Differentiation history of the mesosiderite parent body

Constraints from trace elements and manganese-chromium isotope systematics in Vaca Muerta silicate clasts

Meenakshi Wadhwa, A. Shukolyukov, A. M. Davis, G. W. Lugmair, D. W. Mittlefehldt

Research output: Contribution to journalArticle

29 Citations (Scopus)

Abstract

We report here the results of a study of trace element microdistributions and 53Mn-53Cr systematics in several basaltic and orthopyroxenitic clasts from the Vaca Muerta mesosiderite. Ion microprobe analyses of selected trace and minor element abundances in minerals of the silicate clasts indicate that, following igneous crystallization, these clasts underwent extensive metamorphic equilibration that resulted in intra- and inter-grain redistribution of elements. There is also evidence in the elemental microdistributions that these clasts were subsequently affected to varying degrees by alteration resulting from redox reactions involving the indigenous silicates and externally derived reducing agents (such as phosphorus, derived from the mesosiderite metal) at the time of metal-silicate mixing. Furthermore, our results suggest that the varying degrees of alteration by redox reactions recorded in the different clasts were most likely facilitated by different degrees of remelting induced by heating during the metal-silicate mixing event. After taking into account the effects of these postmagmatic secondary processes, comparison of the trace and minor element concentrations and distributions in minerals of basaltic and orthopyroxenitic clasts with those of noncumulate eucrites and diogenites, respectively, suggests that the primary igneous petrogenesis, including parent magma and source compositions, of Vaca Muerta silicates were similar to those of achondritic meteorites of the Howardite-Eucrite-Diogenite (HED) association. Internal 53Mn-53Cr isochrons obtained for two basaltic (pebble 16 and 4679) and two orthopyroxenitic (4659 and 4670) clasts show that chromium isotopes are equilibrated within each clast. Nevertheless, just as for noncumulate eucrites and diogenites, 53Cr excesses in whole-rock samples of the basaltic clasts (∼1.01 ε in pebble 16; ∼1.07 ε in 4679) are significantly higher than in the orthopyroxene-rich clasts (∼0.62 ε in 4659; ∼0.53 ε in 4670). As in the case of the HED parent body, this suggests that Mn/Cr fractionation in the parent body of the Vaca Muerta silicate clasts occurred very early in the history of the solar system, when 53Mn was still extant. However, the slope of the 53Mn-53Cr isochron defined by the whole-rock samples of Vaca Muerta clasts (corresponding to a 53Mn/55Mn ratio of 3.3 ± 0.6 × 10-6) is distinctly lower than that defined by the HED whole-rock samples (corresponding to a 53Mn/55Mn ratio of 4.7 ± 0.5 × 10-6), indicating that the global Mn/Cr fractionation event that established mantle source reservoirs on the parent body of the Vaca Muerta silicate clasts occurred ∼2 Ma after a similar event on the HED parent body.

Original languageEnglish (US)
Pages (from-to)5047-5069
Number of pages23
JournalGeochimica et Cosmochimica Acta
Volume67
Issue number24
DOIs
StatePublished - Dec 15 2003
Externally publishedYes

Fingerprint

Chromium Isotopes
mesosiderite
Silicates
parent body
Trace Elements
Manganese
clast
chromium
manganese
silicate
trace element
isotope
eucrite
history
diogenite
howardite
Redox reactions
Metals
Rocks
Fractionation

ASJC Scopus subject areas

  • Geochemistry and Petrology

Cite this

Differentiation history of the mesosiderite parent body : Constraints from trace elements and manganese-chromium isotope systematics in Vaca Muerta silicate clasts. / Wadhwa, Meenakshi; Shukolyukov, A.; Davis, A. M.; Lugmair, G. W.; Mittlefehldt, D. W.

In: Geochimica et Cosmochimica Acta, Vol. 67, No. 24, 15.12.2003, p. 5047-5069.

