陨石和一些天体表面如果长期暴露在太空中受到宇宙射线的辐射作用会使其同位素组成发生改变。后果之一就是会影响到一些短半衰期同位素定年的准确性， 因为同位素组成上的变化有可能部分反映了辐射效应而非放射性衰变。目前针对铁族元素的辐射效应的研究比较少。这些元素主要是通过陨石中的靶元素Fe、Ni与宇宙射线作用发生裂变反应生成的。在这个项目中申请人拟以Cr同位素为手段对辐射效应对铁陨石中铁族元素同位素组成的影响进行系统的研究。我们将系统研究暴露年龄、化学成分（特别是Fe/Ni比值），以及与辐射表面的距离等因素对宇宙射线辐射作用的影响。在这个基础上建立定量校正辐射影响的模型。 最后结合这个模型对angrite的53Mn-53Cr体系进行再研究，进而为太阳系53Mn的初始丰度提供新的制约。

Long exposure to galactic cosmic ray (GCR) irradiation can affect the isotopic compositions of meteorites and planetary surfaces. One of the consequences is that it will affect the use of short-lived nuclide chronometers, as part of the isotopic variations may be not caused by radioactivity. For a long time the GCR effects on iron group elements have been understudied. GCRs alter the isotopic composition of these elements through spallation reactions on target elements such as Fe and Ni. Here we propose to use Cr isotopes to study the GCR effects in iron meteorites. We plan to systematically study the constribution of various factors: exposure age, chemical composition, distance from the exposure surface, on GCR effects. We also plan to come up with a model for quantitative correction of GCR effects on Cr isotopic composition of meteorites. Finally we will incorporate this model to re-visit the Mn-Cr systematics of angrites to further constrain the initial 53Mn distribution in the solar system.