| 原地生成宇宙成因核素测年技术思考(二):持续抬升区单样品直接计算抬升速率方法 |
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| 引用本文： | 黄费新,李岩,李广伟,董国成,程杨,赵亮亮.原地生成宇宙成因核素测年技术思考(二):持续抬升区单样品直接计算抬升速率方法[J].地质与勘探,2019,55(3):818-825. |
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| 作者姓名： | 黄费新 李岩 李广伟 董国成 程杨 赵亮亮 |
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| 作者单位： | 中国冶金地质总局矿产资源研究院,北京,101300;南京大学地球科学与工程学院,江苏南京,210023;中国科学院地球环境研究所,陕西西安 710061;西安加速质谱中心,陕西西安 710061 |
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| 基金项目： | 国家自然科学基金面上项目（编号：41873064、41176166）资助 |
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| 摘 要： | 原地生成宇宙成因核素测年技术在计算暴露年龄和侵蚀速率时，一直默认样品所在位置不随时间发生高程变化，从而核素生成速率不因高程变化而改变。在构造稳定区，这样的假设是合理的。在构造活动区，往往会因构造运动，地表样品高程发生改变。大冰盖地区（如南极）的冰川消融或加厚也会引起地壳均衡反弹，从而导致样品高程变化，而核素的生成速率将随高程变化而改变。本文对连续抬升情况下，地表样品中宇宙成因核素浓度与生成速率加速率间的计算关系进行了三种方法的数学推导，并提出如何利用单块样品中两种宇宙成因核素（以10Be和26Al为例）浓度计算地表抬升速率，最后指出已往利用宇宙成因核素方法对构造活动区的侵蚀速率的计算存在高估。本文首次提出利用地表在接近稳态侵蚀状态下的单块样品的两种宇宙成因核素直接计算地表持续抬升速率的方法，从而将原地生成宇宙成因核素方法和构造运动学研究直接联系起来。
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| 关 键 词： | 抬升区 原地生成宇宙成因核素 抬升速率 侵蚀速率 |
| 收稿时间： | 2019/1/7 0:00:00 |
| 修稿时间： | 2019/4/2 0:00:00 |
Consideration on the in situ produced cosmogenic nuclide dating technique (2): Direct calculation of surface uplift rates by a single sample |
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| Huang Feixin.Consideration on the in situ produced cosmogenic nuclide dating technique (2): Direct calculation of surface uplift rates by a single sample[J].Geology and Prospecting,2019,55(3):818-825. |
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| Authors: | Huang Feixin |
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| Institution: | Research Institute of Mineral Resources, China Metallurgical Geology Bureau, Beijing; School of Geosciences and Engineering, Nanjing, Jiangsu; Institute of Geoenvironments, Chinese Academy of Sciences, Xi''an, Shaanxi; Xi''an Accelerated Mass Spectrometry Center, Xi''an, Shaanxi |
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| Abstract: | In situ cosmogenic isotopes (e.g., 10Be, 26Al, and 36Cl, 21Ne) have been widely applied to research of geomorphologic evolution to constrain the exposure and erosion history of the earth surface. Generally, the elevation of samples is assumed invariable, thus the production rate of cosmogenic nuclides does not change with the elevation. This assumption is reasonable in tectonically stable areas. Whereas, production rates of cosmogenic nuclides can vary with elevation in the tectonically active regions. Besdies, in areas with great ice sheet (e.g., Antarctica), balanced rebound in the earth''s crust caused by melting or thickening glaciers also can make elevation of samples change, leading to variation of the production rate of cosmogenic nuclides. To address this issue, we derive the relationship between nuclide concentration and the mean annual increment of radiogenic nuclide production rate by three mathematical methods and explore how to calculate the uplift rate using a pair of radio-nuclides data (e.g., 10Beand 26Al). Furthermore, we point out the existence of an overestimate of the erosion rate calculated by cosmogenic isotopes in uplift areas. It is the first time to present a method using a pair of cosmogenic nuclides of a single rock sample to calculate the earth surface uplift rate under steady-state erosion directly, thus linking the cosmogenic nuclide method with tectonic motion research. |
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| Keywords: | uplift areas in situ cosmogenic nuclide erosion rate uplift rate |
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