Research output: Contribution to journalArticle

@article{0b704ba7cb4c447495ccf7e279ccd7c3,
title = "Differentiation history of the mesosiderite parent body: Constraints from trace elements and manganese-chromium isotope systematics in Vaca Muerta silicate clasts",
abstract = "We report here the results of a study of trace element microdistributions and 53Mn-53Cr systematics in several basaltic and orthopyroxenitic clasts from the Vaca Muerta mesosiderite. Ion microprobe analyses of selected trace and minor element abundances in minerals of the silicate clasts indicate that, following igneous crystallization, these clasts underwent extensive metamorphic equilibration that resulted in intra- and inter-grain redistribution of elements. There is also evidence in the elemental microdistributions that these clasts were subsequently affected to varying degrees by alteration resulting from redox reactions involving the indigenous silicates and externally derived reducing agents (such as phosphorus, derived from the mesosiderite metal) at the time of metal-silicate mixing. Furthermore, our results suggest that the varying degrees of alteration by redox reactions recorded in the different clasts were most likely facilitated by different degrees of remelting induced by heating during the metal-silicate mixing event. After taking into account the effects of these postmagmatic secondary processes, comparison of the trace and minor element concentrations and distributions in minerals of basaltic and orthopyroxenitic clasts with those of noncumulate eucrites and diogenites, respectively, suggests that the primary igneous petrogenesis, including parent magma and source compositions, of Vaca Muerta silicates were similar to those of achondritic meteorites of the Howardite-Eucrite-Diogenite (HED) association. Internal 53Mn-53Cr isochrons obtained for two basaltic (pebble 16 and 4679) and two orthopyroxenitic (4659 and 4670) clasts show that chromium isotopes are equilibrated within each clast. Nevertheless, just as for noncumulate eucrites and diogenites, 53Cr excesses in whole-rock samples of the basaltic clasts (∼1.01 ε in pebble 16; ∼1.07 ε in 4679) are significantly higher than in the orthopyroxene-rich clasts (∼0.62 ε in 4659; ∼0.53 ε in 4670). As in the case of the HED parent body, this suggests that Mn/Cr fractionation in the parent body of the Vaca Muerta silicate clasts occurred very early in the history of the solar system, when 53Mn was still extant. However, the slope of the 53Mn-53Cr isochron defined by the whole-rock samples of Vaca Muerta clasts (corresponding to a 53Mn/55Mn ratio of 3.3 ± 0.6 × 10-6) is distinctly lower than that defined by the HED whole-rock samples (corresponding to a 53Mn/55Mn ratio of 4.7 ± 0.5 × 10-6), indicating that the global Mn/Cr fractionation event that established mantle source reservoirs on the parent body of the Vaca Muerta silicate clasts occurred ∼2 Ma after a similar event on the HED parent body.",
author = "Meenakshi Wadhwa and A. Shukolyukov and Davis, {A. M.} and Lugmair, {G. W.} and Mittlefehldt, {D. W.}",
year = "2003",
month = "12",
day = "15",
doi = "10.1016/j.gca.2003.08.005",
language = "English (US)",
volume = "67",
pages = "5047--5069",
journal = "Geochmica et Cosmochimica Acta",
issn = "0016-7037",
publisher = "Elsevier Limited",
number = "24",

}

TY - JOUR

T1 - Differentiation history of the mesosiderite parent body

T2 - Constraints from trace elements and manganese-chromium isotope systematics in Vaca Muerta silicate clasts

AU - Wadhwa, Meenakshi

AU - Shukolyukov, A.

AU - Davis, A. M.

AU - Lugmair, G. W.

AU - Mittlefehldt, D. W.

