Multicomponent cubic oxide exsolution in synthetic basalts

Temperature dependence and implications for magnetic properties

Julie A. Bowles, Lisa Tatsumi-Petrochilos, Julia E. Hammer, Stefanie Brachfeld

Research output: Contribution to journalArticleResearchpeer-review

8 Citations (Scopus)

Abstract

Although the compositional unmixing of cubic-structured iron oxides has profound effects on the magnetic properties of rocks that contain them, a basic understanding of the kinetics and thermodynamics of this process has not been achieved in experimental studies due to sluggish reaction rates in binary oxide phases. Exploiting the fact that many natural Fe-oxides contain multiple additional cations, including Ti, Mg and Al, we perform novel "forward" laboratory experiments in which cubic-cubic phase exsolution proceeds from initially homogeneous multicomponent oxides. A variety of Fe-Ti-Mg-Al cubic iron oxides were nucleated and grown in synthetic, multicomponent basalt under different fO2 environments, and annealed at temperatures ranging from 590-790°C for up to 88 days. Fine-scale lamellar intergrowths of Fe-Ti-Al-Mg oxides, interpreted to represent cubic phase exsolution, were observed in seven samples, one that was synthesized and annealed at approximately constant fO2 (the quartz-fayalite- magnetite, or QFM, buffer) and six that were synthesized at very oxidizing conditions (∼QFM+6 log units) and then annealed at moderately oxidizing (∼QFM) conditions. Results demonstrate that the consolute temperature of the multicomponent system is significantly higher than anneal temperatures and Curie temperatures, suggesting that samples that undergo this type of exsolution can carry a total thermal remanent magnetization. Exsolved samples are characterized by a dramatic increase in magnetization and coercivity, and a shift in Curie temperature(s), confirming predictions that this type of exsolution exerts strong control on the strength and stability of magnetization.

Original languageEnglish
Article numberB03202
JournalJournal of Geophysical Research: Solid Earth
Volume117
Issue number3
DOIs
StatePublished - 1 Mar 2012

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exsolution
magnetic property
basalt
Oxides
Magnetic properties
oxide
magnetic properties
Magnetization
temperature dependence
oxides
Curie temperature
iron oxides
magnetization
temperature
iron oxide
Ferrosoferric Oxide
fayalite
Temperature
Quartz
Coercive force

Cite this

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abstract = "Although the compositional unmixing of cubic-structured iron oxides has profound effects on the magnetic properties of rocks that contain them, a basic understanding of the kinetics and thermodynamics of this process has not been achieved in experimental studies due to sluggish reaction rates in binary oxide phases. Exploiting the fact that many natural Fe-oxides contain multiple additional cations, including Ti, Mg and Al, we perform novel {"}forward{"} laboratory experiments in which cubic-cubic phase exsolution proceeds from initially homogeneous multicomponent oxides. A variety of Fe-Ti-Mg-Al cubic iron oxides were nucleated and grown in synthetic, multicomponent basalt under different fO2 environments, and annealed at temperatures ranging from 590-790°C for up to 88 days. Fine-scale lamellar intergrowths of Fe-Ti-Al-Mg oxides, interpreted to represent cubic phase exsolution, were observed in seven samples, one that was synthesized and annealed at approximately constant fO2 (the quartz-fayalite- magnetite, or QFM, buffer) and six that were synthesized at very oxidizing conditions (∼QFM+6 log units) and then annealed at moderately oxidizing (∼QFM) conditions. Results demonstrate that the consolute temperature of the multicomponent system is significantly higher than anneal temperatures and Curie temperatures, suggesting that samples that undergo this type of exsolution can carry a total thermal remanent magnetization. Exsolved samples are characterized by a dramatic increase in magnetization and coercivity, and a shift in Curie temperature(s), confirming predictions that this type of exsolution exerts strong control on the strength and stability of magnetization.",
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Multicomponent cubic oxide exsolution in synthetic basalts : Temperature dependence and implications for magnetic properties. / Bowles, Julie A.; Tatsumi-Petrochilos, Lisa; Hammer, Julia E.; Brachfeld, Stefanie.

