Zirconium produces cosmogenic Kr through spallation reactions with cosmic rays. Meteoritic zircons (ZrSiO₄) therefore possibly contain a significant amount of cosmogenic Kr in addition to other cosmogenic nuclides. Detection of cosmogenic nuclides from meteoritic zircons would make it possible to determine precise cosmic ray exposure (CRE) ages without knowing the whole rock chemistry because of the robust nature of zircons and limited target elements that produce cosmogenic nuclides in a zircon crystal. Herein, we report the noble gas compositions of zircons separated from the Estherville mesosiderite in addition to those of the silicate and metal parts. The zircons contain cosmogenic noble gas nuclides, and more importantly, cosmogenic ⁸¹Kr (t_1/2 = 2.29 × 10⁵ years) was successfully detected in the zircons. The ⁸¹Kr-Kr exposure age of the zircons was calculated to be 76 ± 5 million years (Ma). This age corresponds to the CRE ages obtained from cosmogenic ³He and ²¹Ne (82 ± 8 and 88 ± 9 Ma, respectively) of the silicate part and the previously reported ³⁶Cl-³⁶Ar age of the metal part (77 ± 9 Ma). The consistent CRE ages using different dating methods demonstrate that the ⁸¹Kr-Kr dating using meteoritic zircons is a new promising tool for determining the CRE age of meteorites. Moreover, based on the ⁸¹Kr-Kr age of the zircons, the production rates of cosmogenic ³He and ²¹Ne in a meteoritic zircon were estimated to be (15 ± 2) × 10⁻⁹ and (0.69 ± 0.04) × 10⁻⁹ cm³ STP g⁻¹ Ma⁻¹, respectively.

中文翻译：

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埃斯特维尔中铁矿锆石中的宇宙成因惰性气体核素

锆通过与宇宙射线的散裂反应产生宇宙成因 Kr。因此，陨石锆石 (ZrSiO ₄ ) 除了其他宇宙成因核素外，可能还含有大量宇宙成因 Kr。从陨石锆石中检测宇宙成因核素将使在不了解整个岩石化学的情况下确定精确的宇宙射线暴露 (CRE) 年龄成为可能，因为锆石的稳健性质和在锆石晶体中产生宇宙成因核素的有限目标元素。在此，我们报告了从埃斯特维尔中铁矿中分离出的锆石的惰性气体成分以及硅酸盐和金属部分的稀有气体成分。锆石包含宇宙性惰性气体核素，更重要的是，宇宙性⁸¹ Kr ( t _1/2 = 2.29 × 10 ⁵  years) 在锆石中被成功检测到。锆石的⁸¹ Kr-Kr 暴露年龄计算为 76 ± 5 百万年 (Ma)。该年龄对应于从硅酸盐部分的宇宙成因³ He 和²¹ Ne（分别为 82 ± 8 和 88 ± 9 Ma）和先前报道的金属部分的³⁶ Cl- ³⁶ Ar 年龄（77 ± 9 Ma ）中获得的 CRE 年龄）。使用不同测年方法的一致CRE年龄表明，使用陨石锆石的⁸¹ Kr-Kr定年是确定陨石CRE年龄的新工具。此外，根据锆石的⁸¹ Kr-Kr 年龄，宇宙成因的产率陨石锆石中的³ He 和²¹ Ne 估计分别为 (15 ± 2) × 10 ^-9和 (0.69 ± 0.04) × 10 ^-9  cm ³ STP g ^-1  Ma ^-1。