Thermodynamic constraints on the formation conditions of winonaites and silicate-bearing IAB irons

Gretchen K. Benedix, Dante Lauretta, Timothy J. McCoy

Research output: Contribution to journalArticle

45 Citations (Scopus)

Abstract

Silicate inclusions in IAB irons and related winonaite meteorites have textures, mineralogies and mineral chemistries that indicate a complex formation history of heating, followed by brecciation and metamorphism. Using olivine-orthopyroxene-chromite assemblages in five IAB iron silicate inclusions (Caddo County, Campo del Cielo, Copiapo, Lueders, and Udei Station) and one winonaite (Winona), we calculated closure temperatures and oxygen fugacities for these meteorites. Calculated olivine-chromite Fe-Mg exchange temperatures are compared to two-pyroxene temperatures. Olivine-chromite closure temperatures range from ∼590°C to ∼700°C, while two-pyroxene temperatures range from ∼900°C to ∼1200°C. Oxygen fugacities of these meteorites, determined for the first time in this study, range from 2.3 to 3.2 log units below the Fe-FeO buffer and define a line between the Fe-FeO and Cr-Cr2O3 buffers. Highly variable temperatures were experienced by these rocks on the hand sample, and sometimes even the thin section, scale consistent with the idea that the winonaite-IAB iron parent body experienced collisional fragmentation and reassembly after peak temperatures were reached. Although modest reduction likely occurred during cooling, the oxygen fugacities and mineral compositions recorded at peak metamorphic temperatures suggest that the chondritic precursor for this parent body was initially more reduced than ordinary chondrites.

Original languageEnglish (US)
Pages (from-to)5123-5131
Number of pages9
JournalGeochimica et Cosmochimica Acta
Volume69
Issue number21
DOIs
StatePublished - Nov 1 2005

Fingerprint

Bearings (structural)
Silicates
silicate
thermodynamics
Thermodynamics
Iron
iron
chromite
Meteorites
fugacity
Chromite
meteorite
closure temperature
olivine
temperature
parent body
pyroxene
Temperature
oxygen
Oxygen

ASJC Scopus subject areas

  • Geochemistry and Petrology

Cite this

Thermodynamic constraints on the formation conditions of winonaites and silicate-bearing IAB irons. / Benedix, Gretchen K.; Lauretta, Dante; McCoy, Timothy J.

In: Geochimica et Cosmochimica Acta, Vol. 69, No. 21, 01.11.2005, p. 5123-5131.

Research output: Contribution to journalArticle

@article{42a850fd2d1b41d3b6b37c9223ac2b1d,
title = "Thermodynamic constraints on the formation conditions of winonaites and silicate-bearing IAB irons",
abstract = "Silicate inclusions in IAB irons and related winonaite meteorites have textures, mineralogies and mineral chemistries that indicate a complex formation history of heating, followed by brecciation and metamorphism. Using olivine-orthopyroxene-chromite assemblages in five IAB iron silicate inclusions (Caddo County, Campo del Cielo, Copiapo, Lueders, and Udei Station) and one winonaite (Winona), we calculated closure temperatures and oxygen fugacities for these meteorites. Calculated olivine-chromite Fe-Mg exchange temperatures are compared to two-pyroxene temperatures. Olivine-chromite closure temperatures range from ∼590°C to ∼700°C, while two-pyroxene temperatures range from ∼900°C to ∼1200°C. Oxygen fugacities of these meteorites, determined for the first time in this study, range from 2.3 to 3.2 log units below the Fe-FeO buffer and define a line between the Fe-FeO and Cr-Cr2O3 buffers. Highly variable temperatures were experienced by these rocks on the hand sample, and sometimes even the thin section, scale consistent with the idea that the winonaite-IAB iron parent body experienced collisional fragmentation and reassembly after peak temperatures were reached. Although modest reduction likely occurred during cooling, the oxygen fugacities and mineral compositions recorded at peak metamorphic temperatures suggest that the chondritic precursor for this parent body was initially more reduced than ordinary chondrites.",
author = "Benedix, {Gretchen K.} and Dante Lauretta and McCoy, {Timothy J.}",
year = "2005",
month = "11",
day = "1",
doi = "10.1016/j.gca.2005.03.048",
language = "English (US)",
volume = "69",
pages = "5123--5131",
journal = "Geochmica et Cosmochimica Acta",
issn = "0016-7037",
publisher = "Elsevier Limited",
number = "21",

