High-Fe, Low-Al Basalts: Evidence of Extensive Mantle Processing on Earth, Moon, Mars, Vesta, Venus, and Io

Ferropicrite basalts – basalts with relatively high-Fe and low-Al contents compared to ‘normal' basalts – are a minor but widespread component of magmatism on Earth. We have investigated how widespread high-Fe, low-Al compositions (similar to ferropicrites) are on other terrestrial planetary bodies and suggest that these basalts formed through similar processes.

High-Fe, low-Al igneous compositions have been found on the Earth, Moon, Mars, Vesta, and possibly on Venus and Io. Therefore they are not unique to one planetary body, but seem to be widespread throughout terrestrial bodies in the solar system. This suggests that similar processes could be occurring to produce these compositions on different planetary bodies. The common factor required to produce such compositions on all the planetary bodies under consideration is an extensively processed mantle source region, through a magma ocean or repeated partial melting episodes. Magma ocean models (Hofmeister, 1983) have shown that Mg-, Fe-rich minerals sink thereby producing a Mg- Fe-rich residual mantle. If these minerals were re-melted during rehomogenization, or mantle overturn, then high -Mg, -Fe, low -Al basalts could be produced. Such a model has been suggested for Mars (Debaille et al., 2007; Elkins-Tanton et al., 2003), the moon (Elkins Tanton et al., 2002; Warren, 1985), Vesta (Righter and Drake, 1997), Io (Keszthelyi and McEwen, 1997), Venus (Elkins-Tanton et al., 2007), and the Earth (Hofmeister, 1983), but now may be extrapolated to any planet that has undergone extensive mantle processing. Therefore, finding such high-Fe, low-Al compositions on other terrestrial bodies gives an indication about the extent of mantle processing.