Williams Curtis D, Sanborn Matthew E, Defouilloy Céline, Yin Qing-Zhu, Kita Noriko T, Ebel Denton S, Yamakawa Akane, Yamashita Katsuyuki
Department of Earth and Planetary Sciences, University of California, Davis, CA 95616;
Department of Earth and Planetary Sciences, University of California, Davis, CA 95616.
Proc Natl Acad Sci U S A. 2020 Sep 22;117(38):23426-23435. doi: 10.1073/pnas.2005235117. Epub 2020 Sep 8.
Dynamic models of the protoplanetary disk indicate there should be large-scale material transport in and out of the inner Solar System, but direct evidence for such transport is scarce. Here we show that the εTi-εCr-ΔO systematics of large individual chondrules, which typically formed 2 to 3 My after the formation of the first solids in the Solar System, indicate certain meteorites (CV and CK chondrites) that formed in the outer Solar System accreted an assortment of both inner and outer Solar System materials, as well as material previously unidentified through the analysis of bulk meteorites. Mixing with primordial refractory components reveals a "missing reservoir" that bridges the gap between inner and outer Solar System materials. We also observe chondrules with positive εTi and εCr plot with a constant offset below the primitive chondrule mineral line (PCM), indicating that they are on the slope ∼1.0 in the oxygen three-isotope diagram. In contrast, chondrules with negative εTi and εCr increasingly deviate above from PCM line with increasing δO, suggesting that they are on a mixing trend with an ordinary chondrite-like isotope reservoir. Furthermore, the ΔO-Mg# systematics of these chondrules indicate they formed in environments characterized by distinct abundances of dust and HO ice. We posit that large-scale outward transport of nominally inner Solar System materials most likely occurred along the midplane associated with a viscously evolving disk and that CV and CK chondrules formed in local regions of enhanced gas pressure and dust density created by the formation of Jupiter.
原行星盘的动力学模型表明,应该存在大规模的物质进出内太阳系的运输,但这种运输的直接证据却很稀少。在这里,我们表明,大型单个球粒陨石的εTi-εCr-ΔO系统特征(这些球粒陨石通常在太阳系中第一批固体形成后2至3百万年形成)表明,在太阳系外部形成的某些陨石(CV和CK球粒陨石)吸积了内太阳系和外太阳系的各种物质,以及通过对整体陨石分析以前未识别的物质。与原始难熔成分的混合揭示了一个“缺失储库”,它弥合了内太阳系和外太阳系物质之间的差距。我们还观察到,具有正εTi和εCr的球粒陨石在原始球粒陨石矿物线(PCM)下方有恒定偏移的图上,这表明它们在氧三同位素图上的斜率约为1.0。相比之下,具有负εTi和εCr的球粒陨石随着δO的增加越来越偏离PCM线,这表明它们与普通球粒陨石样同位素储库呈混合趋势。此外,这些球粒陨石的ΔO-Mg#系统特征表明它们形成于具有不同尘埃和HO冰丰度特征的环境中。我们推测,名义上内太阳系物质的大规模向外运输最有可能沿着与粘性演化盘相关的中平面发生,并认为CV和CK球粒陨石形成于由木星形成产生的气体压力和尘埃密度增强的局部区域。