Rare earth elements clinopyroxenes

Rare earth element data will also serve as the basis for a forward modeling study to better constrain melting systematics in the Galapagos. The melting model will invoke clinopyroxene-rare earth element partition coefficients, which vary with composition (Gallahan and Nielsen, 1992), and a polybaric or column melting process. 

Blundy JD, Wood BJ, Davies A (1996) Thermodynamics of rare earth element partitioning between clinopyroxene and melt in the system Ca0-Mg0-Al203-Si02. Geochim Cosmochim Acta 60 359-364 Blundy JD, Robinson JAC, Wood BJ (1998) Heavy REE are compatible in clinopyroxene on the spinel Iherzolite solidus. Earth Planet Sci Lett 160 493-504... 

Assuming that half a percent liquid is trapped with the residue, equating the concentration in the rock to that in the solid residue will result in a severe bias for incompatible elements with Df<0.01 and in pure nonsense for elements with Dt<0.001. A typical example is represented by rare-earth elements in peridotites. Even separated clinopyroxenes can be suspected to have incorporated most of the REE from whichever trace amounts of liquid happened to be trapped in the cooling rock. If the rest of the minerals do not take any REE, it is left to the reader as an exercise to show that the concentration in clinopyroxene after uptake of incompatible elements is related to that in the clinopyroxene from a liquid-free residual peridotite through... 

Wood B. J. and Blundy J. D. (1997) A predictive model for rare earth element partitioning between clinopyroxene and anhydrous silicate melt. Contrib. Mineral. Petrol. 129, 166-181. 

Shimizu N. (1975) Rare earth elements in garnets and clinopyroxenes from garnet Uierzolite nodules in kimberlites. Earth Planet Sci. Lett 25, 26-35. 

Gaetani G. A. and Grove T. L. (1995) Partitioning of rare-earth elements between clinopyroxene and silicate melt crystal-chemical controls. Geochim. Cosmochim. Acta 59, 1951-1962. 

Hack P. J., Nielsen R. L. and Johnston A. D. (1994) Experimentally-determined rare-earth element and Y partitioning behaviour between clinopyroxene and basaltic liquids at pressures up to 20 kbar. Chem. Geol. 117, 89-105. 

Nicholls I. A. and Harris K. L. (1980) Experimental rare earth element partition coefficients for garnet, clinopyroxene and amphibole coexisting with andesitic and basaltic liquids. Geochim. Cosmochim. Acta 34, 331-340. 

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Green, T. H., and N. J. Pearson, Rare earth element partitioning between clinopyroxene and silicate liquid at moderate to high pressure, Cont. Mineral. Petrol., 9J. 24-36, 1985. 

Vanned R., Shimizu N., Bottazzi P., OttoliniL., Piccardo G. B., and Rampone E. (1991) Rare earth and trace element geochemistry of clinopyroxenes from the Zabargad perido-tite-pyroxenite association. J. Petrol. (Orogenic Iherzolites and mantle processes), 244- 255. 

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