摘要
宁强碳质球粒陨石的球粒和基质中出现大量圆形的不透明矿物集合体。其中的主要矿物为磁铁矿、富镍金属和硫化物,另有少量磷酸盐、硅酸盐及微量的铂族金属。离子探针测定显示:①磁铁矿的氧同位素组成服从质量分馏[斜率为0.51±0.04,△^17O为(-2.8±0.4)‰],δ^18O值在-15.3‰~-1.6‰的较大范围内变化;②球粒中的橄榄石(△^17O为-5.0‰)与不透明矿物集合体处于氧同位素不平衡状态。不透明矿物集合体是由小行星母体中的蚀变反应产生的,金属铁被氧化为磁铁矿,同时使剩余的金属富集镍。
Chondrules and matrix of the Ningqiang carbonaceous chondrite contain abundant opaque assemblages (OAs). They are composed of magnetite, Ni-rich metals and Fe-sulfides, with minor phosphate, silicate, and trace amounts of platinum-group element metals. The ion probe measurements show that : ①The O-isotopic compositions of magnetite fall on a mass-dependent fractionation line (slope: 0.51 ± 0.04, △^17O: - 2.8 ± 0.4‰), and δ^18O values range widely from - 15.3 ‰ to - 1.6 ‰. ② The OAs and cbondrules (△^17O of the olivine: - 5.0‰) are unequilibrated with regard to their O-isotopic compositions. OAs most likely formed by secondary alteration processes in a parent body, where aqueous fluid oxidized the metal into magnetite and enriched the residual metal in Ni.
出处
《地球学报》
EI
CAS
CSCD
北大核心
2005年第B09期6-9,共4页
Acta Geoscientica Sinica
基金
本文为中国科学院百人计划“引进国外杰出人才”资助项目.