| 宁强陨石中不透明矿物集合体的氧同位素和成因研究 |
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| 引用本文：王英,徐伟彪,华欣,管云彬.2005.宁强陨石中不透明矿物集合体的氧同位素和成因研究[J].地球学报,26(z1):6-9. |
| DOI：10.3975/cagsb.2005.s1.03 |
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| 基金项目:本文为中国科学院百人计划“引进国外杰出人才”资助项目 |
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| 中文摘要: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,Δ17O为（-2.8±0.4)‰],δ18O值在-15.3‰~-1.6‰的较大范围内变化；②球粒中的橄榄石(Δ17O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。 |
| 中文关键词:不透明矿物集合体 氧同位素 离子探针微区分析 宁强碳质球粒陨石 |
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| Oxygen Isotopes and Origin of Opaque Assemblages in Ningqiang Carbonaceous Chondrites |
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| Abstract: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 (slop：0.51±0.04, Δ17O：-2.8±0.4‰), and δ18O values range widely from -15.3‰ to-1.6‰. ②The OAs and chondrules (Δ17O 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. |
| keywords:opaque assemblage O-isotope in situ ion microprobe analysis Ningqiang carbonacecus chondrite |
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