首页 | 学报简介 | 编委会 | 投稿指南 | 订阅指南 | 文件下载 | 期刊浏览 | 关键词检索 | 高级检索 | 联系我们   
戴德求,包海梅,刘爽,尹锋. 2020. Kainsaz (CO3)陨石中两个富Al球粒的氧同位素组成特征与形成演化. 岩石学报, 36(6): 1850-1856
Kainsaz (CO3)陨石中两个富Al球粒的氧同位素组成特征与形成演化
作者单位
戴德求 湖南科技大学地质研究所, 湘潭 411201 
包海梅 湖南科技大学地质研究所, 湘潭 411201
中国科学院地球化学研究所, 贵阳 550081 
刘爽 湖南科技大学地质研究所, 湘潭 411201
中国科学院地球化学研究所, 贵阳 550081 
尹锋 湖南科技大学地质研究所, 湘潭 411201
湖南科技大学页岩气资源利用湖南省重点实验室, 湘潭 411201 
基金项目:本文受国家自然科学基金项目(41673070)和湖南省教育厅重点科研项目(18A204)联合资助.
摘要:
      富Al球粒是原始球粒陨石中一种矿物岩石学特征介于富钙铝包体(CAIs)和镁铁质硅酸盐球粒之间的特殊集合体,所以常常认为富Al球粒在认识CAIs和镁铁质硅酸盐球粒形成演化过程中的相互联系具有特殊意义。然而,对富Al球粒的初始物质组成以及形成演化过程一直存在较多争议,而氧同位素组成研究能够对球粒演化和早期星云环境等提供重要的信息。在本文中,我们报导了来自Kainsaz (1937年降落于俄罗斯,CO3型)碳质球粒陨石中的2个富Al球粒(编号K1-CH1和K2-CH2)的矿物岩石学和氧同位素组成特征。K1-CH1的矿物组成主要为橄榄石、低钙辉石和富钙长石,K2-CH2为橄榄石和富钙长石。2个球粒中的矿物均具有贫16O同位素组成特征。K1-CH1中矿物的Δ17O组成基本上位于2个区间:-11.1‰~-8.7‰和-3.9‰~0.4‰;而K2-CH2的Δ17O介于-6.6‰~-0.6 ‰之间,且具有从中部至边部升高的趋势。矿物岩石学和氧同位素特征表明,这2个富Al球粒的初始物质组成为富CAIs和镁铁质硅酸盐。在球粒熔融结晶过程中,与贫16O同位素组成(Δ17O:-8.7‰~-7.8‰)的星云发生了氧同位素交换。球粒形成后,发生迁移进入陨石母体,在相对更贫16O同位素组成(Δ17O:-0.6‰~0.4‰)的母体中(流体参与)发生变质作用,并再次发生了氧同位素交换。
英文摘要:
      Aluminum-rich chondrules are one of the most interesting components of primitive chondrites, because they have characteristics in petrography and mineralogy that are similar to both Ca- and Al-rich inclusions (CAIs) and ferromagnesian chondrules. However, their precursor and formation history remain poorly constrained, especially with respect to their oxygen isotopic distributions. In this study, we report on the petrography, mineral chemistry, and oxygen isotope ratios of two Al-rich chondrules (K1-CH1 and K2-CH2) in the Kainsaz (CO3) carbonaceous chondrites. The major phases in K1-CH1 are plagioclase, olivine and Ca-poor pyroxene, and those in K2-CH2 are plagioclase and olivine. All minerals in two Al-rich chondrules are 16O-poor. The Δ17O values in K1-CH1 vary in two ranges of from -11.1‰ to -8.7‰ and from -3.9‰ to 0.4‰, while those in K2-CH2 vary from -6.6‰ to -0.6‰ with a tendency increasing from the core to rim. These observations provide a strong indication that the two Al-rich chondrules formed by the melting and crystallization of a mixture of materials from CAIs and ferromagnesian chondrules. The precursor materials of K1-CH1 and K2-CH2 are CAIs+olivine-pyroxene-rich chondrules and CAIs+olivine-rich chondrules, respectively. The 16O-poor isotopic compositions of all components in two Al-rich chondrules can be explained by oxygen isotopic exchange between the melt and 16O-poor nebular gas (Δ17O:-8.7‰~-7.8‰) during melting in chondrule-forming regions; whereas the minerals in two chondrules could have experienced further oxygen isotopic exchange with a relatively 16O-poor reservoir (Δ17O: -0.6‰~0.4‰) on the parent body, likely during fluid-assisted thermal metamorphism.
关键词:矿物岩石学特征  氧同位素组成  富Al球粒  初始物质  氧同位素交换
投稿时间:2020-02-17  修订日期:2020-03-16
HTML   查看全文   查看/发表评论    下载PDF阅读器

京ICP备05029136号-23
主办单位:中国科学院地质与地球物理研究所
印刷版(Print): ISSN 1000-0569 网络版(Online): ISSN 2095-8927
单位地址:北京9825信箱/北京朝阳区北土城西路19号
本系统由北京勤云科技发展有限公司设计

手机扫一扫