Deep Martian Mantle Melting and Implications for the Source Regions of Martian Basalts
Abstract
The chemical compositions of Martian SNC meteorites (Shergotty, Nakhla and Chassigny types) show significant variations in major and trace element contents, suggesting that parental magmas originate from different geochemical reservoirs. Radiogenic isotope systematics further indicate that some reservoirs were strongly influenced by silicate differentiation processes about 4.5 Gyr ago, placing such events in tight vicinity to core formation, and therefore favour magma ocean crystallisation and differentiation as a plausible mechanism for generating a diversity of sources. However, any predictions of geochemical signatures resulting from large scale magma ocean differentiation require precise knowledge of melting relations of a primordial bulk silicate Mars composition to be known. The aim of this study is to investigate solidus and liquids temperatures, mineral modes and melt fractions for the bulk silicate Mars (BSM) composition proposed by Taylor (2013, Chemie der Erde 73, 401-420) in a self consistent set of experiments from ambient to core-mantle boundary (estimated at around 20 GPa) pressures. Specific emphasis is put on the presure range greater than 10 GPa to more rigorously investigate the potential role of majoritic garnet during magma ocean differentiation. The new results, combined with data from previous studies on phase relations and mineral-melt element partitioning, are being used to derive time-integrated geochemical models to discuss fractionation mechanisms that could lead to the distinct chemical signatures of source regions proposed for martian meteorites.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFM.P23A2160L
- Keywords:
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- 6297 Instruments and techniques;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTSDE: 6299 General or miscellaneous;
- PLANETARY SCIENCES: SOLAR SYSTEM OBJECTSDE: 5494 Instruments and techniques;
- PLANETARY SCIENCES: SOLID SURFACE PLANETSDE: 5499 General or miscellaneous;
- PLANETARY SCIENCES: SOLID SURFACE PLANETS