TY - JOUR
T1 - Trace element partitioning between orthopyroxene and anhydrous silicate melt on the lherzolite solidus from 1.1 to 3.2 GPa and 1,230 to 1,535°C in the model system Na2O–CaO–MgO–Al2O3–SiO2
AU - Frei, Dirk
AU - Liebscher, Axel
AU - Franz, Gerhard
AU - Wunder, Bernd
AU - Klemme, Stephan
AU - Blundy, Jon
N1 - Funding Information:
Acknowledgments We thank the DFG for supporting this work by grant number FR 557/17-1 to GF. DF thanks Wilhelm Heinrich for generously granting access to experimental and analytical facilities at the GFZ Potsdam. DF and JB greatly acknowledge access to the NSS Edinburgh ion microprobe facility granted by NERC. We are indebted to John Craven, Simone Kasemann and Richard Hinton for their efforts and help with ion microprobe analysis, and to Oona Appelt (GFZ Potsdam) and Berit Wenzel (University of Copenhagen) for their help with the EMPA. This paper is published with the permission of the Geological Survey of Denmark and Greenland. We thank W. van Westrenen and an anonymous reviewer for their helpful comments.
PY - 2009
Y1 - 2009
N2 - We determined experimentally the Nernst distribution coefficient Diopx-melt = ciorthopyroxene/cimelt between orthopyroxene and anhydrous silicate melt for trace elements i in the system Na2O-CaO-MgO-Al2O3-SiO2 (NCMAS) along the dry model lherzolite solidus from 1.1 GPa/1,230 °C up to 3.2 GPa/1,535 °C in a piston cylinder apparatus. Major and trace element composition of melt and orthopyroxene were determined with a combination of electron microprobe and ion probe analyses. We provide partitioning data for trace elements Li, Be, B, K, Sc, Ti, V, Cr, Co, Ni, Rb, Sr, Y, Zr, Nb, Cs, Ba, La, Ce, Sm, Nd, Yb, Lu, Hf, Ta, Pb, U, and Th. The melts were chosen to be boninitic at 1.1 and 2.0 GPa, picritic at 2.3 GPa and komatiitic at 2.7 and 3.2 GPa. Orthopyroxene is Tschermakitic with 8 mol% Mg-Tschermaks MgAl[AlSiO6] at 1.1 GPa while at higher pressure it has 18-20 mol%. The rare earth elements show a continuous, significant increase in compatibility with decreasing ionic radius from DLaopx-melt ∼ 0.0008 to DLuopx-melt ∼ 0.15. For the high-field-strength elements compatibility increases from D Thopx-melt ∼ 0.001 through DNbopx-melt ∼ 0.0015, DUopx-melt ∼ 0.002, DTaopx-melt ∼ 0.005, DZropx-melt ∼ 0.02 and DHfopx-melt ∼ 0.04 to D Tiopx-melt ∼ 0.14. From mathematical and graphical fits we determined best-fit values for D0M1, D0M2, r0M1, r0M2, E0M1, and E0M2 for the two different M sites in orthopyroxene according to the lattice strain model and calculated the intracrystalline distribution between M1 and M2. Our data indicate extreme intracrystalline fractionation for most elements in orthopyroxene; for the divalent cations DiM2-M1 varies by three orders of magnitude between DCoM2-M1 = 0.00098-0.00919 and DBaM2-M1 = 2.3-28. Trivalent cations Al and Cr almost exclusively substitute on M1 while the other trivalent cations substitute on M2; DLaM2-M1 reaches extreme values between 6.5 × 107 and 1.4 × 1016. Tetravalent cations Ti, Hf, and Zr almost exclusively substitute on M1 while U and Th exclusively substitute on M2. Our new comprehensive data set can be used for polybaric-polythermal melting models along the Earth's mantle solidus.
AB - We determined experimentally the Nernst distribution coefficient Diopx-melt = ciorthopyroxene/cimelt between orthopyroxene and anhydrous silicate melt for trace elements i in the system Na2O-CaO-MgO-Al2O3-SiO2 (NCMAS) along the dry model lherzolite solidus from 1.1 GPa/1,230 °C up to 3.2 GPa/1,535 °C in a piston cylinder apparatus. Major and trace element composition of melt and orthopyroxene were determined with a combination of electron microprobe and ion probe analyses. We provide partitioning data for trace elements Li, Be, B, K, Sc, Ti, V, Cr, Co, Ni, Rb, Sr, Y, Zr, Nb, Cs, Ba, La, Ce, Sm, Nd, Yb, Lu, Hf, Ta, Pb, U, and Th. The melts were chosen to be boninitic at 1.1 and 2.0 GPa, picritic at 2.3 GPa and komatiitic at 2.7 and 3.2 GPa. Orthopyroxene is Tschermakitic with 8 mol% Mg-Tschermaks MgAl[AlSiO6] at 1.1 GPa while at higher pressure it has 18-20 mol%. The rare earth elements show a continuous, significant increase in compatibility with decreasing ionic radius from DLaopx-melt ∼ 0.0008 to DLuopx-melt ∼ 0.15. For the high-field-strength elements compatibility increases from D Thopx-melt ∼ 0.001 through DNbopx-melt ∼ 0.0015, DUopx-melt ∼ 0.002, DTaopx-melt ∼ 0.005, DZropx-melt ∼ 0.02 and DHfopx-melt ∼ 0.04 to D Tiopx-melt ∼ 0.14. From mathematical and graphical fits we determined best-fit values for D0M1, D0M2, r0M1, r0M2, E0M1, and E0M2 for the two different M sites in orthopyroxene according to the lattice strain model and calculated the intracrystalline distribution between M1 and M2. Our data indicate extreme intracrystalline fractionation for most elements in orthopyroxene; for the divalent cations DiM2-M1 varies by three orders of magnitude between DCoM2-M1 = 0.00098-0.00919 and DBaM2-M1 = 2.3-28. Trivalent cations Al and Cr almost exclusively substitute on M1 while the other trivalent cations substitute on M2; DLaM2-M1 reaches extreme values between 6.5 × 107 and 1.4 × 1016. Tetravalent cations Ti, Hf, and Zr almost exclusively substitute on M1 while U and Th exclusively substitute on M2. Our new comprehensive data set can be used for polybaric-polythermal melting models along the Earth's mantle solidus.
KW - Experimental determination
KW - Iherzolite-orthopyroxen distribution coefficients
KW - Intracrystalline distribution
UR - http://www.scopus.com/inward/record.url?scp=60449108676&partnerID=8YFLogxK
U2 - 10.1007/s00410-008-0346-5
DO - 10.1007/s00410-008-0346-5
M3 - Article
SN - 0010-7999
VL - 157
SP - 473
EP - 490
JO - Contributions to Mineralogy and Petrology
JF - Contributions to Mineralogy and Petrology
IS - 4
ER -