| 水－岩反应的铀系不平衡判别 |
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| 引用本文： | 罗兴章,闵茂中.水－岩反应的铀系不平衡判别[J].地球科学,1998,23(5):537-541. |
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| 作者姓名： | 罗兴章 闵茂中 |
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| 作者单位： | 南京大学地球科学系 |
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| 基金项目： | 国家自然科学基金,中国高放废物深地质处置计划（SDC）基金 |
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| 摘 要： | 天然体系中水－岩反应的铀系不平衡判别，是基于水－岩反应使岩石中天然铀衰变系子体核素＾２３４Ｕ，＾２２６Ｒｂ和六价铀的选择性溶失，造成原始放射性平衡遭到不同程度破坏，因而可利用现今测得的岩石中３组核素放射性活度比值Ａ（＾２３４Ｕ）／Ａ（＾２３８Ｕ），Ａ（＾２３０Ｔｈ）／Ａ（＾２３４Ｕ）和Ａ（＾２２６Ｒａ）／Ａ（＾２３０Ｔｈ）反演判别该岩石曾经历了近代水－岩反应的大致强度和出现，持续时间，这是近十余年
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| 关 键 词： | 水－岩反应 放射性核素 铀系不平衡 铀矿床 成矿 |
JUDGEMENT ON WATER_ROCK INTERACTION IN CRYSTALLINE ROCKS USING URANIUM_SERIES DISEQUILIBRIUM |
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| Luo Xingzhang,Min Maozhong.JUDGEMENT ON WATER_ROCK INTERACTION IN CRYSTALLINE ROCKS USING URANIUM_SERIES DISEQUILIBRIUM[J].Earth Science-Journal of China University of Geosciences,1998,23(5):537-541. |
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| Authors: | Luo Xingzhang Min Maozhong |
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| Abstract: | This paper briefly reviews a new effective method of judgement on water_rock interaction in crystalline rocks using uranium_series disequilibrium. The nuclides 238 U- 234 U- 230 Th attain radioactive secular equilibrium after 1.7Ma, and the respective activity ratios of A ( 234 U)/ A ( 238 U), A ( 230 Th)/ A ( 234 U) and A ( 230 Th)/ A ( 238 U) are all in equal unity in closed geological systems. If the systems are exposed to weathering and groundwater circulation, the preferential mobility of isotopes such as 234 U, 226 Ra and U 6+ allows them to be mobilized selectively, and chemical fraction results in isotopic disequilibria, yielding activity ratio unequal to unity. The resulting disequilibria indicate the action over last 1.5Ma, 350ka, and 8ka respectively. The degrees and time_scales of last water_rock interactions can be evaluated using the three determined parent_daughter activity ratios. The uranium_series disequlibrium method was used in a selective uranium deposit to evaluate the time and degree of water_rock interaction. The deposit has been an access to assessment of the validation of nature analog concept in radio_waste disposal. |
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| Keywords: | water_rock interaction radionuclide uranium_series disequilibrium |
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