In: Journal of Geophysical Research: Solid Earth, Vol. 117, No. 3, B03202, 01.03.2012.

Research output: Contribution to journalArticleResearchpeer-review

TY - JOUR

T1 - Multicomponent cubic oxide exsolution in synthetic basalts

T2 - Temperature dependence and implications for magnetic properties

AU - Bowles, Julie A.

AU - Tatsumi-Petrochilos, Lisa

AU - Hammer, Julia E.

AU - Brachfeld, Stefanie

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N2 - Although the compositional unmixing of cubic-structured iron oxides has profound effects on the magnetic properties of rocks that contain them, a basic understanding of the kinetics and thermodynamics of this process has not been achieved in experimental studies due to sluggish reaction rates in binary oxide phases. Exploiting the fact that many natural Fe-oxides contain multiple additional cations, including Ti, Mg and Al, we perform novel "forward" laboratory experiments in which cubic-cubic phase exsolution proceeds from initially homogeneous multicomponent oxides. A variety of Fe-Ti-Mg-Al cubic iron oxides were nucleated and grown in synthetic, multicomponent basalt under different fO2 environments, and annealed at temperatures ranging from 590-790°C for up to 88 days. Fine-scale lamellar intergrowths of Fe-Ti-Al-Mg oxides, interpreted to represent cubic phase exsolution, were observed in seven samples, one that was synthesized and annealed at approximately constant fO2 (the quartz-fayalite- magnetite, or QFM, buffer) and six that were synthesized at very oxidizing conditions (∼QFM+6 log units) and then annealed at moderately oxidizing (∼QFM) conditions. Results demonstrate that the consolute temperature of the multicomponent system is significantly higher than anneal temperatures and Curie temperatures, suggesting that samples that undergo this type of exsolution can carry a total thermal remanent magnetization. Exsolved samples are characterized by a dramatic increase in magnetization and coercivity, and a shift in Curie temperature(s), confirming predictions that this type of exsolution exerts strong control on the strength and stability of magnetization.

AB - Although the compositional unmixing of cubic-structured iron oxides has profound effects on the magnetic properties of rocks that contain them, a basic understanding of the kinetics and thermodynamics of this process has not been achieved in experimental studies due to sluggish reaction rates in binary oxide phases. Exploiting the fact that many natural Fe-oxides contain multiple additional cations, including Ti, Mg and Al, we perform novel "forward" laboratory experiments in which cubic-cubic phase exsolution proceeds from initially homogeneous multicomponent oxides. A variety of Fe-Ti-Mg-Al cubic iron oxides were nucleated and grown in synthetic, multicomponent basalt under different fO2 environments, and annealed at temperatures ranging from 590-790°C for up to 88 days. Fine-scale lamellar intergrowths of Fe-Ti-Al-Mg oxides, interpreted to represent cubic phase exsolution, were observed in seven samples, one that was synthesized and annealed at approximately constant fO2 (the quartz-fayalite- magnetite, or QFM, buffer) and six that were synthesized at very oxidizing conditions (∼QFM+6 log units) and then annealed at moderately oxidizing (∼QFM) conditions. Results demonstrate that the consolute temperature of the multicomponent system is significantly higher than anneal temperatures and Curie temperatures, suggesting that samples that undergo this type of exsolution can carry a total thermal remanent magnetization. Exsolved samples are characterized by a dramatic increase in magnetization and coercivity, and a shift in Curie temperature(s), confirming predictions that this type of exsolution exerts strong control on the strength and stability of magnetization.

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M3 - Article

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JO - Journal of Geophysical Research: Solid Earth

JF - Journal of Geophysical Research: Solid Earth

SN - 2169-9313

IS - 3

M1 - B03202

ER -