Experimental petrology of the basaltic shergottite Yamato-980459: Implications for the thermal structure of the Martian mantle
Authors: Musselwhite, Donald S.; Dalton, Heather A.; Kiefer, Walter S.; Treiman, Allan H.
Source: Meteoritics & Planetary Science, Volume 41, Issue 9, Pages 1271-1419 (September 2006) , pp. 1271-1290(20)
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Abstract:
The Martian meteorite Yamato (Y-) 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 kbar 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 underwent 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 suggests a significantly higher temperature at the core-mantle boundary than previously estimated.Document Type: Research article
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