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西宁陨石的岩石学特征及其类型划分

【标题】西宁陨石的岩石学特征及其类型划分

【Title】PETROLOGIC CHARACTERISTICS AND CLASSIFICATION OF THE XINING METEORITE

【DOI】10.3724/SP.J.1084.2013.00394

【作者】 陈宏毅; 缪秉魁; 刘希军; 谢兰芳; 夏志鹏; 陈丽菲

【Author】 Chen Hongyi ; Miao Bingkui ; Liu Xijun ; Xie Lanfang ; Xia Zhipeng ; Chen Lifei

【期刊】极地研究

【Journal】ADVANCES IN POLAR SCIENCE

【期刊年份】2013

【卷】25

【期】4

【关键词】 西宁陨石; 普通球粒陨石; 平衡型; L5; 降落陨石

【Keywords】 Xining meteorite; Ordinary chondrite; Equilibrated type; L5; Meteorite fall

【摘要】西宁陨石具有典型的球粒结构,球粒轮廓依稀可辨-模糊,基质重结晶程度中-高等,次生斜长石粒度5-40μm,部分颗粒大于50μm。橄榄石和低钙辉石的化学成分均一:球粒中橄榄石Fa24.7-25.2,平均Fa24.9,相对标准偏差PMD值0.64%;低钙辉石Fs21.3-21.9 En 77.6-78.2 Wo 0.46-0.57,平均Fs21.5,Fs的PMD值0.84%。说明该陨石已达热力学平衡状态,为平衡型普通球粒陨石。根据该陨石结构构造特征、金属含量、矿物化学组成特征和热变质特征(平衡温度为778℃),西宁陨石被划分为L群普通球粒陨石,岩石类型为5型,但已开始向6型过渡。该陨石的冲击变质程度为S3,风化程度W0。陨石母体形成之后遭受了冲击变质作用和热变质作用,导致原始球粒破碎、脱玻化和基质重结晶。

【Abstract】 Xining meteorite has a typically chondritic texture. The matrix displays a moderate to high degree of recrystallization, most plagioclase grains are around 5-40μm and a few grains greater than 50μm in diameter . Chemical compositions of olivine and low-Ca pyroxene in Xining meteorite are homogeneous: eg. olivine (Fa 24.7-25.2,avg. Fa 24.9, PMD 0.64%); low-Ca pyroxene ( Fs 21.3-21.9, avg. Fs 21.5, PMD 0.84%; En 77.6-78.2, avg. En 78.6; Wo 0.46-0.57, avg. Wo 0.46). This feature indicates that olivine and low-Ca pyroxene in Xining meteorite are in thermodynamic equilibrium and Xining meteorite should belong to an equilibrated ordinary chondrite. Based on the textural characteristics,metal abundance, chemical composition of silicate minerals and thermal metamorphic characteristics(the equilibrium temperature is 778℃), Xining meteorite is a L5 ordinary chondrite and beginning to change a L6. The degrees of shock metamorphism and terrestrial weathering are S3 and W0, respectively. The parent body of Xining meteorite had suffered impact and thermal metamorphism, which had resulted in fragmentation of chondrules, devitrification of glass, and recrystallization of matrix.

【基金/项目】 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 ; 广西隐伏金属矿产勘查重点实验室主任基金项目(13-A-01-02)

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