The systematics of Cr (super 3+) and Cr (super 2+) partitioning between olivine and liquid in the presence of spinel

NASA, Johnson Space Center, Houston, TX, United States

The partitioning behavior of Cr into olivine in basaltic systems has been parameterized and can now be modeled over a wide range of redox conditions and liquid compositions. The Cr (super 2+) /Cr (super 3+) in spinel-saturated experimental systems can be estimated based on a simple model of Cr solubility in basalt. Fe (super 3+) appears to suppress the presence of Cr (super 2+) in basaltic systems. We predict that, in Fe-free systems, all Cr is trivalent at log f _O2 = -3 (i.e., QFM+3 to QFM-4), whereas all Cr is trivalent at approximately Ni-NiO(QFM+1) in Fe-bearing systems. Cr (super 2+) predominates under redox conditions O2 > or =QFM, appropriate for most terrestrial or martian basalts) strongly covaries with the ratio of non-bridging oxygens to tetrahedrally coordinated cations (NBO/T) (Mysen 1983) and can be estimated using the equation D (super (ol/liq)) (sub Cr3+) = -0.39.NBO/T+1.29. This relationship appears to be valid over the entire pressure range of olivine stability, from 1 atm to 15 GPa. D (sub Cr2+) (i.e., < or =IW-1, appropriate for lunar and some asteroidal basalts) is sensitive to liquid composition and temperature and can be estimated using either D (super (ol/liq)) (sub Cr2+) = 0.24.D (super (ol/liq)) _Mg -0.07 or D (super (ol/liq)) (sub Cr2+) = 0.66.[10.000/T(K)]-4.48. The 1/T equation is probably only valid at 1 atm pressure, but the D _Mg equation may be useful at higher pressures as well. The Cr content of spinel-saturated liquids is a function of temperature, composition, and f _O2 . However, the Cr content of spinel-saturated liquids is buffered by spinel and is insensitive to the bulk Cr content of the system (e.g., Roeder and Reynolds 1991). Therefore, the Cr content of a crystallizing, spinel-saturated basalt cannot be modeled using Raleigh fractionation models.

This record provided courtesy of AGI/GeoRef.

This article has been cited by other articles:

				G. Mallmann and H. St. C. O'Neill The Crystal/Melt Partitioning of V during Mantle Melting as a Function of Oxygen Fugacity Compared with some other Elements (Al, P, Ca, Sc, Ti, Cr, Fe, Ga, Y, Zr and Nb) J. Petrology, September 1, 2009; 50(9): 1765 - 1794. [Abstract] [Full Text] [PDF]

				C. D.K. Herd, R. E. Dwarzski, and C. K. Shearer The behavior of Co and Ni in olivine in planetary basalts: An experimental investigation American Mineralogist, February 1, 2009; 94(2-3): 244 - 255. [Abstract] [Full Text] [PDF]

				Z. Wan, L. A. Coogan, and D. Canil Experimental calibration of aluminum partitioning between olivine and spinel as a geothermometer American Mineralogist, July 1, 2008; 93(7): 1142 - 1147. [Abstract] [Full Text] [PDF]

				J.M. Karner, J.J. Papike, S.R. Sutton, C.K. Shearer, G. McKay, L. Le, and P. Burger Valence state partitioning of Cr between pyroxene-melt: Effects of pyroxene and melt composition and direct determination of Cr valence states by XANES. Application to Martian basalt QUE 94201 composition American Mineralogist, November 1, 2007; 92(11-12): 2002 - 2005. [Abstract] [Full Text] [PDF]

				J.M. Karner, J.J. Papike, C.K. Shearer, G. McKay, L. Le, and P. Burger Valence state partitioning of Cr and V between pyroxene-melt: Estimates of oxygen fugacity for martian basalt QUE 94201 American Mineralogist, July 1, 2007; 92(7): 1238 - 1241. [Abstract] [Full Text] [PDF]

				A. J. Berry, H. St.C. O'Neill, D. R. Scott, G. J. Foran, and J.M.G. Shelley The effect of composition on Cr2+/Cr3+ in silicate melts American Mineralogist, November 1, 2006; 91(11-12): 1901 - 1908. [Abstract] [Full Text] [PDF]

				C.K. Shearer, J.J. Papike, and J.M. Karner Pyroxene europium valence oxybarometer: Effects of pyroxene composition, melt composition, and crystallization kinetics American Mineralogist, October 1, 2006; 91(10): 1565 - 1573. [Abstract] [Full Text] [PDF]

				J.J. Papike, J.M. Karner, and C.K. Shearer Comparative planetary mineralogy: Valence state partitioning of Cr, Fe, Ti, and V among crystallographic sites in olivine, pyroxene, and spinel from planetary basalts American Mineralogist, February 1, 2005; 90(2-3): 277 - 290. [Abstract] [Full Text] [PDF]

				J. J. Papike, J.J. Papike, J.M. Karner, and C.K. Shearer Comparative planetary mineralogy: V/(Cr + Al) systematics in chromite as an indicator of relative oxygen fugacity American Mineralogist, October 1, 2004; 89(10): 1557 - 1560. [Abstract] [Full Text] [PDF]

				A. J. Berry, A. J. Berry, and H. St.C. O'Neill A XANES determination of the oxidation state of chromium in silicate glasses American Mineralogist, May 1, 2004; 89(5-6): 790 - 798. [Abstract] [Full Text] [PDF]

				J. Karner, J. Karner, JJ. Papike, and C.K. Shearer Olivine from planetary basalts: Chemical signatures that indicate planetary parentage and those that record igneous setting and process American Mineralogist, May 1, 2003; 88(5-6): 806 - 816. [Abstract] [Full Text] [PDF]

				A. A. Poustovetov and P. L. Roeder THE DISTRIBUTION OF Cr BETWEEN BASALTIC MELT AND CHROMIAN SPINEL AS AN OXYGEN GEOBAROMETER Can Mineral, April 1, 2001; 39(2): 309 - 317. [Abstract] [Full Text] [PDF]

				M. F. BRIGATTI, E. GALLI, L. MEDICI, L. POPPI, G. CIBIN, A. MARCELLI, and A. MOTTANA Chromium-containing muscovite: crystal chemistry and XANES spectroscopy European Journal of Mineralogy, April 1, 2001; 13(2): 377 - 389. [Abstract] [Full Text] [PDF]

				L. M. LARSEN and A. K. PEDERSEN Processes in High-Mg, High-T Magmas: Evidence from Olivine, Chromite and Glass in Palaeogene Picrites from West Greenland J. Petrology, July 1, 2000; 41(7): 1071 - 1098. [Abstract] [Full Text] [PDF]