In the present work, uranium concentrations were measured in twenty surface soil samples forselected regions in AI-Anbargovernorate using fission track etch technique, CR-39 track detector was used for registration of...In the present work, uranium concentrations were measured in twenty surface soil samples forselected regions in AI-Anbargovernorate using fission track etch technique, CR-39 track detector was used for registration of induced fission tracks. The results show that, the uranium concentrations ranged from 4.61 ppm, 56.93 Bq/kg （AL-Falluja AL-Jolan District） to 1.81 ppm 22.35 Bq/kg （Anah）with an average 3.42±0.79 ppm, 41.76±9.04 Bq/kg. The present results have shown that the uranium concentrations in the studied surface soil samples were less than the allowed limit 11.7 ppm recommended by UNSCEAR, 1993.展开更多
In this study uranium and thorium contents and depositional characteristics of ay rhan bituminous shales（ BS）, west of Ankara（central Anatolia）, are investigated. Samples used were collected from boreholes opened ...In this study uranium and thorium contents and depositional characteristics of ay rhan bituminous shales（ BS）, west of Ankara（central Anatolia）, are investigated. Samples used were collected from boreholes opened by Park Holding Ltd. A total of 25 samples were taken from bituminous shale levels in boreholes drilled at 6 different locations in the study area. The H rka formation which hosts bituminous shale deposits is a volcanosedimentary sequence and all lithofacies indicate that a lacustrine environment where the water level was continuously changed. In addition to hydrocarbon generation potential, bituminous shales also accumulate significant amount of radioactive elements such as uranium and thorium. The average uranium and thorium concentrations of BS（1.83/2.62 ppm） are much lower than averages of UC, NASK and PAAS（uranium： 2.70/2.66/3.10 ppm; thorium： 8.50/12.30/14.60 ppm）. Low uranium contents in comparison to those of similar lacustrine environments might be attributed to that waters of depositional environment of BS contain low concentration of dissolved uranium and redox conditions were of oxic and dioxic character. Correlation data indicate that U and Th have a similar source and are associated predominantly with clays and phosphates and dominantly with organic material. Radioactive elements in the basin might be derived from Paleozoic granites and metamorphites（e.g. gneiss, schist） which comprise the basement and volcanism which was active in the region throughout the Miocene period. These elements are probably associated with uraniferous phosphate minerals（e.g. autunite, torbernite） which occur in granite, gneiss and schist. BS with average TOC content of 10.96 % shows very good/perfect source rock potential. Positive correlations between Gamma-Ray values and U, Th and K concentrations imply that radioactivity might be originated from these three elements.展开更多
The apatite(U-Th)/He tbermochronometry has been used to study the tectono-thermal evolution of mountains and sedimentary basins for over ten years.The closure temperature of helium is important for the apatite(U-Th)/H...The apatite(U-Th)/He tbermochronometry has been used to study the tectono-thermal evolution of mountains and sedimentary basins for over ten years.The closure temperature of helium is important for the apatite(U-Th)/He thermochronometry and has been widely studied by thermal simulation experiments.In this paper,the apatite He closure temperature was studied by estab-lishing the evolutionary pattern between apatite He ages and apatite burial depth based on examined apatite He ages of natural samples obtained from drillholes in the Tarim basin,China.The study showed that the apatite He closure temperature of natural samples in the Tarim basin is approximately 88+5~C,higher than the result(~75℃)obtained from the thermal simulation exper-iments.The high He closure temperature resulted from high effective uranium concentration,long-term radiation damage accu-mulation,and sufficient particle radii.This study is a reevaluation of the conventional apatite He closure temperature and has a great significance in studying the uplifting events in the late period of the basin-mountain tectonic evolution,of which the uplift-ing time and rates can be determined accurately.展开更多
文摘In the present work, uranium concentrations were measured in twenty surface soil samples forselected regions in AI-Anbargovernorate using fission track etch technique, CR-39 track detector was used for registration of induced fission tracks. The results show that, the uranium concentrations ranged from 4.61 ppm, 56.93 Bq/kg （AL-Falluja AL-Jolan District） to 1.81 ppm 22.35 Bq/kg （Anah）with an average 3.42±0.79 ppm, 41.76±9.04 Bq/kg. The present results have shown that the uranium concentrations in the studied surface soil samples were less than the allowed limit 11.7 ppm recommended by UNSCEAR, 1993.
基金supported by Ankara University Scientific Research Projects Coordination Unit(Project No:09B4343013)
文摘In this study uranium and thorium contents and depositional characteristics of ay rhan bituminous shales（ BS）, west of Ankara（central Anatolia）, are investigated. Samples used were collected from boreholes opened by Park Holding Ltd. A total of 25 samples were taken from bituminous shale levels in boreholes drilled at 6 different locations in the study area. The H rka formation which hosts bituminous shale deposits is a volcanosedimentary sequence and all lithofacies indicate that a lacustrine environment where the water level was continuously changed. In addition to hydrocarbon generation potential, bituminous shales also accumulate significant amount of radioactive elements such as uranium and thorium. The average uranium and thorium concentrations of BS（1.83/2.62 ppm） are much lower than averages of UC, NASK and PAAS（uranium： 2.70/2.66/3.10 ppm; thorium： 8.50/12.30/14.60 ppm）. Low uranium contents in comparison to those of similar lacustrine environments might be attributed to that waters of depositional environment of BS contain low concentration of dissolved uranium and redox conditions were of oxic and dioxic character. Correlation data indicate that U and Th have a similar source and are associated predominantly with clays and phosphates and dominantly with organic material. Radioactive elements in the basin might be derived from Paleozoic granites and metamorphites（e.g. gneiss, schist） which comprise the basement and volcanism which was active in the region throughout the Miocene period. These elements are probably associated with uraniferous phosphate minerals（e.g. autunite, torbernite） which occur in granite, gneiss and schist. BS with average TOC content of 10.96 % shows very good/perfect source rock potential. Positive correlations between Gamma-Ray values and U, Th and K concentrations imply that radioactivity might be originated from these three elements.
基金supported by the National Natural Science Foundation of China(41125010 and 41072103)the National Basic Research Program of China(2011CB201101)
文摘The apatite(U-Th)/He tbermochronometry has been used to study the tectono-thermal evolution of mountains and sedimentary basins for over ten years.The closure temperature of helium is important for the apatite(U-Th)/He thermochronometry and has been widely studied by thermal simulation experiments.In this paper,the apatite He closure temperature was studied by estab-lishing the evolutionary pattern between apatite He ages and apatite burial depth based on examined apatite He ages of natural samples obtained from drillholes in the Tarim basin,China.The study showed that the apatite He closure temperature of natural samples in the Tarim basin is approximately 88+5~C,higher than the result(~75℃)obtained from the thermal simulation exper-iments.The high He closure temperature resulted from high effective uranium concentration,long-term radiation damage accu-mulation,and sufficient particle radii.This study is a reevaluation of the conventional apatite He closure temperature and has a great significance in studying the uplifting events in the late period of the basin-mountain tectonic evolution,of which the uplift-ing time and rates can be determined accurately.