}

TY - JOUR

T1 - Thermodynamic constraints on the formation conditions of winonaites and silicate-bearing IAB irons

AU - Benedix, Gretchen K.

AU - Lauretta, Dante

AU - McCoy, Timothy J.

PY - 2005/11/1

Y1 - 2005/11/1

N2 - Silicate inclusions in IAB irons and related winonaite meteorites have textures, mineralogies and mineral chemistries that indicate a complex formation history of heating, followed by brecciation and metamorphism. Using olivine-orthopyroxene-chromite assemblages in five IAB iron silicate inclusions (Caddo County, Campo del Cielo, Copiapo, Lueders, and Udei Station) and one winonaite (Winona), we calculated closure temperatures and oxygen fugacities for these meteorites. Calculated olivine-chromite Fe-Mg exchange temperatures are compared to two-pyroxene temperatures. Olivine-chromite closure temperatures range from ∼590°C to ∼700°C, while two-pyroxene temperatures range from ∼900°C to ∼1200°C. Oxygen fugacities of these meteorites, determined for the first time in this study, range from 2.3 to 3.2 log units below the Fe-FeO buffer and define a line between the Fe-FeO and Cr-Cr2O3 buffers. Highly variable temperatures were experienced by these rocks on the hand sample, and sometimes even the thin section, scale consistent with the idea that the winonaite-IAB iron parent body experienced collisional fragmentation and reassembly after peak temperatures were reached. Although modest reduction likely occurred during cooling, the oxygen fugacities and mineral compositions recorded at peak metamorphic temperatures suggest that the chondritic precursor for this parent body was initially more reduced than ordinary chondrites.

AB - Silicate inclusions in IAB irons and related winonaite meteorites have textures, mineralogies and mineral chemistries that indicate a complex formation history of heating, followed by brecciation and metamorphism. Using olivine-orthopyroxene-chromite assemblages in five IAB iron silicate inclusions (Caddo County, Campo del Cielo, Copiapo, Lueders, and Udei Station) and one winonaite (Winona), we calculated closure temperatures and oxygen fugacities for these meteorites. Calculated olivine-chromite Fe-Mg exchange temperatures are compared to two-pyroxene temperatures. Olivine-chromite closure temperatures range from ∼590°C to ∼700°C, while two-pyroxene temperatures range from ∼900°C to ∼1200°C. Oxygen fugacities of these meteorites, determined for the first time in this study, range from 2.3 to 3.2 log units below the Fe-FeO buffer and define a line between the Fe-FeO and Cr-Cr2O3 buffers. Highly variable temperatures were experienced by these rocks on the hand sample, and sometimes even the thin section, scale consistent with the idea that the winonaite-IAB iron parent body experienced collisional fragmentation and reassembly after peak temperatures were reached. Although modest reduction likely occurred during cooling, the oxygen fugacities and mineral compositions recorded at peak metamorphic temperatures suggest that the chondritic precursor for this parent body was initially more reduced than ordinary chondrites.

UR - http://www.scopus.com/inward/record.url?scp=28344455306&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=28344455306&partnerID=8YFLogxK

U2 - 10.1016/j.gca.2005.03.048

DO - 10.1016/j.gca.2005.03.048

M3 - Article

AN - SCOPUS:28344455306

VL - 69

SP - 5123

EP - 5131

JO - Geochmica et Cosmochimica Acta

JF - Geochmica et Cosmochimica Acta

SN - 0016-7037

IS - 21

ER -