Redox State of Mars' Upper Mantle and Crust from Eu Anomalies in Shergottite Pyroxenes

The oxidation state of basaltic martian meteorites is determined from the partitioning of europium (Eu) in their pyroxenes. The estimated redox conditions for these samples correlate with their initial neodymium and strontium isotopic compositions. This is interpreted to imply varying degrees of interaction between the basaltic parent melts, derived from a source in the martian mantle, and a crustal component. Thus, the mantle source of these martian basalts may have a redox state close to that of the iron-wüstite buffer, whereas the martian crust may be more oxidized (with a redox state higher than or equal to that of the quartz-fayalite-magnetite buffer). A difference in redox state of more than 3 log units between mantle and crustal reservoirs on Mars could result from oxidation of the crust by a process such as aqueous alteration, together with a subsequent lack of recycling of this oxidized crust through the reduced upper mantle.

[1]  John H. Jones.  A discussion of isotopic systematics and mineral zoning in the shergottites - Evidence for a 180 m.y. igneous crystallization age , 1986 .

[2]  H. McSween,et al.  Geochemical evidence for magmatic water within Mars from pyroxenes in the Shergotty meteorite , 2001, Nature.

[3]  L. Taylor,et al.  Martian basalt (shergottite) Queen Alexandra Range 94201 and lunar basalt 15555: A tale of two pyroxenes , 1998 .

[4]  G. Mckay,et al.  Chronology and petrogenesis of young achondrites, Shergotty, Zagami, and ALHA77005 - Late magmatism on a geologically active planet , 1982 .

[5]  R. Clayton,et al.  Los Angeles: The Most Differentiated Basaltic Martian Meteorite , 2000 .

[6]  H. McSween,et al.  Petrogenesis of shergottite meteorites inferred from minor and trace element microdistributions , 1994 .

[7]  M. Malin,et al.  Evidence for recent groundwater seepage and surface runoff on Mars. , 2000, Science.

[8]  H. Wänke,et al.  Volatiles on Earth and Mars: A comparison , 1987 .

[9]  G. Mckay,et al.  Clinopyroxene REE distribution coefficients for shergottites: The REE content of the Shergotty melt☆ , 1986 .

[10]  J. Blichert‐Toft,et al.  Bulk chemistry of Saharan shergottite Dar al Gani 476 , 2001 .

[11]  L. Leshin.  Insights into Martian water reservoirs from analyses of Martian meteorite QUE94201 , 2000 .

[12]  D. L. Anderson.  Internal constitution of Mars. , 1972 .

[13]  H. McSween,et al.  Petrology and origin of the shergottite meteorites , 1979 .

[14]  Joshua R. Smith,et al.  The mantle of Mars: Some possible geological implications of its high density , 1978 .

[15]  E. Stolper.  Experimental petrology of eucritic meteorites , 1977 .

[16]  C. Langmuir,et al.  Oxidation states of mid-ocean ridge basalt glasses , 1986 .

[17]  B. Wood,et al.  Mantle Oxidation State and Its Relationship to Tectonic Environment and Fluid Speciation , 1990, Science.

[18]  H. McSween,et al.  A petrologic and trace element study of Dar al Gani 476 and Dar al Gani 489: Twin meteorites with affinities to basaltic and lherzolitic shergottites , 2001 .

[19]  H. McSween,et al.  Petrogenesis of the Elephant Moraine A79001 meteorite Multiple magma pulses on the shergottite parent body , 1983 .

[20]  L. E. Nyquist,et al.  Constraints on Martian differentiation processes from RbSr and SmNd isotopic analyses of the basaltic shergottite QUE 94201 , 1997 .

[21]  Harry Y. McSween,et al.  What we have learned about Mars from SNC meteorites , 1994 .

[22]  S. Haggerty,et al.  Redox state of Earth's upper mantle from kimberlitic ilmenites , 1983, Nature.

[23]  L. Taylor,et al.  QUE94201 shergottite: Crystallization of a Martian basaltic magma , 1996 .

[24]  John W. Morgan,et al.  Chemical composition of Mars , 1979 .

[25]  L. L. Lundberg,et al.  Rare earth element carriers in the Shergotty meteorite and implications for its chronology , 1988 .

[26]  H. Wiesmann,et al.  Rb-Sr age of the Shergotty achondrite and implications for metamorphic resetting of isochron ages , 1979 .

[27]  H. McSween,et al.  Re-evaluation of intercumulus liquid composition and oxidation state for the Shergotty meteorite , 1999 .

[28]  L. Le,et al.  Experimental partitioning of rare earth elements and strontium: Constraints on petrogenesis and redox conditions during crystallization of Antarctic angrite Lewis Cliff 86010 , 1994 .

[29]  S. Saxena.  Oxidation state of the mantle , 1989 .

[30]  Mark S. Ghiorso,et al.  Chemical mass transfer in magmatic processes IV. A revised and internally consistent thermodynamic model for the interpolation and extrapolation of liquid-solid equilibria in magmatic systems at elevated temperatures and pressures , 1995 .