CO3 .0球粒陨石自治领08006中前太阳粒和$^{15}$富氮有机质的高丰度
High Abundances of Presolar Grains and $^{15}$N-rich Organic Matter in CO3.0 Chondrite Dominion Range 08006
摘要：
对CO3.0球粒陨石Dominion Range（DOM）08006基质的NanoSIMS C-、N-和O-同位素绘图显示，它的基质中富含太阳前富O颗粒（257 + 76/ -96 ppm，2 $σ$），是所有陨石中丰度最高的。它还具有35（+25 /-17，2 $σ$）ppm的前太阳能SiC的基质丰度，类似于在原始球粒陨石类中看到的。这为大量同位素和岩石学证据提供了额外的支持，证明DOM 08006是已知最原始的CO陨石。五个presolar硅酸盐颗粒的透射电子显微镜显示一个具有复合矿物学类似于较大的变形橄榄石聚集体和平衡冷凝，两个非化学计量的无定形颗粒和两个橄榄石颗粒一致，虽然一个被确定为这样的完全基于其组成。我们还发现，不溶性有机物（IOM）主要是目前作为亚微米夹杂物的C-和N-同位素异常的范围类似于原始CR陨石和行星际尘埃颗粒中看到的。与其他原始外星物质相比，氢同位素成像显示正常和均匀的D/H。最有可能的是，DOM 08006和其他CO陨石中增加了类似的补充原始和同位素异常的有机物质，在其他球粒陨石类和IDP中发现，但非常有限的热变质作用DOM 08006经历了导致富含D的有机部分的损失，而不是实质上影响的C和N异常的分子载体或大多数无机相的陨石。一个富含碳的颗粒，是高度缺乏$^{13}$ C和$^{15}$ N被确定，我们认为它起源于太阳的父母分子云。
英文摘要：
NanoSIMS C-, N-, and O-isotopic mapping of matrix in CO3.0 chondrite Dominion Range (DOM) 08006 revealed it to have in its matrix the highest abundance of presolar O-rich grains (257 +76 / -96 ppm, 2$σ$) of any meteorite. It also has a matrix abundance of presolar SiC of 35 (+25 / -17, 2$σ$) ppm, similar to that seen across primitive chondrite classes. This provides additional support to bulk isotopic and petrologic evidence that DOM 08006 is the most primitive known CO meteorite. Transmission electron microscopy of five presolar silicate grains revealed one to have a composite mineralogy similar to larger amoeboid olivine aggregates and consistent with equilibrium condensation, two non-stoichiometric amorphous grains and two olivine grains, though one is identified as such solely based on its composition. We also found insoluble organic matter (IOM) to be present primarily as sub-micron inclusions with ranges of C- and N-isotopic anomalies similar to those seen in primitive CR chondrites and interplanetary dust particles. In contrast to other primitive extraterrestrial materials, H isotopic imaging showed normal and homogeneous D/H. Most likely, DOM 08006 and other CO chondrites accreted a similar complement of primitive and isotopically anomalous organic matter to that found in other chondrite classes and IDPs, but the very limited amount of thermal metamorphism experienced by DOM 08006 has caused loss of D-rich organic moieties, while not substantially affecting either the molecular carriers of C and N anomalies or most inorganic phases in the meteorite. One C-rich grain that was highly depleted in $^{13}$C and $^{15}$N was identified; we propose it originated in the Sun's parental molecular cloud.
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