摘要
对69个普通球粒陨石进行了岩石学及化学组成的研究,在此基础上提出橄榄石成分(mol％Fa)-铁纹石中钴含量两维分类参数,69个球粒陨石包括25个H、20个L、17个LL、2个介于H与L之间及5个介于L与LL之间的类型。根据矿物学的分类参数及化学组成的研究,普通球粒陨石母体至少有5个,即H、H/L、L、L/LL及LL,而不是3个(H、L及LL)。每群球粒陨石的不同岩石类型之间化学成分无重大的变化,表明球粒陨石的变质作用是在封闭体系的条件下发生的。本文给出了普通球粒陨石不同化学群和不同岩石类型的平均化学成分。
Described in this paper are the petrology and chemistry of 69 ordinary chondrites (23 from China).Thin sections of each chondrite were examined microscopically in transmitted and reflected light. The compositions of olivine and kamacite were determined by electron microprobe. On the plot of the Co concentration of kamacite vs. the Fa content of olivine there is a hiatus between H and L, but no hiatus between L and LL. Five chondrites and two chondrites fall respectively between the main L and LL, and between the main H and L clusters- So we have the olivine (mol% Fa)-kamacite Co concentration (mg/g) taxonomic parameter for classifying ordinary chondrites. The concentrations of 26 elements were determined by replicate neutronactivation analysis in 69 ordinary chondrites (25 H, 20 L, 17 LL, 2H/L and 5L/LL), and the mean chemical compositions of different groups and different petrographic types have been obtained.With the exception of highly volatile Br, no significant differences in abundances are observed among the petrographic types of each group. The absence of a relationship between composition and petrographic type is consistent with the models requiring progressive thermal metamorphism of primitive unequilibrated materials and sequential accretion of nebular materials. Variations in oxidation state among ordinary chondrites are reflected by some mineralo-gical and chemical properties.
出处
《地球化学》
CAS
CSCD
北大核心
1991年第1期13-26,共14页
Geochimica
基金
国家科学基金(4880161)
