文章摘要
黄费新.原地生成宇宙成因核素测年技术思考(四): 核素浓度年份化数列累加方法探讨[J].地质与勘探,2020,56(1):182-189
原地生成宇宙成因核素测年技术思考(四): 核素浓度年份化数列累加方法探讨
Consideration on in situ produced cosmogenic nuclide dating techniques (4):Discussion on the accumulation method of nuclide concentration annualized data
投稿时间:2019-03-25  修订日期:2019-10-23
DOI:10.12134/j.dzykt.2020.01.018
中文关键词: 原地生成 宇宙成因核素 浓度年份分解 计算等式 侵蚀速率
英文关键词: in situ, cosmogenic nuclide, annual decomposition of concentration, calculation equation, erosion rate
基金项目:国家自然科学基金面上项目(编号:41873064、41176166)资助
作者单位E-mail
黄费新 中国冶金地质总局矿产资源研究院北京 南京大学地球科学与工程学院江苏南京中国科学院地球环境研究所陕西西安 西安加速质谱中心陕西西安 liyan@cmgb.com 
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中文摘要:
      原地生成宇宙成因核素测年技术中,计算核素浓度的传统通用等式,假设了地表侵蚀速率(参数ε)及样品的位置在暴露期间保持不变,从而简化了计算过程。然而这种假设可能并不符合复杂地质背景的实际情况,从而造成计算结果误差较大,与其他测年方法结果也难以相互比较和匹配。本文利用将核素总浓度按年份分解为每年生成的浓度,经衰变和侵蚀的综合影响后至今剩余的浓度(称为年份净剩余浓度),组成数列累加的办法,分别推导了地表样品在高程以及侵蚀速率变化情况下的核素浓度计算等式。在此基础上,给出了地表生成速率和侵蚀速率逐年变化情况下的通用浓度年份化累加等式。最后讨论了传统浓度计算等式中的参数ε(侵蚀速率)的地质意义,明确了ε是一个积分中值,并不代表暴露期间的算术平均侵蚀速率,而是每年的侵蚀速率以自然指数加权的复杂方式(即T年前的那一年的生成浓度将乘以e^(-(λ+ρε/Λ)(T-1) ))影响到样品的最终浓度值。
英文摘要:
      It is assumed that the surface erosion rate(ε)and the position of the sample are constant during exposure in traditional formula of in-situ cosmogenic nuclide dating technology, thus calculation is simplified. However, such a hypothesis may be inconsistent with the background of complex geology, so resulting in big errors and cannot be compared with dating results of other methods. To solve this problem, this work decomposes the total concentration of nuclides into the concentration generated each year and the remaining concentration by decay and erosion(called net residual concentration for the year), then these data are accumulated into a sequence. Equations of nuclide concentration under the change of sample elevation and erosion rate are derived, respectively. The accumulation equation of the concentration is given on the condition surface production rate and erosion rate varying each year. The geological meaning of the parameter ε (erosion rate) in the traditional concentration formula is discussed. It is clarified that the erosion rate for a given year affects the final concentration of the sample in a complex way by natural exponential weighting (the annual concentration of T years ago is multiplied by the
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