Statistics – Methodology
Scientific paper
Dec 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufmdi43a1949w&link_type=abstract
American Geophysical Union, Fall Meeting 2010, abstract #DI43A-1949
Statistics
Methodology
[1015] Geochemistry / Composition Of The Core, [1027] Geochemistry / Composition Of The Planets, [3610] Mineralogy And Petrology / Geochemical Modeling, [3630] Mineralogy And Petrology / Experimental Mineralogy And Petrology
Scientific paper
Although core formation was ubiquitous within the inner Solar system [1] the conditions of pressure, temperature and oxidation state under which it took place are difficult to estimate without precise knowledge of the composition of the body of interest. In contrast, better constraints are available on the timing of accretion from the short-lived 182Hf-182W system. The latter demonstrates a broad correlation between asteroidal and planetary size and the timescale of accretion [2]. Our purpose here is to derive a clearer understanding of the differences between the conditions of accretion and differentiation on Earth, Mars, the moon and different asteroidal bodies. The approach requires an estimate of the average composition of the planetary mantle combined with experimental data on the partitioning of a wide range of elements between metallic and silicate liquids and between silicate crystals and melts. When applied to the Earth this methodology indicates that Earth started accreting as a small reduced body and progressively added more oxidised and volatile-rich material as it grew. We began by testing a number of models of the compositions of the mantles of the moon, Mars and the HED parent body using experimental phase equilibrium data to determine whether the proposed compositions can yield the observed igneous rocks. Using the best-fit mantle compositions we then calculated the fractionation paths (dominated by olivine and pyroxene) which most closely reproduce the observed trends in major element compositions. Using the major element model as a starting point, we then calculated trace-element fractionation trends, using experimentally determined mineral-melt partition coefficients, in order to back-calculate the trace-element concentrations in the mantle. Uncertainties in this procedure are least for highly incompatible elements such as Mo and W and most for elements such as Ni which partition strongly into olivine. We used the calculated mantle compositions to estimate the conditions of accretion and core formation on the different bodies. This involved using a large set of experimental data (our own results and those of other workers) on metal-silicate partitioning of Mo, W, Ni, Co, V and Cr. We model these data in terms of pressure, temperature, metal composition, silicate composition and oxygen fugacity. When the partitioning data are applied to planetary and asteroidal bodies we find, unsurprisingly, that the pressure and temperature of accretion increases with planet size. We also find, however, a decrease in oxygen fugacity with increasing size, plausibly reflecting radial differences in the oxidation state of Fe within the inner solar system. 1. Greenwood, R.C., et al., Widespread magma oceans on asteroidal bodies in the early Solar System. Nature, 2005. 435(7044): p. 916-918. 2. Kleine, T., et al., Rapid accretion and early core formation on asteroids and the terrestrial planets from Hf-W chronometry. Nature, 2002. 418(6901): p. 952-955.
Tuff James
Wade Jeremy
Wood Bernard J.
No associations
LandOfFree
Conditions of accretion and core formation in the inner solar system does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Conditions of accretion and core formation in the inner solar system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Conditions of accretion and core formation in the inner solar system will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1500832