Partial Melting Experiments on an Mg # 80 Martian Mantle and Their Implications for Basalt Genesis

Author

Zachary Adam Chartrand, Southern Illinois University CarbondaleFollow

Date of Award

8-1-2014

Degree Name

Master of Science

Department

Geology

First Advisor

Filiberto, Justin

Abstract

Dreibus and Wänke (1985) calculated a bulk composition for the interior of Mars (DW model) based on eight Martian meteorites. Since then, experiments on the Martian interior have used this model, or similar models, to understand processes that may influence basalt genesis within the Martian mantle. Recent experiments have shown that the DW model does not fit with the current, now greater number of Martian meteorites (132 including paired stones as of April 2014) and surface basalt compositions. One of the parameters that does not match is the Mg # (atomic [Mg2+/(Mg2+ + Fe2+)]*100); the current data show that Mars is not as iron rich as once thought and needs a higher bulk Mg # for the mantle to produce Martian basaltic compositions. This project involves experiments using a new bulk composition with an Mg # of 80 to update the compositions of a partially melted Martian mantle. A melt produced by this new bulk composition consists of MgO and FeO levels that match well with the primitive Martian meteorite Yamato-980459. Additionally, this composition was produced with 37% melt. Melts produced with this bulk composition match poorly with Na₂O composition of Martian meteorites and match better, but still not particularly well, with CaO and Al₂O₃ compositions. However, lower-temperature partial melts of the Mg # 80 mantle match well with CaO, Al₂O₃, FeO, and Na₂O compositions of Martian surface basalts. This shows that the source of the surface basalts is represented well by the model in this study.