论文标题
行星构建块的可变耐火岩性元素组成:来自Enstatite软骨的组成部分的见解
Variable refractory lithophile element compositions of planetary building blocks: insights from components of enstatite chondrites
论文作者
论文摘要
软骨是从太阳系历史最早阶段剩下的材料的沉积物。基于其未分化的性质和较少的分数化学成分,软骨被广泛认为代表了陆地行星及其胚胎的未加工的构件。基于软骨陨石中RLE比率的有限变化,陆生行星的化学成分通常发现散装体内难治性岩石元素元件(RLE)的软骨相对丰度(“恒定RLE比规则”)。在这里,我们表明RLE的比率,例如NB/TA,ZR/HF,SM/ND和Al/Ti,是从Enstatite软骨(EC)中的太阳值中分离的。在高度还原的环境下,单个EC软骨的分级RLE比率记录了RLE的不同核磷脂亲和力,并在软骨形成之前和/或或在软骨形成期间与含硅酸盐的含有RLE的硫化物分离。相比之下,批量EC具有类似太阳能的RLE比率,表明在EC母体积聚之前和期间,物理分类的硅酸盐和硫化物的物理排序可以忽略不计。同样,如果在多种同位素系统的支持下,地球的吸积以EC般的材料为主,则在地球的构建块中不应发生硅酸盐和硫化物的物理排序。另外,地球的前体可能是高温的雾化材料,由于含有RLE的硫化物的沉淀,在RLE分馏之前凝结了……高度降低的行星,这些行星经历了选择性去除或硅酸盐或金属/硫化物相的选择性去除或汞,例如水星,例如汞,可能具有分馏的非摩尔极构成bulk rle rle rle rle rle rle rle rle rle rle rle rle rle rle rle rle rle re rale。
Chondrites are sediments of materials left over from the earliest stage of the solar system history. Based on their undifferentiated nature and less fractionated chemical compositions, chondrites are widely considered to represent the unprocessed building blocks of the terrestrial planets and their embryos. Models of chemical composition of the terrestrial planets generally find chondritic relative abundances of refractory lithophile elements (RLE) in the bulk bodies ("constant RLE ratio rule"), based on limited variations of RLE ratios among chondritic meteorites and the solar photosphere. Here, we show that ratios of RLE, such as Nb/Ta, Zr/Hf, Sm/Nd and Al/Ti, are fractionated from the solar value in chondrules from enstatite chondrites (EC). The fractionated RLE ratios of individual EC chondrules document different chalcophile affinities of RLE under highly reducing environments and a separation of RLE-bearing sulfides from silicates before and/or during chondrule formation. In contrast, the bulk EC have solar-like RLE ratios, indicating that a physical sorting of silicates and sulfides was negligible before and during the accretion of EC parent bodies. Likewise, if the Earth's accretion were dominated by EC-like materials, as supported by multiple isotope systematics, the physical sorting of silicates and sulfides in the accretionary disk should not have occurred among the Earth's building blocks. Alternatively, the Earth's precursors might have been high-temperature nebular materials that condensed before the RLE fractionation due to precipitation of the RLE-bearing sulfides...Highly reduced planets that have experienced selective removal or accretion of silicates or metal/sulfide phases, such as Mercury, might have fractionated, non-solar bulk RLE ratios.