Cosmic-ray exposure histories of two Antarctic meteorites from Chinese collections and the Guangmingshan and Zhuanghe chondrites  

作　　者：王道德 林杨挺 刘小汉 琚宜太 

机构地区：[1]Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China [2]Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China

出　　处：《Science China Earth Sciences》2003年第12期1236-1240,共5页中国科学（地球科学英文版）

基　　金：the National Science Fund for Distinguished Young Scholar(Grant No.40025311); Pilot Project of Knowledge Innovation Program of Chinese Academy of Sciences(Grant No.KZCX2-303-4).

摘　　要：Concentrations of noble gases of two Antarctic meteorites (GRV 98002, 98004) from Chinese collections, and the Guangmingshan and Zhuanghe chondrites were measured. Based on the petrography and mineralogy of these meteorites, and production rates of the cosmogenic nuclides, we calculated cosmic-ray exposure and gas retention ages of the four chondrites. Exposure ages of the four chondrites are 0.052 Ma 0.008 Ma (GRV 98004, H5), 17.0 Ma 2.5 Ma (GRV98002, L5), 3.8 Ma 0.6 Ma (Zhuanghe, H5), and 68.9 Ma 10 Ma (Guangmingshan, H5), respectively. The exposure age of GRV 98004 is the lowest value of Antarctic meteorites reported up to date; while that of Guangmingshan is higher than other Chinese meteorites of H-group. Both GRV 98002 and Zhuanghe have low 4He concentrations, probably due to shock effects or solar heating at orbits with small perihelion distances during cosmic-ray exposure. On the other hand, losses of cosmogenic 3He and 4He are correlated with both GRV 98002 and Guangmingshan.Concentrations of noble gases of two Antarctic meteorites (GRV 98002, 98004) from Chinese collections, and the Guangmingshan and Zhuanghe chondrites were measured. Based on the petrography and mineralogy of these meteorites, and production rates of the cosmogenic nuclides, we calculated cosmic-ray exposure and gas retention ages of the four chondrites. Exposure ages of the four chondrites are 0.052 Ma ± 0.008 Ma (GRV 98004, H5), 17.0 Ma ± 2.5 Ma (GRV98002, L5), 3.8 Ma ± 0.6 Ma (Zhuanghe, H5), and 68.9 Ma ± 10 Ma (Guangmingshan, H5), respectively. The exposure age of GRV 98004 is the lowest value of Antarctic meteorites reported up to date; while that of Guangmingshan is higher than other Chinese meteorites of H-group. Both GRV 98002 and Zhuanghe have low4He concentrations, probably due to shock effects or solar heating at orbits with small perihelion distances during cosmic-ray exposure. On the other hand, losses of cosmogenic3He and4He are correlated with both GRV 98002 and Guangmingshan.

关 键 词：chondrite  NOBLE gas  COSMIC-RAY EXPOSURE age. 

分 类 号：P185[天文地球—天文学]