南极格罗夫山陨石的宇宙暴露年龄及40Ar/39Ar年龄研究

Cosmic ray exposure age is the irradiation time that meter scale meteorite began to exposure to and accept cosmic rays irradiation，while the 40Ar/39Ar age reflect the age of cooling below the Ar-closure temperature. Both of them are the basic scientific parameters of meteorite, which play crucial roles in judging paired meteorites, looking for parent body and exploring impact history and thermal history. At present, the studying of age dating methods for cosmic ray exposure is still very limited in China, and most of the published data are obtained from foreign meteorite noble gas laboratory using full fusion method with furnace. However, the traditional full fusion method often requires large amount of samples and can not extract micro-scale information of meteorite. In addition, the traditional full fusion method has not combined with 40Ar/39Ar dating method for different magnetic particles and feldspar in meteorites to explore the thermal history happened on the surface of asteroid parent in China. The project intends to choose the meteorites from Antarctic Grove Mountains as the research object. Through combining methods of laser micro-scale noble gas analysis and step-heating 40Ar/39Ar dating, the exact cosmic ray exposure and 40Ar/39Ar ages of meteorites from Antarctic Grove Mountains would be determined, and the impact history and thermal history of meteorites or parent asteroid could also be explored. The successful implementation of this project would lay a chronology foundation for further exploration of meteorites from Antarctic Grove Mountains and deep space in China.

宇宙暴露年龄是米级大小的陨星开始暴露于宇宙射线并接受其照射的时间，而40Ar/39Ar年龄是矿物在封闭温度下的气体保存年龄，它们均是陨石的基本科学参数，对于判断成对陨石，寻找母体及反演小行星体的撞击历史和热历史具有至关重要的作用。目前，国内对于宇宙暴露年龄测年方法的研究还处于探索阶段，已发表的数据大多在国外稀有气体实验室采用传统高温炉全熔法获得，样品用量大且不能提取微米尺度上的信息，尚未结合陨石中不同磁性颗粒及长石的40Ar/39Ar年龄来探讨小行星母体的热历史。本项目拟以南极格罗夫山陨石为研究对象，通过微量陨石样品的激光微区稀有气体方法和40Ar/39Ar多阶段升温熔融分析手段，从微米尺度测定南极陨石中不同磁性颗粒及单矿物的宇宙暴露年龄和40Ar/39Ar年龄，探讨陨石或母体表面的撞击历史及热历史，为我国的南极陨石探索性的研究工作和深空探测奠定年代学基础。

宇宙暴露年龄是米级大小的陨星开始暴露于宇宙射线并接受其照射的时间，是陨石的基本科学参数，对于判断成对陨石，寻找母体及反演小行星体的撞击历史和热历史具有至关重要的作用。本项目以陨石标样项目以陨石标样Millbillilllie和南极格罗夫山普通球粒陨石为研究对象，成功建立和完善微量陨石激光融样关键技术，并以陨石标样Millbillilllie对方法进行验证，获得了可靠的稀有气体特征和宇宙暴露年龄；系统地研究了南极格罗夫山普通球粒陨石的基本特征，获得五块普通球粒陨石的稀有气体含量和宇宙暴露年龄，探讨其起源和宇宙暴露历史；并拓展磷灰石单颗粒的(U-Th)/He年代学研究，建立相关的定年实验流程。该项目的成果以及所建立的技术，为我国的南极陨石探索性的研究工作和深空探测奠定年代学基础。