U-series ages of a set of speleothem samples from the two caves near Tangshan Town, Nanjing, determined by thermal ionization mass spectrometry (TIMS), range from older than 500 KaBP to around 20 kaBP. These dated spe...U-series ages of a set of speleothem samples from the two caves near Tangshan Town, Nanjing, determined by thermal ionization mass spectrometry (TIMS), range from older than 500 KaBP to around 20 kaBP. These dated speleothems with unequivocal stratigraphic layers in cave sediments provide basic data to establish a geochronologic sequence for the展开更多
samples of lava and pumice from the cone of Changbaishan Tianchi Volcano, Jiling, China, were dated by using high precision U-series TIMS method. We conclude that the bottom of the cone formed before 350 ka, the middl...samples of lava and pumice from the cone of Changbaishan Tianchi Volcano, Jiling, China, were dated by using high precision U-series TIMS method. We conclude that the bottom of the cone formed before 350 ka, the middle part in 70～80 ka, the upper during 20～1ka, and the top less than 1ka, and the age based periods of the volcano eruption since Late Pleistocene is given as follows: >350ka,70ka,18～25ka,10ka, 4C5ka, 1～0.75ka, which may offer the basis for the study of volcanic disaster in future. In addition, the principle of dating young volcanic rocks by using U-series TIMS method is introduced briefly. Differentiation characteristics of U and Th in different minerals of the volcanic rocks are discussed, and the ability producing isochrons, based on U and Th differentiation, are discussed. In the last part of the paper, the closure of samples to the elements U and Th, which is important for age results, is discussed by using ( 234 U/ 238 U) radioactivity ratio which can be used to monitor if the samples have been weathered or eroded or leached since the time they formed. In this study, all samples have ( 234 U/ 238 U) activity ratios within 1% of secular equilibrium (( 234 U/ 238 U) radioactivity ratios are unity), indicating no disturbance of the 234 U～ 238 U system. All of these discussions show that the TIMS method is good to date Tianchi volcanics and the results are reliable.展开更多
The ages of coral reef samples from several shallow drill holes in the South China Sea are determined by ESR and U-series (230Th/234U) methods. The experimental results show ideal agreement between ESR and U-series ag...The ages of coral reef samples from several shallow drill holes in the South China Sea are determined by ESR and U-series (230Th/234U) methods. The experimental results show ideal agreement between ESR and U-series ages and that the coral reefs were formed in the early Holocene. In the determination of natural total dose of coral reef by use of the additive dose method good results can be obtained by exponential fitting, no matter how the effect of dose saturation is. It was found that the ratio of the natural ESR signal intensity ( I0) to the ESR signal intensity at dose saturation ( Imax) of sample can reflect the significance of a irradiation efficiency-k value. Using the k value of sample determined by the formula given in this paper, the precision of ESR dating of marine carbonates can be improved.展开更多
A method for age dating of uranium mineral particles by double focusing magnetic sector inductively coupled mass spectrometry (FS-ICPMS) and thermal ionization mass spectrometry (TIMS) was presented. Pb/U ratio in ura...A method for age dating of uranium mineral particles by double focusing magnetic sector inductively coupled mass spectrometry (FS-ICPMS) and thermal ionization mass spectrometry (TIMS) was presented. Pb/U ratio in uranium mineral particles was measured by FS-ICPMS without any chemical separation procedure. Pb isotope composition in uranium mineral particles was determined by TIMS associated with micro column anion exchange resin method. Due to simplified chemical procedure and minimum use of reagents, the full procedure blank was reduced to 230 pg Pb, leading to the successful age dating of uranium mineral particles with relative standard deviation less than 2%.展开更多
Two national stalagmite standard （GBW04412, GBW04413） and one international coral standard （RKM4） have been determined by using thermal ionization mass spectrometry （TIMS） method. The values of （ 234 U/ 238 U）...Two national stalagmite standard （GBW04412, GBW04413） and one international coral standard （RKM4） have been determined by using thermal ionization mass spectrometry （TIMS） method. The values of （ 234 U/ 238 U） act , （ 230 Th/ 234 U） act and age are all consistent in error range with the standard values obtained by using α spectrometry.展开更多
Dating techniques including gypsum dissolution in water, iron hydroxide co-precipitation with uranium and thorium and mass spectrometric determination have been investigated in this note. The ages of the gypsum sample...Dating techniques including gypsum dissolution in water, iron hydroxide co-precipitation with uranium and thorium and mass spectrometric determination have been investigated in this note. The ages of the gypsum samples in a CK core from Luobubo lacustrine sediments are in the range of (12.85±0.21) kaBP (4 m distance from the top core) to (153.2 ± 7.2) kaBP (49 m distance from the top core) with the relative errors of ( 1.6%-±4.7%. It indicates that the sedimental environment of the CK core was situated in the middle-late Pleistocene and Holocene periods, corresponding to 1-6 stages of oxygen isotopes in the abyssal sediments and included much information from last inter-glacial to Holocene warm periods.展开更多
