Computer Science
Scientific paper
Jul 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994metic..29r.437a&link_type=abstract
Meteoritics (ISSN 0026-1114), vol. 29, no. 4, p. 437
Computer Science
Chemical Composition, Chondrites, Earth Core, Earth Mantle, Geochronology, Meteoritic Composition, Cosmochemistry, Iron Meteorites, Oxidation-Reduction Reactions, Pressure Effects, Refractory Metals, Siderites
Scientific paper
The present state of meteorite chemistry as established by Wasson and Kallemeyn allows us to emphasize the existence of simple relationships between a large number of elemental ratios. The estimate of the nonsiderophile refractory element ratio in the Earth's mantle allows us to place the Earth on the trend defined by meteorites. Concerning refractory elements, including Mg, Si, Sr, the Earth lies close to C1 meteorite as previously established. The estimate of siderophile/nonsiderophile refractory element ratios in the Earth's mantle, as well as on the meteorite trend permits us to estimate the composition of the Earth's core. In contrast to L and LL chondrites, Cr and Mn behave as siderophile elements in the Earth. This behavior is similar to EL chondrites. Constraints for the formation of L and LL chondrites is given. These results show the importance of the Red-Ox state evolution in the early Earth. This point is discussed, and we propose that the differentiation of the Earth starts in very reducing conditions but evolves to a more oxidizing one, in late stage near the surface. It is also shown that the core differentiated within the Earth at medium pressure. A similar approach based on volatile elements and using the terrestrial ratios K/U = 12,700 and Rb/Sr = 0.033 allows us to estimate the composition of the Earth's volatiles below Cv. A break in the distribution between volatile and nonvolatile elements corresponds to a 'model temperature formation' of 1200 deg. The partial pressure of S in this final stage is higher than the environment, which has formed ordinary chondrites. Those values are applied to estimate the I and Pb contents of the Earth and with the results of Xe and Pb in the terrestrial mantle we can revise the early chronology established by Patterson.
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