陨石氧同位素组成及其地学意义

doi:10.11867/j.issn.1001-8166.2000.05.0534

地球科学进展 ›› 2000, Vol. 15 ›› Issue (5): 534 -540. doi: 10.11867/j.issn.1001-8166.2000.05.0534

陨石氧同位素组成及其地学意义

侯渭,谢鸿森

中国科学院地球化学研究所,贵州贵阳 550002

收稿日期:2000-01-17 修回日期:2000-02-23 出版日期:2000-10-01
通讯作者: 侯渭(1942-),女,山西榆次人,研究员,主要从事陨石学和地球深部物质科学研究。
基金资助:
国家自然科学基金项目“高温高压下的熔体与流体混溶和分离研究”(编号:49772111)资助。

OXYGEN ISOTOPIC COMPOSITIONS OF METEORITES AND IT'S SIGNIFICANCE

HOU Wei, XIE Hong-sen

Institute of Geochemistry,Chinese Academy of Sciences,Guiyang 550002,China

Received:2000-01-17 Revised:2000-02-23 Online:2000-10-01 Published:2000-10-01

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介绍了各类陨石氧同位素组成的特点,对陨石氧同位素组成的主要成因观点进行了评述,结合地球的原始物质组成,讨论了陨石氧同位素组成的地球科学意义。

关键词: 陨石氧同位素, 陨石氧同位素成因, 地球原始物质组成

Oxygen isotopic compositions of meteorites and some hypotheses on it' s origin are reviewed. The following viewes about oxygen isotopic composition origin of chondrites and Earth are proposed: (1) Because of no clear that how much matters from out of solar system mixed into original solar nebular, the nebular may be taken for homogeneous oxygen isotopic composition. (2) The mass-dependent isotope fractionations occured by evaporation and gasification in early solar nebular, so that nebular became nebular gas with heterogeneous oxygen isotopic composition. In inner field of nebular(near original sun), the evaporation and gasification were stronger, and difference oxygen isotopic sources formed in difference position of nebular with varying temperature and pressure. (3) Some of nebular gas may undergo chemical reactions in which non-mass-dependent oxygen isotope fractionations occured, and its oxygen isotope possessedδ17O=δ18O.Then these nebular underwent condensation and formed many types of condensate, and these condensates can suffer aqueous alterations, melts, recondensation and accretion, finally
the bodies for different chondrite group formed. (4) The thermal metamorphism or partial melting can lead to a second mass-dependent oxygen isotope fractionation of the chondritic bodies. (5) Because those chemical reaction caused non-mass-dependent oxygen isotope fractionation occur under lower temperature and higher oxygen fugacity, the enstatite chondrites did not show appearance of no-mass-dependent oxygen isotope fractionation. (6) A few years ago the authors suggested that the 96% of primitive Earth was composed of quasi-enstatite chondrite planetesimal and quasi-enstatite achondrite planetesimal in previous paper. It can be seen from theδ17O-δ18O plot of this paper that oxygen isotopic composition of Earth is similar to that of enstatite chondrite,which indicites that the authors' s point on primitive Earth' s composition is reasonable.

Key words: Meteorite, Oxygen isotope, Original Earth composition.

中图分类号:

P578.94+2

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