极地研究

极地研究 ›› 2013, Vol. 25 ›› Issue (4): 403-413.DOI: 10.3724/SP.J.1084.2013.00403

• 研究论文 • 上一篇    下一篇

东乌旗中铁陨石硅酸盐地球化学特征及对成因的启示

聂喜柯1, 2, 3  孔屏1,2   

  1.  
    1中国科学院地质与地球物理研究所地球深部研究重点实验室，北京 100029；
    2中国科学院地质与地球物理研究所特提斯研究中心，北京 100029；
    3中国科学院大学，北京 100049
  • 收稿日期:2013-03-28 修回日期:2013-07-07 出版日期:2013-12-30 发布日期:2013-12-30
  • 通讯作者: 孔屏
  • 基金资助:

    国家自然科学基金“行星冲击产生的高温高压相变反应：月球火星陨石中后成合晶的研究”

GEOCHEMISTRY OF SILICATES IN THE DONG UJIMQIN QI MESOSIDERITE AND THE IMPLICATIONS FOR ITS ORIGIN

Nie Xike 1, 2, 3, Kong Ping1, 2   

  1.  
    1Key Laboratory of the Earth’s Deep Structure and Process, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;
    2Division of Tethys Research Center, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China;
    3University of the Chinese Academy of Sciences, Beijing 100049, China
  • Received:2013-03-28 Revised:2013-07-07 Online:2013-12-30 Published:2013-12-30

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摘要： 东乌旗中铁陨石为1995年在内蒙发现的、为数不多的降落型中铁陨石，由金属—硫化物和硅酸盐相紧密混合而成。硅酸盐相由角砾部分（主要为角砾状橄榄石和辉长岩岩屑）和非角砾部分组成。岩相学特征、主量元素成分及REE地球化学特征表明角砾状橄榄石、非角砾橄榄石和辉长质硅酸盐（辉长岩岩屑和除橄榄石外的非角砾部分）三者可能分别结晶自不同的岩浆源区。进一步的分析表明Mg含量非常高的角砾状橄榄石可能来自一个分异小行星的橄榄岩质地幔，非角砾橄榄石和辉长质硅酸盐可能和HED陨石具有相同的母体Vesta小行星。冲击碰撞导致两个小行星的物质发生了混合。冲击作用产生的高温（约1200℃—1450℃）使得被撞击小行星表壳玄武质和辉长质岩石发生混合重熔，熔体结晶后形成中铁陨石的辉长质硅酸盐。该温度下非角砾橄榄石和角砾状橄榄石均未发生重熔。该模型较好地解释了角砾状橄榄石、非角砾橄榄石和辉长质硅酸盐三者之间的不平衡现象。

关键词: 东乌旗中铁陨石, 橄榄石, 辉长质硅酸盐, 不平衡, 成因

Abstract: The Dong Ujimqin Qi meteorite is a rare mesosiderite falling in Inner Mongolia, China in 1995. It consists of intimately mixed metal–sulfide and silicates. Silicates in the mesosiderite are composed of clasts (mainly olivine clasts and gabbro clasts) and gabbroic matrix. Petrographic and REE characteristics and major element compositions show that olivine clasts, matrix olivine and gabbroic rocks (including gabbro clasts and gabbroic matrix) may have crystallized from different magmas. Olivine clasts, with high contents of Mg, may be derived from the dunite mantle of a differentiated asteroid, whereas matrix olivine and gabbroic rocks may be from the same parental asteroid, i.e. the Vesta asteroid. An impact event led to mixture of materials from these two asteroids. During the bombardment, temperature rose to 1200—1450℃. Target basaltic and gabbroic rocks from the Vesta melted at the high temperature. Gabbroic rocks in the Dong Ujimqin Qi mesosiderite crystallized from the mixed melt. Olivine (both olivine clasts and matrix olivine), however, did not melt because the temperature was below their melting points. This model explains the disequilibrium between olivine clasts, matrix olivine and gabbroic rocks.

Key words: Dong Ujimqin Qi mesosiderite, olivine, gabbroic rocks, disequilibrium, origin