Experimental Petrology of the Basaltic Shergotite Yamato 980459: Implications for the Thermal Structure of the Martian Mantle

Donald S. Musselwhite (Lunar and Planetary Institute)
Heather A. Dalton (Arizona State University)
Walter S. Kiefer and Allan H. Treiman (Lunar and Planetary Institute)

Meteoritics and Planetary Science 41, 1271-1290, 2006.

Abstract: The martian meteorite Yamato 980459 is an olivine-phyric shergottite. It has a very primitive character and may be a primary melt of the martian mantle. We have conducted crystallization experiments on a synthetic Y-980459 composition at martian upper mantle conditions in order to test the primary mantle melt hypothesis. Results of these experiments indicate that the cores of the olivine megacrysts in Y-980459 are in equilibrium with a melt of bulk rock composition, suggesting that these megacrysts are in fact phenocrysts that grew from a magma of the bulk rock composition. Multiple saturation of the melt with olivine and a low-calcium pyroxene occurs at approximately 12 ± 0.5 kbars and 1540 ± 10 °C, suggesting that the meteorite represents a primary melt that separated from its mantle source at a depth of ~100 km. Several lines of evidence suggest that the Y-980459 source has undergone extensive melting prior to and/or during the magmatic event that produced the Y-980459 parent magma. When factored into convective models of the martian interior, the high temperature indicated for the upper martian mantle and possibly high melt fraction for the Y-980459 magmatic event suggest a signficantly higher temperature at the core mantle boundary than previously estimated.

Text of Article (on University of Arizona website)

Non-technical description of this work (on Planetary Science Research Discoveries website)

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Walter S. Kiefer,   kiefer@lpi.usra.edu