原地生成宇宙成因核素暴露和埋藏年龄计算方法的统一  

Unify the exposure and the burial age calculating methods by in situ produced cosmogenic nuclides

作　　者：黄费新 程杨 李岩 李广伟 董国成 梁霞[5] HUANG FeiXin;CHENG Yang;LI Yan;LI GuangWei;DONG GuoCheng;LIANG Xia(Institute of Mineral Resources Research,China Metallurgical Geology Bureau,Beijing 101300,China;School of Earth Sciences and Engineering,Nanjing University,Nanjing 210023,China;Institute of Earth Environment,Chinese Academy of Sciences,Xi'an 710061,China;Xi'an Accelerator Mass Spectrometry Center,Xi'an 710061,China;Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081,China)

机构地区：[1]中国冶金地质总局矿产资源研究院,北京101300 [2]南京大学地球科学与工程学院,南京210023 [3]中国科学院地球环境研究所,西安710061 [4]西安加速质谱中心,西安710061 [5]中国地质科学院地质力学研究所,北京100081

出　　处：《岩石学报》2021年第5期1611-1618,共8页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41873064、41176166)资助。

摘　　要：原地生成宇宙成因核素测年技术计算暴露和埋藏年龄以往分属于不同的计算方法体系,采用的计算等式不同。实际上,无论是暴露过程还是埋藏过程,都涉及了核素的新生和已生成核素的减少,其浓度计算方法原理上有相通之处。考察被研究样品历史上某时点的状态,侵蚀使样品距地表深度不断减小,埋藏使样品距地表深度不断增加,刚好是一种相反的过程,而原地生成宇宙成因核素的生成速率与距地表深度呈指数函数形式相关。本文按照原地生成宇宙成因核素浓度与暴露时间、侵蚀速率间关系的计算原理,推导出在匀速埋藏过程中,计算被测试样品的浓度随时间的变化时,以样品目前生成速率为标准,可将埋藏速率(β)视为负侵蚀速率(-ε),从而将暴露年龄和埋藏年龄的计算等式统一起来。非匀速埋藏情况,通过求导计算,仍可视埋藏为负侵蚀。在埋藏速率和侵蚀速率用同一参数指代,埋藏速率可视为负侵蚀速率的基础上,推导出不同埋藏(侵蚀)模式下样品的核素浓度计算等式。理论上根据不同埋藏(侵蚀)模式,可计算复杂地表演化过程样品的埋藏(暴露)年龄。The exposure and burial ages were calculated using in situ produced cosmogenic nuclides by different methods.In fact,both exposure and burial processes involve production and reduction of cosmogenic nuclides,thus the nuclide concentration calculating methods have similarities in principle.As far as the depth from earth surface of a sample in its exposure or burial history is considered,erosion decreases the depth of the sample,while burial increases the depth,which is just an opposite process.The produce rates of in situ produced cosmogenic nuclides are correlated with the depth from the earth surface in the form of exponential function.According to the calculating principle of the relationship among in situ produced cosmogenic nuclide concentration,exposure time and erosion rate,it is deduced that the constant burial rate(β)can be regarded as negative constant erosion rate(-ε)in calculating the sample concentration variation with time in the process of burial,taking the current produce rate of the sample as the standard.Thus,the equation for calculating exposure age and burial age is unified.In the case of non-uniform burial rate,the burial rate can still be regarded as the negative erosion rate by derivative calculation.On the basis that burial rate and erosion rate are denoted by the same parameter,and the burial rate can be regarded as the negative erosion rate,the calculation equation of nuclide concentration of sample under different burial(erosion)modes is deduced.The burial(exposure)age of samples with complex evolution processes can be calculated according to different burial(erosion)modes theoretically.

关 键 词：宇宙成因核素 暴露年龄 埋藏年龄 计算方法 统一 

分 类 号：P597.3[天文地球—地球化学]