Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Variable refractory lithophile element compositions of planetary
  building blocks: insights from components of enstatite chondrites   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.

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The categories of this paper are: q-fin
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The categories of this paper are: nucl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: plasm-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: cond-mat
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The categories of this paper are: chem-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: adap-org
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The categories of this paper are: math
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The categories of this paper are: chao-dyn
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The categories of this paper are: econ
32
The categories of this paper are: atom-ph
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The categories of this paper are: q-bio
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The categories of this paper are: nlin
0
The categories of this paper are: hep-ph