TY - JOUR
T1 - Magma differentiation fractionates Mo isotope ratios
T2 - evidence from the Kos Plateau Tuff (Aegean Arc)
AU - Vögelin, Andrea Regula
AU - Pettke, Thomas
AU - Greber, Nicolas D.
AU - von Niederhaeusern, Brigitte
AU - Naegler, Thomas F.
PY - 2014/3
Y1 - 2014/3
N2 - We investigated high temperature Mo isotope fractionation in a hydrous supra-subduction volcano-plutonic system (Kos, Aegean Arc, Greece) in order to address the debate on the δ98/95Mo variability of the continental crust. In this igneous system, where differentiation is interpreted to be dominated by fractional crystallization, bulk rock data from olivine basalt to dacite show δ98/95Mo ratios increasing from +0.3 to +0.6‰ along with Mo concentrations increasing from 0.8 to 4.1μgg-1. Data for hornblende and biotite mineral separates reveal the extraction of light Mo into crystallizing silicates, with minimum partition coefficients between hornblende-silicate melt and biotite-silicate melt of 0.6 and 0.4 δ98/95Mo, respectively.Our data document significant Mo isotope fractionation at magmatic temperatures, hence, the igneous contribution to continental runoff is variable, besides probable source-related variability. Based on these results and published data an average continental δ98/95Mo of +0.3 to +0.4‰ can be derived. This signature corresponds more closely to the average of published data of dissolved Mo loads of large rivers than previous estimates and is consistent with an upper limit of δ98/95Mo=0.4‰ of the Earth's upper crust as derived from the analysis of molybdenites.
AB - We investigated high temperature Mo isotope fractionation in a hydrous supra-subduction volcano-plutonic system (Kos, Aegean Arc, Greece) in order to address the debate on the δ98/95Mo variability of the continental crust. In this igneous system, where differentiation is interpreted to be dominated by fractional crystallization, bulk rock data from olivine basalt to dacite show δ98/95Mo ratios increasing from +0.3 to +0.6‰ along with Mo concentrations increasing from 0.8 to 4.1μgg-1. Data for hornblende and biotite mineral separates reveal the extraction of light Mo into crystallizing silicates, with minimum partition coefficients between hornblende-silicate melt and biotite-silicate melt of 0.6 and 0.4 δ98/95Mo, respectively.Our data document significant Mo isotope fractionation at magmatic temperatures, hence, the igneous contribution to continental runoff is variable, besides probable source-related variability. Based on these results and published data an average continental δ98/95Mo of +0.3 to +0.4‰ can be derived. This signature corresponds more closely to the average of published data of dissolved Mo loads of large rivers than previous estimates and is consistent with an upper limit of δ98/95Mo=0.4‰ of the Earth's upper crust as derived from the analysis of molybdenites.
U2 - 10.1016/j.lithos.2013.12.016
DO - 10.1016/j.lithos.2013.12.016
M3 - Journal article
SN - 0024-4937
VL - 190-191
SP - 440
EP - 448
JO - Lithos
JF - Lithos
ER -