Since the first discovery of eofianite on Shidao Island(Xisha Islands)in 1983, several papers have been published. The basement beneath eolianite on Shidao Island is explicitly separated by a clear erosion surface. It...Since the first discovery of eofianite on Shidao Island(Xisha Islands)in 1983, several papers have been published. The basement beneath eolianite on Shidao Island is explicitly separated by a clear erosion surface. Its age is 70 ka deduced by oxygen stable展开更多
We have pointed out that, after excluding operational errors, the 230Th/234U age of stalagmitic calcite shows a satisfactory internal consistency. However, good precision of the results, together with its coherence wi...We have pointed out that, after excluding operational errors, the 230Th/234U age of stalagmitic calcite shows a satisfactory internal consistency. However, good precision of the results, together with its coherence with stratigraphic sequence, is only a necessary but not a sufficient condition for ascertaining its validity.展开更多
A high precision thermal ionization mass spectrometric (HP-TIMS) technique is used to determine 238U,234U,232Th,230Th concentrations and their ratios in whole rocks and minerals separated from Ouaternary Maanshan, Day...A high precision thermal ionization mass spectrometric (HP-TIMS) technique is used to determine 238U,234U,232Th,230Th concentrations and their ratios in whole rocks and minerals separated from Ouaternary Maanshan, Dayingshan and Heikongshan volcanic rocks of Tengchong volcanic field .Yunnan Province, China. The 238U-230Th isochrons are given, yielding four age values (227 ? 20) ka (D-1, Dayingshan), (79.6 ±5.5) ka (D-7, Dayingshan), (21.9 ± 3.0) ka (h-1, Heikongshan), and (7.5 ± 1.0) ka (M-1, Maanshan). The result is not only consistent with but also preciser than those measured by the K-Ar method and the alpha spectrometry U-series method, indicating that the HP-TIMS method is reliable and has high precision. Besides, a procedure of HP-TIMS analysis of young volcanic rocks in China is set up preliminarily.展开更多
The U-series component-dating method has been employed to date the sediment core B-194 from Balikun Lake. 230Th/ 232Th and 234U/ 232Th ratios in various components of the samples dissolved in different concentration a...The U-series component-dating method has been employed to date the sediment core B-194 from Balikun Lake. 230Th/ 232Th and 234U/ 232Th ratios in various components of the samples dissolved in different concentration acids were measured respectively. The results indicate that there is a good relationship of the isotopic ratios between the solutions and the residues, and that uranium and thorium isotopic fractionations did not occur during acid leaching. Based on the U-series ages obtained by using component-dating method, a 144-ka time sequence was established corresponding to the upper 25-m interval of the B-194 core, which is in agreement with palaeomagnetic dating results. The fact that the palaeoclimatic and palaeoenvironmental record labeled with U-series ages is correlative with the deep-sea δ 18O SPECMAP also demonstrates that the U-series component-dating method can be used to date lake sediments.展开更多
文摘U-series ages of a set of speleothem samples from the two caves near Tangshan Town, Nanjing, determined by thermal ionization mass spectrometry (TIMS), range from older than 500 KaBP to around 20 kaBP. These dated speleothems with unequivocal stratigraphic layers in cave sediments provide basic data to establish a geochronologic sequence for the
文摘samples of lava and pumice from the cone of Changbaishan Tianchi Volcano, Jiling, China, were dated by using high precision U-series TIMS method. We conclude that the bottom of the cone formed before 350 ka, the middle part in 70～80 ka, the upper during 20～1ka, and the top less than 1ka, and the age based periods of the volcano eruption since Late Pleistocene is given as follows: >350ka,70ka,18～25ka,10ka, 4C5ka, 1～0.75ka, which may offer the basis for the study of volcanic disaster in future. In addition, the principle of dating young volcanic rocks by using U-series TIMS method is introduced briefly. Differentiation characteristics of U and Th in different minerals of the volcanic rocks are discussed, and the ability producing isochrons, based on U and Th differentiation, are discussed. In the last part of the paper, the closure of samples to the elements U and Th, which is important for age results, is discussed by using ( 234 U/ 238 U) radioactivity ratio which can be used to monitor if the samples have been weathered or eroded or leached since the time they formed. In this study, all samples have ( 234 U/ 238 U) activity ratios within 1% of secular equilibrium (( 234 U/ 238 U) radioactivity ratios are unity), indicating no disturbance of the 234 U～ 238 U system. All of these discussions show that the TIMS method is good to date Tianchi volcanics and the results are reliable.
