Di¡usive fractionation of trace elements during production and transport of melt in Earth’s upper mantle
We have developed a numerical model to investigate the importance of diffusive chemical fractionation during production and transport of melt in Earth’s upper mantle. The model incorporates new experimental data on the diffusion rates of rare earth elements (REE) in high-Ca pyroxene [Van Orman et al...
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ftciteseerx:oai:CiteSeerX.psu:10.1.1.522.1761 2023-05-15T13:39:53+02:00 Di¡usive fractionation of trace elements during production and transport of melt in Earth’s upper mantle James A. Van Orman A Timothy L. Grove A Nobumichi Shimizu B The Pennsylvania State University CiteSeerX Archives 2002 application/pdf http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.522.1761 http://geology.case.edu/~vanorman/pdf/VanOrman_EPSL_2002.pdf en eng http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.522.1761 http://geology.case.edu/~vanorman/pdf/VanOrman_EPSL_2002.pdf Metadata may be used without restrictions as long as the oai identifier remains attached to it. http://geology.case.edu/~vanorman/pdf/VanOrman_EPSL_2002.pdf text 2002 ftciteseerx 2016-01-08T10:11:35Z We have developed a numerical model to investigate the importance of diffusive chemical fractionation during production and transport of melt in Earth’s upper mantle. The model incorporates new experimental data on the diffusion rates of rare earth elements (REE) in high-Ca pyroxene [Van Orman et al., Contrib. Mineral. Petrol. 141 (2001) 687^703] and pyrope garnet [Van Orman et al., Contrib. Mineral. Petrol., in press], including the dependence of diffusivity on temperature, pressure and ionic radius. We find that diffusion exerts an important control on REE fractionation under conditions typical of melting beneath slow spreading centers, provided that grain radii are V0.5 mm or greater. When partitioning is diffusion-limited, REE are fractionated less efficiently than under equilibrium conditions, and this effect becomes more pronounced as the melting rate, grain size, and efficiency of melt segregation increase. Data for the light REE in abyssal peridotite clinopyroxene (cpx) grains from the slow spreading America^ Antarctic and Southwest Indian ridge systems are better explained by melting models that allow for diffusive exchange than by models that assume complete solid^melt equilibration. The data are best fit by models in which the initial cpx grain radii are V2^3 mm and melt extraction is very efficient (near fractional). Diffusion is likely to play a strong role in REE fractionation during intergranular melt transport in the upper mantle. Complete equilibrium between solid and melt requires very sluggish melt transport, with ascent rates on the order of a few centimeters per Text Antarc* Antarctic Unknown Antarctic Indian |
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We have developed a numerical model to investigate the importance of diffusive chemical fractionation during production and transport of melt in Earth’s upper mantle. The model incorporates new experimental data on the diffusion rates of rare earth elements (REE) in high-Ca pyroxene [Van Orman et al., Contrib. Mineral. Petrol. 141 (2001) 687^703] and pyrope garnet [Van Orman et al., Contrib. Mineral. Petrol., in press], including the dependence of diffusivity on temperature, pressure and ionic radius. We find that diffusion exerts an important control on REE fractionation under conditions typical of melting beneath slow spreading centers, provided that grain radii are V0.5 mm or greater. When partitioning is diffusion-limited, REE are fractionated less efficiently than under equilibrium conditions, and this effect becomes more pronounced as the melting rate, grain size, and efficiency of melt segregation increase. Data for the light REE in abyssal peridotite clinopyroxene (cpx) grains from the slow spreading America^ Antarctic and Southwest Indian ridge systems are better explained by melting models that allow for diffusive exchange than by models that assume complete solid^melt equilibration. The data are best fit by models in which the initial cpx grain radii are V2^3 mm and melt extraction is very efficient (near fractional). Diffusion is likely to play a strong role in REE fractionation during intergranular melt transport in the upper mantle. Complete equilibrium between solid and melt requires very sluggish melt transport, with ascent rates on the order of a few centimeters per |
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The Pennsylvania State University CiteSeerX Archives |
format |
Text |
author |
James A. Van Orman A Timothy L. Grove A Nobumichi Shimizu B |
spellingShingle |
James A. Van Orman A Timothy L. Grove A Nobumichi Shimizu B Di¡usive fractionation of trace elements during production and transport of melt in Earth’s upper mantle |
author_facet |
James A. Van Orman A Timothy L. Grove A Nobumichi Shimizu B |
author_sort |
James A. Van Orman A |
title |
Di¡usive fractionation of trace elements during production and transport of melt in Earth’s upper mantle |
title_short |
Di¡usive fractionation of trace elements during production and transport of melt in Earth’s upper mantle |
title_full |
Di¡usive fractionation of trace elements during production and transport of melt in Earth’s upper mantle |
title_fullStr |
Di¡usive fractionation of trace elements during production and transport of melt in Earth’s upper mantle |
title_full_unstemmed |
Di¡usive fractionation of trace elements during production and transport of melt in Earth’s upper mantle |
title_sort |
di¡usive fractionation of trace elements during production and transport of melt in earth’s upper mantle |
publishDate |
2002 |
url |
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.522.1761 http://geology.case.edu/~vanorman/pdf/VanOrman_EPSL_2002.pdf |
geographic |
Antarctic Indian |
geographic_facet |
Antarctic Indian |
genre |
Antarc* Antarctic |
genre_facet |
Antarc* Antarctic |
op_source |
http://geology.case.edu/~vanorman/pdf/VanOrman_EPSL_2002.pdf |
op_relation |
http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.522.1761 http://geology.case.edu/~vanorman/pdf/VanOrman_EPSL_2002.pdf |
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Metadata may be used without restrictions as long as the oai identifier remains attached to it. |
_version_ |
1766125908469481472 |