| 其他摘要 | The enstatite chondrites are a small group with unusual chemical and mineralogical compositions. As they were formed in a unique reducing enviroment, they exhibit a number of unique properities that are significantly different from those of carbonaceous and ordinary chondrites. For example, the material sources of the parent body, formation location, redox enviroment, accretion temperature of the parent body, metamorphism and number of the parent bodies, the genetic connection between enstatite chondrites and aubrites are still of great debate. In order to determine trace element abundances as indicative elements in complex sulfide assembleges of the most unequilibrated enstatite chondrites-Qingzhen (EH3), which preserves the texture and chemical imprint of early solar nebular processes, we have established the methods of separating mineral grains from polished sections of meteorites and analyzed them by INAA on the basis of repeated experiments. The chemical compositions and trace element abundances of oldhamite, niningerite, alabandite, djerfisherite, troilite and minerals A, B and Qingzhen and some other enstatite chondrites have been determined by electron microprobe and INAA. To sum up, the research results of Qingzhen and some other enstatite chondrites as well as aubrites with respect to their petrologic mineralogy, mineralogical chemistry, bulk chemistry, chronology and isotopic composition as well as trace element abundances of sulfides provide evidence suggesting that parent materials of enstatite chondrites came from the nebulae of solar composition, the formation location is ≤0.7AU far from the sun, the nebula is enriched in H and C so that the apparent effect is similar to one of C/O ≥ 1, nebular pressure is 10~(-2)-10~(-4) atm., accretion temperature of the parent bodies is 600-700K, the trace elements in sulfides were re-ditributed during metamorphism, EH and EL chondrites were derived from different parent bodies, aubrites are of magmatic differentiation origin. We have outlined the general picture of the formation and evolution of Qingzhen enstatite chondrite and its parent body on the basis of the above results. |
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