School of Geosciences, University of the Witwatersrand, Johannesburg, South Africa.
Centre for Planetary Science and Exploration, University of Western Ontario, London, Ontario, Canada.
Nat Commun. 2019 Jan 31;10(1):508. doi: 10.1038/s41467-019-08467-9.
Bolide impact is a ubiquitous geological process in the Solar System, which produced craters and basins filled with impact melt sheets on the terrestrial planets. However, it remains controversial whether these sheets were able to undergo large-scale igneous differentiation, or not. Here, we report on the discovery of large discrete bodies of melanorites that occur throughout almost the entire stratigraphy of the 1.85-billion-year-old Sudbury Igneous Complex (SIC) - the best exposed impact melt sheet on Earth - and use them to reaffirm that conspicuous norite-gabbro-granophyre stratigraphy of the SIC is produced by fractional crystallization of an originally homogeneous impact melt of granodioritic composition. This implies that more ancient and compositionally primitive Hadean impact melt sheets on the Earth and other terrestrial planets also underwent large-volume igneous differentiation. The near-surface differentiation of these giant impact melt sheets may therefore have contributed to the evolution and lithological diversity of the proto-crust on terrestrial planets.
火球撞击是太阳系中普遍存在的地质过程，它在类地行星上产生了撞击熔融层填充的陨石坑和盆地。然而，这些熔融层是否能够经历大规模的岩浆分异，仍然存在争议。在这里，我们报告了在 18.5 亿年的萨德伯里火成杂岩（SIC）中几乎整个地层中都存在大量离散的黑榴石岩体的发现——这是地球上暴露最好的撞击熔融层，并利用它们来再次确认 SIC 中明显的辉长岩-辉长闪长岩-花岗岩地层是由最初均一的花岗闪长质成分的撞击熔融体的分馏结晶产生的。这意味着，地球和其他类地行星上更古老和成分更原始的 Hadean 撞击熔融层也经历了大规模的岩浆分异。这些巨大的撞击熔融层的近地表分异可能对类地行星上的原地壳的演化和岩石多样性做出了贡献。
