High precision oxygen three‐isotope analyses of anhydrous chondritic interplanetary dust particles
High precision oxygen three‐isotope analyses of anhydrous chondritic interplanetary dust particles
复制标题
无水球粒状行星际尘埃颗粒的高精度氧三同位素分析
DOI：
--
复制
发表时间：
2012
期刊：
影响因子：
--
通讯作者：
N. Kita
中科院分区：
文献类型：
--
作者：
D. Nakashima;T. Ushikubo;M. Zolensky;N. Kita
摘要用2 μm小束离子探针分析了3个无水球粒星际尘埃粒子的氧三同位素比值。三个无水IdP的Δ17O值范围从−5‰到+1‰，与Wild2彗星和无水多孔IdP的硅酸铁颗粒的值重叠。首次在Δ17O值为每毫升几个的水平上解决了两个国内流离失所者体内氧同位素的不均一性。无水国内流离失所者是细粒硅酸盐(本研究中为≤3 μm)的松散集合体，仅含有少量粗粒硅酸盐(本研究中为2-20 μm)。另一方面，到目前为止分析的Wild 2粒子显示了相对粗粒化(≥Lowμm)的火成岩纹理。如果无水IdP代表来自彗星的细粒，那么无水IdP和Wild 2颗粒之间相似的Δ17O值可能意味着彗星结晶硅酸盐中的氧同位素比率是相似的，与晶体大小和结构无关。三个无水球粒陨石的Δ17O值范围也与碳质球粒陨石中的球粒陨石重叠，表明彗星尘粒(Wild 2颗粒和大多数无水IDP)与碳质球粒陨石之间存在成因联系。
Abstract– Oxygen three‐isotope ratios of three anhydrous chondritic interplanetary dust particles (IDPs) were analyzed using an ion microprobe with a 2 μm small beam. The three anhydrous IDPs show Δ17O values ranging from −5‰ to +1‰, which overlap with those of ferromagnesian silicate particles from comet Wild 2 and anhydrous porous IDPs. For the first time, internal oxygen isotope heterogeneity was resolved in two IDPs at the level of a few per mil in Δ17O values. Anhydrous IDPs are loose aggregates of fine‐grained silicates (≤3 μm in this study), with only a few coarse‐grained silicates (2–20 μm in this study). On the other hand, Wild 2 particles analyzed so far show relatively coarse‐grained (≥ few μm) igneous textures. If anhydrous IDPs represent fine‐grained particles from comets, the similar Δ17O values between anhydrous IDPs and Wild 2 particles may imply that oxygen isotope ratios in cometary crystalline silicates are similar, independent of crystal sizes and their textures. The range of Δ17O values of the three anhydrous IDPs overlaps also with that of chondrules in carbonaceous chondrites, suggesting a genetic link between cometary dust particles (Wild 2 particles and most anhydrous IDPs) and carbonaceous chondrite chondrules.