论文标题
碰撞侵蚀对大钉模型中地球 - 阿纳格行星组成的影响:对地球形成的影响
The effect of collisional erosion on the composition of Earth-analog planets in Grand Tack models: Implications for the formation of the Earth
论文作者
论文摘要
撞击引起的陆地积聚过程中地球早期地壳的侵蚀可以显着改变大块硅酸盐土的原始化学成分(即BSE,即添加到当今地幔中的地壳的组成)。特别是,它可以特别有效地改变对硅酸盐熔体具有很强亲和力(即不兼容的元素)的丰富性,因为早期分化的外壳优先富集了这些外壳。在这里,我们进一步开发了侵蚀模型(EROD),以量化碰撞侵蚀对BSE最终组成的影响。将结果与当今的BSE组成模型进行了比较,并提供了地球吸积过程的约束。在大钉模型的背景下,针对大约50个地球类似物的整个积聚历史计算了由地壳剥离产生的BSE化学成分的演变。所选的化学元件跨越了广泛的不兼容度。我们发现,当由低部分熔融速率形成地壳时,在BSE中,最不兼容的岩石,TH或U等最不兼容的岩石元素的最大损失可能会达到40wt%。因此,取决于增生过程中地壳形成过程的确切性质和增生历史本身,难治性的岩性元素(RLE)可能不在BSE中的软骨相对比例。在这种情况下,可能需要根据这些元素的地球化学不相容性来校正当前的BSE估计。另外,如果RLE确实处于BSE中的软骨相对比例,则应质疑有效影响BSE化学组成的积聚场景。
Impact-induced erosion of the Earth's early crust during accretion of terrestrial bodies can significantly modify the primordial chemical composition of the Bulk Silicate Earth (BSE, that is, the composition of the crust added to the present-day mantle). In particular, it can be particularly efficient in altering the abundances of elements having a strong affinity for silicate melts (i.e. incompatible elements) as the early differentiated crust was preferentially enriched in those. Here, we further develop an erosion model (EROD) to quantify the effects of collisional erosion on the final composition of the BSE. Results are compared to the present-day BSE composition models and constraints on Earth's accretion processes are provided. The evolution of the BSE chemical composition resulting from crustal stripping is computed for entire accretion histories of about 50 Earth analogs in the context of the Grand Tack model. The chosen chemical elements span a wide range of incompatibility degrees. We find that a maximum loss of 40wt% can be expected for the most incompatible lithophile elements such as Rb, Th or U in the BSE when the crust is formed from low partial melting rates. Accordingly, depending on both the exact nature of the crust-forming processes during accretion and the accretion history itself, Refractory Lithophile Elements (RLE) may not be in chondritic relative proportions in the BSE. In that case, current BSE estimates may need to be corrected as a function of the geochemical incompatibility of these elements. Alternatively, if RLE are indeed in chondritic relative proportions in the BSE, accretion scenarios that are efficient in affecting the BSE chemical composition should be questioned.