High-temperature study of octahedral cation exchange in olivine by neutron powder diffraction

C. M.B. Henderson; K. S. Knight; S. A.T. Redfern; B. J. Wood

doi:10.1126/science.271.5256.1713

High-temperature study of octahedral cation exchange in olivine by neutron powder diffraction

C. M.B. Henderson^*, K. S. Knight, S. A.T. Redfern, B. J. Wood

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

62 Citations (Scopus)

Abstract

Time-of-flight, neutron powder diffraction to 1000°C provides precise octahedral site occupancies and intersite distribution coefficients for MnMgSiO₄ and MnFeSiO₄ olivines. Intersite exchange occurs in minutes down to 500°C. Equilibrium distribution coefficients show that manganese ordering into the larger octahedral site decreases with increasing temperature. Exchange energies are 15.7 and 10.1 kilojoules per mole for magnesium-manganese and iron-manganese, respectively. Distribution coefficients deduced for FeMgSiO₄ olivine suggest an exchange energy of 4.8 kilojoules per mole. Intersite exchange energies are consistent with diffusion coefficients in the order iron > magnesium > manganese. Geothermometry based on magnesium-manganese and iron-manganese exchange may be possible only for samples equilibrated below 500°C.

Original language	English
Pages (from-to)	1713-1715
Number of pages	3
Journal	Science
Volume	271
Issue number	5256
DOIs	https://doi.org/10.1126/science.271.5256.1713
Publication status	Published - Mar 22 1996
Externally published	Yes

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title = "High-temperature study of octahedral cation exchange in olivine by neutron powder diffraction",

abstract = "Time-of-flight, neutron powder diffraction to 1000°C provides precise octahedral site occupancies and intersite distribution coefficients for MnMgSiO4 and MnFeSiO4 olivines. Intersite exchange occurs in minutes down to 500°C. Equilibrium distribution coefficients show that manganese ordering into the larger octahedral site decreases with increasing temperature. Exchange energies are 15.7 and 10.1 kilojoules per mole for magnesium-manganese and iron-manganese, respectively. Distribution coefficients deduced for FeMgSiO4 olivine suggest an exchange energy of 4.8 kilojoules per mole. Intersite exchange energies are consistent with diffusion coefficients in the order iron > magnesium > manganese. Geothermometry based on magnesium-manganese and iron-manganese exchange may be possible only for samples equilibrated below 500°C.",

author = "Henderson, {C. M.B.} and Knight, {K. S.} and Redfern, {S. A.T.} and Wood, {B. J.}",

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doi = "10.1126/science.271.5256.1713",

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T1 - High-temperature study of octahedral cation exchange in olivine by neutron powder diffraction

AU - Henderson, C. M.B.

AU - Knight, K. S.

AU - Redfern, S. A.T.

AU - Wood, B. J.

PY - 1996/3/22

Y1 - 1996/3/22

N2 - Time-of-flight, neutron powder diffraction to 1000°C provides precise octahedral site occupancies and intersite distribution coefficients for MnMgSiO4 and MnFeSiO4 olivines. Intersite exchange occurs in minutes down to 500°C. Equilibrium distribution coefficients show that manganese ordering into the larger octahedral site decreases with increasing temperature. Exchange energies are 15.7 and 10.1 kilojoules per mole for magnesium-manganese and iron-manganese, respectively. Distribution coefficients deduced for FeMgSiO4 olivine suggest an exchange energy of 4.8 kilojoules per mole. Intersite exchange energies are consistent with diffusion coefficients in the order iron > magnesium > manganese. Geothermometry based on magnesium-manganese and iron-manganese exchange may be possible only for samples equilibrated below 500°C.

AB - Time-of-flight, neutron powder diffraction to 1000°C provides precise octahedral site occupancies and intersite distribution coefficients for MnMgSiO4 and MnFeSiO4 olivines. Intersite exchange occurs in minutes down to 500°C. Equilibrium distribution coefficients show that manganese ordering into the larger octahedral site decreases with increasing temperature. Exchange energies are 15.7 and 10.1 kilojoules per mole for magnesium-manganese and iron-manganese, respectively. Distribution coefficients deduced for FeMgSiO4 olivine suggest an exchange energy of 4.8 kilojoules per mole. Intersite exchange energies are consistent with diffusion coefficients in the order iron > magnesium > manganese. Geothermometry based on magnesium-manganese and iron-manganese exchange may be possible only for samples equilibrated below 500°C.

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High-temperature study of octahedral cation exchange in olivine by neutron powder diffraction

Abstract

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