Isotopic data on drill hole water and surface water samples from the Yengbajain geothermal area as well as an ice sample from the glacial amphitheater in the Mt. Nyainqintanglha to the northwest of the Yangbajain basi...Isotopic data on drill hole water and surface water samples from the Yengbajain geothermal area as well as an ice sample from the glacial amphitheater in the Mt. Nyainqintanglha to the northwest of the Yangbajain basin are presented in this paper. In consideration of isotopic fractionation during steam separation, the hydrogen and oxygen isotopic ratios for thermal waters collected at the mouths of drill holes have been calibrated. The D/H ratio of thermal waters is similar to that of local precipitation, indicating their meteoric origin. The δ D and δ^18O values of the thermal waters of --150--160 and -17-20‰, respectively are the lowest among those well-known geothermal fields in the world.The recharge area of the geothermal system is at elevation of about 4,800--5,000 m. Drill holes along the axis of a tongueshaped zone where loose Quaternary sediments have been cemented by siliceous material show greater δ D and δ^18O values and discharge tritiumfree thermal waters. It is suggested that the thermal waters may be derived from superhcated water and steam which find their way upwards along the tectonic fractures within the granitic base overlain by Quaternary sediments. The classification of drill hole geothermal waters have been made in accordance with their δ D and δ^18O values and chloride contents. The “oxygen shift” of the thermal waters seems to be 2‰, due to isotopic exchange reactions between geothermal waters and reservoir展开更多
The coal seams in the Permian Taiyuan Formation and the Carboniferous Shanxi Formation are the primary reservoirs for the coalbed methane （CBM） in the Hancheng region in the Ordos Basin. In this paper, the origin an...The coal seams in the Permian Taiyuan Formation and the Carboniferous Shanxi Formation are the primary reservoirs for the coalbed methane （CBM） in the Hancheng region in the Ordos Basin. In this paper, the origin and evolution of waters associated with CBM production were studied on the basis of water chemistry and isotopes including the chloride and iodine compositions, oxygen and hydrogen stable isotopes, and radioactive isotope ratio of ^129I/^127I. The ratio of ^129I/^127I of water was determined by accelerator mass spectrometry （AMS）. The result shows that the formation water is of NaHCO3 and NaCl types with the total dissolved solids （TDS） varying from 1532.29 mg/L to 7061.12 mg/L. The values of ^129I and I/CI ratio indicate that the formation waters were diluted by meteoric water. The ^129I/^127I ratios range from 6.6×10^-13 to 1459.5~10-13. The ^129I/^127I ratios for most of the samples are between the ^129I/^127I initial value and that of recent anthropogenic water. This age of the formation water samples, obtained through the ^129I decay curve method, ranges from 0 Ma to 18.5 Ma, suggesting that the waters from the Taiyuan Formation and the Shanxi Formation are very young. Two different origins of water are identified in the Hancheng region. One group is dominated by pre-anthropogenic meteoric water, and is characterized by ^129I/^127I ratios lower than the initial value of 15×10^-13 and δD, δ^18O values of waters below the Global Meteoric Water Line. The other group is characterized by ^129I/^127I ratios in excess of 15×10^-13, which has undergone variable degrees of dilution by recent anthropogenic water.展开更多
文摘Isotopic data on drill hole water and surface water samples from the Yengbajain geothermal area as well as an ice sample from the glacial amphitheater in the Mt. Nyainqintanglha to the northwest of the Yangbajain basin are presented in this paper. In consideration of isotopic fractionation during steam separation, the hydrogen and oxygen isotopic ratios for thermal waters collected at the mouths of drill holes have been calibrated. The D/H ratio of thermal waters is similar to that of local precipitation, indicating their meteoric origin. The δ D and δ^18O values of the thermal waters of --150--160 and -17-20‰, respectively are the lowest among those well-known geothermal fields in the world.The recharge area of the geothermal system is at elevation of about 4,800--5,000 m. Drill holes along the axis of a tongueshaped zone where loose Quaternary sediments have been cemented by siliceous material show greater δ D and δ^18O values and discharge tritiumfree thermal waters. It is suggested that the thermal waters may be derived from superhcated water and steam which find their way upwards along the tectonic fractures within the granitic base overlain by Quaternary sediments. The classification of drill hole geothermal waters have been made in accordance with their δ D and δ^18O values and chloride contents. The “oxygen shift” of the thermal waters seems to be 2‰, due to isotopic exchange reactions between geothermal waters and reservoir
基金supported by National Basic Research Program of China(Grant No.2009CB219601)
文摘The coal seams in the Permian Taiyuan Formation and the Carboniferous Shanxi Formation are the primary reservoirs for the coalbed methane （CBM） in the Hancheng region in the Ordos Basin. In this paper, the origin and evolution of waters associated with CBM production were studied on the basis of water chemistry and isotopes including the chloride and iodine compositions, oxygen and hydrogen stable isotopes, and radioactive isotope ratio of ^129I/^127I. The ratio of ^129I/^127I of water was determined by accelerator mass spectrometry （AMS）. The result shows that the formation water is of NaHCO3 and NaCl types with the total dissolved solids （TDS） varying from 1532.29 mg/L to 7061.12 mg/L. The values of ^129I and I/CI ratio indicate that the formation waters were diluted by meteoric water. The ^129I/^127I ratios range from 6.6×10^-13 to 1459.5~10-13. The ^129I/^127I ratios for most of the samples are between the ^129I/^127I initial value and that of recent anthropogenic water. This age of the formation water samples, obtained through the ^129I decay curve method, ranges from 0 Ma to 18.5 Ma, suggesting that the waters from the Taiyuan Formation and the Shanxi Formation are very young. Two different origins of water are identified in the Hancheng region. One group is dominated by pre-anthropogenic meteoric water, and is characterized by ^129I/^127I ratios lower than the initial value of 15×10^-13 and δD, δ^18O values of waters below the Global Meteoric Water Line. The other group is characterized by ^129I/^127I ratios in excess of 15×10^-13, which has undergone variable degrees of dilution by recent anthropogenic water.
