Diffusivity of strontium, neodymium, and lead in natural rhyolite melt at 1.0 GPa

Chemical diffusivities approximating tracer diffusivities of Sr, Nd, and Pb have been measured in a natural rhyolite melt at 1.0 GPa and temperatures from 1000 to 1450°C using the diffusion couple technique. Diffusivities for all three elements were determined under nominally anhydrous conditions. L...

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Autores principales: Perez, W.A., Dunn, T.
Formato: JOUR
Materias:
chemical diffusivity
isotopic exchange
lead
magma chamber
neodymium
rhyolite melt
strontium
Acceso en línea:http://hdl.handle.net/20.500.12110/paper_00167037_v60_n8_p1387_Perez
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Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
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spelling todo:paper_00167037_v60_n8_p1387_Perez2023-10-03T14:14:36Z Diffusivity of strontium, neodymium, and lead in natural rhyolite melt at 1.0 GPa Perez, W.A. Dunn, T. chemical diffusivity isotopic exchange lead magma chamber neodymium rhyolite melt strontium Chemical diffusivities approximating tracer diffusivities of Sr, Nd, and Pb have been measured in a natural rhyolite melt at 1.0 GPa and temperatures from 1000 to 1450°C using the diffusion couple technique. Diffusivities for all three elements were determined under nominally anhydrous conditions. Lead diffusivities were also determined at ∼1 and 2.5 wt% dissolved H 2 O in the melt. The results are described by the following Arrhenius equations (D in m 2 /s, activation energy in J/mol, T in Kelvin): D (Sr,dry) = 1.58 × 10 -3 e -(264200/RT) D (Nd,dry) = 1.28 × 10 -2 e -(330200/RT) D (Pb,dry) = 1.92 × 10 -7 e -(148400/RT) D (Pb,∼1%) = 1.18 × 10 -7 e -(131700/RT) D (Pb,∼2.5%) = 2.18 × 10 -9 e -(73600/RT) . The results are consistent to within an order of magnitude with previously reported Sr, Nd, and Pb tracer diffusivities. Under anhydrous conditions, the relative magnitudes of the diffusion coefficients are D Sr ≈ D Pb > D Nd . D Nd determined in this work is similar to previously reported D Si . The implication of these results is that Pb and Sr diffusion-controlled isotopic and chemical exchange can occur at a faster rate than major element chemical exchange, but that Nd exchange occurs at about the same rate as major element exchange. The consequences of this process are illustrated with a model of isotopic exchange in a basaltic-granitic, double-diffusive, convecting magma chamber. The diffusivity of Pb increases with increasing dissolved water more than that of Si increases suggesting that, at least for Pb, isotopic homogenization also occurs faster than chemical homogenization under hydrous conditions. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_00167037_v60_n8_p1387_Perez
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic chemical diffusivity
isotopic exchange
lead
magma chamber
neodymium
rhyolite melt
strontium
spellingShingle chemical diffusivity
isotopic exchange
lead
magma chamber
neodymium
rhyolite melt
strontium
Perez, W.A.
Dunn, T.
Diffusivity of strontium, neodymium, and lead in natural rhyolite melt at 1.0 GPa
topic_facet chemical diffusivity
isotopic exchange
lead
magma chamber
neodymium
rhyolite melt
strontium
description Chemical diffusivities approximating tracer diffusivities of Sr, Nd, and Pb have been measured in a natural rhyolite melt at 1.0 GPa and temperatures from 1000 to 1450°C using the diffusion couple technique. Diffusivities for all three elements were determined under nominally anhydrous conditions. Lead diffusivities were also determined at ∼1 and 2.5 wt% dissolved H 2 O in the melt. The results are described by the following Arrhenius equations (D in m 2 /s, activation energy in J/mol, T in Kelvin): D (Sr,dry) = 1.58 × 10 -3 e -(264200/RT) D (Nd,dry) = 1.28 × 10 -2 e -(330200/RT) D (Pb,dry) = 1.92 × 10 -7 e -(148400/RT) D (Pb,∼1%) = 1.18 × 10 -7 e -(131700/RT) D (Pb,∼2.5%) = 2.18 × 10 -9 e -(73600/RT) . The results are consistent to within an order of magnitude with previously reported Sr, Nd, and Pb tracer diffusivities. Under anhydrous conditions, the relative magnitudes of the diffusion coefficients are D Sr ≈ D Pb > D Nd . D Nd determined in this work is similar to previously reported D Si . The implication of these results is that Pb and Sr diffusion-controlled isotopic and chemical exchange can occur at a faster rate than major element chemical exchange, but that Nd exchange occurs at about the same rate as major element exchange. The consequences of this process are illustrated with a model of isotopic exchange in a basaltic-granitic, double-diffusive, convecting magma chamber. The diffusivity of Pb increases with increasing dissolved water more than that of Si increases suggesting that, at least for Pb, isotopic homogenization also occurs faster than chemical homogenization under hydrous conditions.
format JOUR
author Perez, W.A.
Dunn, T.
author_facet Perez, W.A.
Dunn, T.
author_sort Perez, W.A.
title Diffusivity of strontium, neodymium, and lead in natural rhyolite melt at 1.0 GPa
title_short Diffusivity of strontium, neodymium, and lead in natural rhyolite melt at 1.0 GPa
title_full Diffusivity of strontium, neodymium, and lead in natural rhyolite melt at 1.0 GPa
title_fullStr Diffusivity of strontium, neodymium, and lead in natural rhyolite melt at 1.0 GPa
title_full_unstemmed Diffusivity of strontium, neodymium, and lead in natural rhyolite melt at 1.0 GPa
title_sort diffusivity of strontium, neodymium, and lead in natural rhyolite melt at 1.0 gpa
url http://hdl.handle.net/20.500.12110/paper_00167037_v60_n8_p1387_Perez
work_keys_str_mv AT perezwa diffusivityofstrontiumneodymiumandleadinnaturalrhyolitemeltat10gpa
AT dunnt diffusivityofstrontiumneodymiumandleadinnaturalrhyolitemeltat10gpa
_version_ 1807318871727669248

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