PY - 2003/12/15

Y1 - 2003/12/15

N2 - We report here the results of a study of trace element microdistributions and 53Mn-53Cr systematics in several basaltic and orthopyroxenitic clasts from the Vaca Muerta mesosiderite. Ion microprobe analyses of selected trace and minor element abundances in minerals of the silicate clasts indicate that, following igneous crystallization, these clasts underwent extensive metamorphic equilibration that resulted in intra- and inter-grain redistribution of elements. There is also evidence in the elemental microdistributions that these clasts were subsequently affected to varying degrees by alteration resulting from redox reactions involving the indigenous silicates and externally derived reducing agents (such as phosphorus, derived from the mesosiderite metal) at the time of metal-silicate mixing. Furthermore, our results suggest that the varying degrees of alteration by redox reactions recorded in the different clasts were most likely facilitated by different degrees of remelting induced by heating during the metal-silicate mixing event. After taking into account the effects of these postmagmatic secondary processes, comparison of the trace and minor element concentrations and distributions in minerals of basaltic and orthopyroxenitic clasts with those of noncumulate eucrites and diogenites, respectively, suggests that the primary igneous petrogenesis, including parent magma and source compositions, of Vaca Muerta silicates were similar to those of achondritic meteorites of the Howardite-Eucrite-Diogenite (HED) association. Internal 53Mn-53Cr isochrons obtained for two basaltic (pebble 16 and 4679) and two orthopyroxenitic (4659 and 4670) clasts show that chromium isotopes are equilibrated within each clast. Nevertheless, just as for noncumulate eucrites and diogenites, 53Cr excesses in whole-rock samples of the basaltic clasts (∼1.01 ε in pebble 16; ∼1.07 ε in 4679) are significantly higher than in the orthopyroxene-rich clasts (∼0.62 ε in 4659; ∼0.53 ε in 4670). As in the case of the HED parent body, this suggests that Mn/Cr fractionation in the parent body of the Vaca Muerta silicate clasts occurred very early in the history of the solar system, when 53Mn was still extant. However, the slope of the 53Mn-53Cr isochron defined by the whole-rock samples of Vaca Muerta clasts (corresponding to a 53Mn/55Mn ratio of 3.3 ± 0.6 × 10-6) is distinctly lower than that defined by the HED whole-rock samples (corresponding to a 53Mn/55Mn ratio of 4.7 ± 0.5 × 10-6), indicating that the global Mn/Cr fractionation event that established mantle source reservoirs on the parent body of the Vaca Muerta silicate clasts occurred ∼2 Ma after a similar event on the HED parent body.

AB - We report here the results of a study of trace element microdistributions and 53Mn-53Cr systematics in several basaltic and orthopyroxenitic clasts from the Vaca Muerta mesosiderite. Ion microprobe analyses of selected trace and minor element abundances in minerals of the silicate clasts indicate that, following igneous crystallization, these clasts underwent extensive metamorphic equilibration that resulted in intra- and inter-grain redistribution of elements. There is also evidence in the elemental microdistributions that these clasts were subsequently affected to varying degrees by alteration resulting from redox reactions involving the indigenous silicates and externally derived reducing agents (such as phosphorus, derived from the mesosiderite metal) at the time of metal-silicate mixing. Furthermore, our results suggest that the varying degrees of alteration by redox reactions recorded in the different clasts were most likely facilitated by different degrees of remelting induced by heating during the metal-silicate mixing event. After taking into account the effects of these postmagmatic secondary processes, comparison of the trace and minor element concentrations and distributions in minerals of basaltic and orthopyroxenitic clasts with those of noncumulate eucrites and diogenites, respectively, suggests that the primary igneous petrogenesis, including parent magma and source compositions, of Vaca Muerta silicates were similar to those of achondritic meteorites of the Howardite-Eucrite-Diogenite (HED) association. Internal 53Mn-53Cr isochrons obtained for two basaltic (pebble 16 and 4679) and two orthopyroxenitic (4659 and 4670) clasts show that chromium isotopes are equilibrated within each clast. Nevertheless, just as for noncumulate eucrites and diogenites, 53Cr excesses in whole-rock samples of the basaltic clasts (∼1.01 ε in pebble 16; ∼1.07 ε in 4679) are significantly higher than in the orthopyroxene-rich clasts (∼0.62 ε in 4659; ∼0.53 ε in 4670). As in the case of the HED parent body, this suggests that Mn/Cr fractionation in the parent body of the Vaca Muerta silicate clasts occurred very early in the history of the solar system, when 53Mn was still extant. However, the slope of the 53Mn-53Cr isochron defined by the whole-rock samples of Vaca Muerta clasts (corresponding to a 53Mn/55Mn ratio of 3.3 ± 0.6 × 10-6) is distinctly lower than that defined by the HED whole-rock samples (corresponding to a 53Mn/55Mn ratio of 4.7 ± 0.5 × 10-6), indicating that the global Mn/Cr fractionation event that established mantle source reservoirs on the parent body of the Vaca Muerta silicate clasts occurred ∼2 Ma after a similar event on the HED parent body.

UR - http://www.scopus.com/inward/record.url?scp=0346335721&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0346335721&partnerID=8YFLogxK

U2 - 10.1016/j.gca.2003.08.005

DO - 10.1016/j.gca.2003.08.005

M3 - Article

VL - 67

SP - 5047

EP - 5069

JO - Geochmica et Cosmochimica Acta

JF - Geochmica et Cosmochimica Acta

SN - 0016-7037

IS - 24

ER -