years respectively. The differences in ages determined by these two methods are explained by the nature of thermoluminescence method. The decreasing of the luminescence emission sensitivity of the trapped electrons with respect to different parameters is assumed to be the main reason for the low value obtained by thermoluminescence.
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