文摘The ages of coral reef samples from several shallow drill holes in the South China Sea are determined by ESR and U-series (230Th/234U) methods. The experimental results show ideal agreement between ESR and U-series ages and that the coral reefs were formed in the early Holocene. In the determination of natural total dose of coral reef by use of the additive dose method good results can be obtained by exponential fitting, no matter how the effect of dose saturation is. It was found that the ratio of the natural ESR signal intensity ( I0) to the ESR signal intensity at dose saturation ( Imax) of sample can reflect the significance of a irradiation efficiency-k value. Using the k value of sample determined by the formula given in this paper, the precision of ESR dating of marine carbonates can be improved.
文摘A method for age dating of uranium mineral particles by double focusing magnetic sector inductively coupled mass spectrometry (FS-ICPMS) and thermal ionization mass spectrometry (TIMS) was presented. Pb/U ratio in uranium mineral particles was measured by FS-ICPMS without any chemical separation procedure. Pb isotope composition in uranium mineral particles was determined by TIMS associated with micro column anion exchange resin method. Due to simplified chemical procedure and minimum use of reagents, the full procedure blank was reduced to 230 pg Pb, leading to the successful age dating of uranium mineral particles with relative standard deviation less than 2%.
文摘Two national stalagmite standard （GBW04412, GBW04413） and one international coral standard （RKM4） have been determined by using thermal ionization mass spectrometry （TIMS） method. The values of （ 234 U/ 238 U） act , （ 230 Th/ 234 U） act and age are all consistent in error range with the standard values obtained by using α spectrometry.
基金This work was supported by the National Key Basis Research Project (Grant No. G19990434) the Innovative Project of the Chinese Academy of Sciences (Grant No. KZCX 1-y 05) and the Resources and Environment Basis Project of the University of Science an
文摘Dating techniques including gypsum dissolution in water, iron hydroxide co-precipitation with uranium and thorium and mass spectrometric determination have been investigated in this note. The ages of the gypsum samples in a CK core from Luobubo lacustrine sediments are in the range of (12.85±0.21) kaBP (4 m distance from the top core) to (153.2 ± 7.2) kaBP (49 m distance from the top core) with the relative errors of ( 1.6%-±4.7%. It indicates that the sedimental environment of the CK core was situated in the middle-late Pleistocene and Holocene periods, corresponding to 1-6 stages of oxygen isotopes in the abyssal sediments and included much information from last inter-glacial to Holocene warm periods.
文摘Since the first discovery of eofianite on Shidao Island(Xisha Islands)in 1983, several papers have been published. The basement beneath eolianite on Shidao Island is explicitly separated by a clear erosion surface. Its age is 70 ka deduced by oxygen stable
文摘We have pointed out that, after excluding operational errors, the 230Th/234U age of stalagmitic calcite shows a satisfactory internal consistency. However, good precision of the results, together with its coherence with stratigraphic sequence, is only a necessary but not a sufficient condition for ascertaining its validity.
文摘A high precision thermal ionization mass spectrometric (HP-TIMS) technique is used to determine 238U,234U,232Th,230Th concentrations and their ratios in whole rocks and minerals separated from Ouaternary Maanshan, Dayingshan and Heikongshan volcanic rocks of Tengchong volcanic field .Yunnan Province, China. The 238U-230Th isochrons are given, yielding four age values (227 ? 20) ka (D-1, Dayingshan), (79.6 ±5.5) ka (D-7, Dayingshan), (21.9 ± 3.0) ka (h-1, Heikongshan), and (7.5 ± 1.0) ka (M-1, Maanshan). The result is not only consistent with but also preciser than those measured by the K-Ar method and the alpha spectrometry U-series method, indicating that the HP-TIMS method is reliable and has high precision. Besides, a procedure of HP-TIMS analysis of young volcanic rocks in China is set up preliminarily.
文摘The U-series component-dating method has been employed to date the sediment core B-194 from Balikun Lake. 230Th/ 232Th and 234U/ 232Th ratios in various components of the samples dissolved in different concentration acids were measured respectively. The results indicate that there is a good relationship of the isotopic ratios between the solutions and the residues, and that uranium and thorium isotopic fractionations did not occur during acid leaching. Based on the U-series ages obtained by using component-dating method, a 144-ka time sequence was established corresponding to the upper 25-m interval of the B-194 core, which is in agreement with palaeomagnetic dating results. The fact that the palaeoclimatic and palaeoenvironmental record labeled with U-series ages is correlative with the deep-sea δ 18O SPECMAP also demonstrates that the U-series component-dating method can be used to date lake sediments.
