Characterization of Presolar Silicate and Oxide Grains in Primitive Carbonaceous Chondrites
Characterization of Presolar Silicate and Oxide Grains in Primitive Carbonaceous Chondrites
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原始碳质球粒陨石中太阳前硅酸盐和氧化物颗粒的表征
DOI：
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发表时间：
2007
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影响因子：
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通讯作者：
L. Nittler
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文献类型：
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作者：
A. Nguyen;F. Stadermann;E. Zinner;R. Stroud;C. Alexander;L. Nittler
用NanoSIMS离子微探针对氧同位素进行光栅离子成像，已用于识别两种原始陨石中的前太阳颗粒。在原始碳质球粒陨石Acfer 094中发现了11种前太阳级硅酸盐和8种前太阳级氧化物，丰度分别为百万分之325和360。此外，9 presolar硅酸盐和5 presolar氧化物颗粒中确定的CO3球粒陨石ALHA 77307，为320和200 ppm的丰度，分别。这些丰度，这是矩阵归一化和仪器检测效率校正，是远远高于其他presolar阶段，除了纳米金刚石，虽然后者可能不是所有的presolar。利用俄歇光谱对ALHA 77307中六个前太阳硅酸盐颗粒的化学组成进行了分析。一个presolar硅酸盐颗粒的透射电子显微镜（TEM）分析显示，非化学计量的组合物和非晶结构所示的扩散电子衍射图案。太阳前硅酸盐的氧同位素组成表明起源于红巨星和渐近巨星分支星。10个前太阳系硅酸盐的硅同位素组成的分析提供了进一步的限制银河系化学演化的影响。
Raster ion imaging of the oxygen isotopes with the NanoSIMS ion microprobe has been used to identify presolar grains in two primitive meteorites. Eleven presolar silicates and eight presolar oxides were identified in the primitive carbonaceous chondrite Acfer 094 for abundances of 325 and 360 parts per million (ppm), respectively. In addition, nine presolar silicates and five presolar oxide grains were identified in the CO3 chondrite ALHA 77307, for abundances of 320 and 200 ppm, respectively. These abundances, which are matrix-normalized and corrected for instrumental detection efficiencies, are much higher than those of other presolar phases, with the exception of nanodiamonds, although the latter may not all be presolar. The chemical compositions of six presolar silicate grains from ALHA 77307 were elucidated by Auger spectroscopy. Transmission electron microscopy (TEM) analysis of one presolar silicate grain revealed a nonstoichiometric composition and an amorphous structure as indicated by the diffuse electron diffraction pattern. The oxygen isotopic compositions of the presolar silicates indicate origins in red giant and asymptotic giant branch stars. Analysis of the Si isotopic compositions of 10 presolar silicates provides further constraints on the effects of Galactic chemical evolution.