Possible formation of ancient crust on Mars through magma ocean processes

Elkins-Tanton, Linda T.; Hess, P. C.; Parmentier, E. M.

doi:10.1029/2005je002480

Cited by 174 publications

(218 citation statements)

References 72 publications

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“…For the Earth, any MO crystallization scenarios leading to persistent mantle stratification that is inconsistent with the structure of the present-day mantle can be ruled out. Pronounced stratification is expected for a single overturn of the compositionally stratified cumulate layers (Elkins-Tanton et al, 2005;Elkins-Tanton, 2008). In turn, initial stratification may be (partially) erased through progressive mixing due to multiple incremental cumulate overturns.…”

Section: Introductionmentioning

confidence: 99%

Reconciling magma‐ocean crystallization models with the present‐day structure of the Earth's mantle

Ballmer

Lourenço

Hirose

et al. 2017

Geochem Geophys Geosyst

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Terrestrial planets are thought to experience episode(s) of large‐scale melting early in their history. Fractionation during magma‐ocean freezing leads to unstable stratification within the related cumulate layers due to progressive iron enrichment upward, but the effects of incremental cumulate overturns during MO crystallization remain to be explored. Here, we use geodynamic models with a moving‐boundary approach to study convection and mixing within the growing cumulate layer, and thereafter within the fully crystallized mantle. For fractional crystallization, cumulates are efficiently stirred due to subsequent incremental overturns, except for strongly iron‐enriched late‐stage cumulates, which persist as a stably stratified layer at the base of the mantle for billions of years. Less extreme crystallization scenarios can lead to somewhat more subtle stratification. In any case, the long‐term preservation of at least a thin layer of extremely enriched cumulates with Fe# > 0.4, as predicted by all our models, is inconsistent with seismic constraints. Based on scaling relationships, however, we infer that final‐stage Fe‐rich magma‐ocean cumulates originally formed near the surface should have overturned as small diapirs, and hence undergone melting and reaction with the host rock during sinking. The resulting moderately iron‐enriched metasomatized/hybrid rock assemblages should have accumulated at the base of the mantle, potentially fed an intermittent basal magma ocean, and be preserved through the present‐day. Such moderately iron‐enriched rock assemblages can reconcile the physical properties of the large low shear‐wave velocity provinces in the present‐day lower mantle. Thus, we reveal Hadean melting and rock‐reaction processes by integrating magma‐ocean crystallization models with the seismic‐tomography snapshot.

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Section: Introductionmentioning

confidence: 99%

Reconciling magma‐ocean crystallization models with the present‐day structure of the Earth's mantle

Ballmer

Lourenço

Hirose

et al. 2017

Geochem Geophys Geosyst

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“…However, some return of volatiles into the mantle may be possible, even in the stagnant lid case, by delamination of lower crustal material (e.g. Dupeyrat and Sotin 1995;Van Thienen et al 2004a, 2004bElkins-Tanton 2007a, 2007b, assuming the sinking material contains volatile species. On Venus, the high atmospheric pressure may prevent exsolution of volatile species from lavas at the surface.…”

Section: Discussionmentioning

confidence: 99%

Water, Life, and Planetary Geodynamical Evolution

et al. 2007

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In our search for life on other planets over the past decades, we have come to understand that the solid terrestrial planets provide much more than merely a substrate on which life may develop. Large-scale exchange of heat and volatile species between planetary interiors and hydrospheres/atmospheres, as well as the presence of a magnetic field, are important factors contributing to the habitability of a planet. This chapter reviews these processes, their mutual interactions, and the role life plays in regulating or modulating them.

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“…During overturn upwelling of deep cumulates caused melting by adiabatic decompression, leading to segregation of garnet. Magmas generated by adiabatic decompression may have also resulted in forming the early Martian crust (Elkins-Tanton et al 2005a) …”

Section: Magma Ocean Crystallization and Cumulate Overturnmentioning

confidence: 99%

“…Debaille et al (2008) used the Sm-Nd and Lu-Hf isotope systematics of depleted shergottites to suggest a magma ocean depth of at least 1350 km. Finally, Elkins-Tanton et al (2003, 2005a, 2005b) argued on theoretical grounds that Mars could have been entirely molten due to the large amounts of heat present at the beginning of the solar system (see discussion above) and, therefore, proposed the possibility of a magma ocean reaching down all the way to the core-mantle boundary (∼2000 km in Mars). Such a deep magma ocean, however, seems to be inconsistent with the observed depletions of moderately siderophile elements in the Martian mantle (Righter and Chabot 2011), unless metal-silicate equilibration occurred at different depths and models derived from trace element partitioning would thus yield an "average depth" of metal-silicate separation.…”

Section: Magma Ocean and Core Formation On Marsmentioning

confidence: 99%

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Core Formation and Mantle Differentiation on Mars

Mezger¹,

Debaille²,

Kleine³

2012

Quantifying the Martian Geochemical Reservoirs

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Geochemical investigation of Martian meteorites (SNC meteorites) yields important constraints on the chemical and geodynamical evolution of Mars. These samples may not be representative of the whole of Mars; however, they provide constraints on the early differentiation processes on Mars. The bulk composition of Martian samples implies the presence of a metallic core that formed concurrently as the planet accreted. The strong depletion of highly siderophile elements in the Martian mantle is only possible if Mars had a large scale magma ocean early in its history allowing efficient separation of a metallic melt from molten silicate. The solidification of the magma ocean created chemical heterogeneities whose ancient origin is manifested in the heterogeneous 142 Nd and 182 W abundances observed in different meteorite groups derived from Mars. The isotope anomalies measured in SNC meteorites imply major chemical fractionation within the Martian mantle during the life time of the short-lived isotopes 146 Sm and 182 Hf. The Hf-W data are consistent with very rapid accretion of Mars within a few million years or, alternatively, a more protracted accretion history involving several large impacts and incomplete metal-silicate equilibration during core formation. In contrast to Earth early-formed chemical heterogeneities are still preserved on Mars, albeit slightly modified by mixing processes. The preservation of such ancient chemical differences is only possible if Mars did not undergo efficient whole mantle convection or vigorous plate tectonic style processes after the first few tens of millions of years of its history. K. Mezger ( )

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Possible formation of ancient crust on Mars through magma ocean processes

Cited by 174 publications

References 72 publications

Reconciling magma‐ocean crystallization models with the present‐day structure of the Earth's mantle

Reconciling magma‐ocean crystallization models with the present‐day structure of the Earth's mantle

Water, Life, and Planetary Geodynamical Evolution

Core Formation and Mantle Differentiation on Mars

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