铁陨石及中铁陨石的稀有气体同位素丰度和放射性核素活度

Noble gas isotopic abundances and radionuclide activities of iron meteorites and mesosiderites

测定了两个铁陨石及两个中铁陨石的稀有气体同位素丰度和10Be、26Al和36Cl的放射性核素活度。在所研究的4个陨石中，东乌珠穆沁旗(类型Ⅰ)、渭源(类型Ⅲ)中铁陨石及宁波铁陨石(ⅣA)是在中国回收的，另一个无结构铁陨石Rafruti是于1886年在瑞士发现的。根据10Be-21Ne、26Al-21Ne和36Cl-36Ar计算了两个铁陨石的产率及宇宙射线暴露年龄。其中Rafruti无结构铁陨石为(6.9±1.5)Ma，在所有无结构铁陨石中是最低的；宁波铁陨石为(107±15)Ma,落在八面体铁陨石的范围内。东乌珠穆沁旗及渭源中铁陨石的硅酸盐相在主元素丰度上类似于紫苏钙长无球粒陨石，其宇宙射线暴露年龄分别为(252±50)Ma和(25.9±5.0)Ma。

Noble gas isotopic abundances and 10Be, 26Al and 36Cl radionuclide specific activities of two iron meteorites and two mesosiderites were determined. Among the investigated meteorites, Dong Ujimqin Qi (type Ⅰ ), Weiyuan (type Ⅲ ) mesosiderites and Ningbo (type Ⅳ A) iron meteorite were recovered in China, and Rafruti ataxite was found in 1886 in Switzerland. Based on the pair 10Be- 21Ne, 26Al- 21Ne and 36Cl- 36Ar, production rates and cosmic ray exposure ages were calculated. Rafruti ataxite has the youngest exposure age, (6.9± 1.5) Ma, of all ataxites, whereas Ningbo with that of (107± 15) Ma falls within the range of the other ochedrites. Major element abundances of the silicate phase of the two mesosiderites are similar to those of howardites. The cosmic ray exposure ages are (242± 50) Ma for Dong Ujimqin Qi mesosiderite and (25.4± 5.0) Ma for Weiyuan mesosiderite.