Opaque phases in type-II chondrules from CR2 chondrites: Implications for CR parent body formation

Devin Schrader, Harold C. Connolly, Dante S. Lauretta

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

We report the results of a detailed study of sulfide-bearing opaque assemblages from the MAC 87320, EET 92011, and Renazzo CR carbonaceous chondrites. The objectives of this study are to (1) characterize sulfide and associated phases within CR2 chondrites; (2) determine the petrographic relationship between sulfides, metals, and chondrules; (3) constrain the history of type-II chondrules; (4) ascertain the environments in which type-II chondrules formed and were altered; and (5) unravel the formation and alteration history of the CR parent body as recorded in sulfide-bearing assemblages. Sulfide-bearing opaque assemblages occur primarily within type-II (FeO-rich) chondrules. The sulfide assemblages are concentrated near the chondrule edges. Assemblages in MAC 87320 are composed of troilite, phosphate, and Ni-rich metal. EET 92011 contains assemblages composed of pentlandite, troilite, and Ni-rich metal. The assemblages in Renazzo contain tochilinite, magnetite, troilite, pentlandite, and phosphate. In all of the assemblages in Renazzo the tochilinite is fine grained and intimately mixed with troilite, pentlandite, or magnetite. Opaque assemblages in CR chondrites record a complex history that includes both high- and low-temperature processes. The morphology and composition of sulfides in CR2 chondrites suggests that the sulfide-bearing assemblages originally formed in gas-solid reactions in the nebula at temperatures above the Fe-FeS eutectic (988 °C). Many of the assemblages were subsequently aqueously altered on the CR-chondrite parent body to various degrees at temperatures from ∼50 to 200 °C. We combine these observations and interpretations to provide a detailed model of the history of the CR parent body.

Original languageEnglish (US)
Pages (from-to)6124-6140
Number of pages17
JournalGeochimica et Cosmochimica Acta
Volume72
Issue number24
DOIs
StatePublished - Dec 15 2008

Fingerprint

chondrule
parent body
Sulfides
chondrite
Bearings (structural)
sulfide
troilite
pentlandite
Ferrosoferric Oxide
Metals
history
magnetite
metal
Phosphates
phosphate
Temperature
carbonaceous chondrite
Eutectics
Gases
temperature

ASJC Scopus subject areas

  • Geochemistry and Petrology

Cite this

Opaque phases in type-II chondrules from CR2 chondrites : Implications for CR parent body formation. / Schrader, Devin; Connolly, Harold C.; Lauretta, Dante S.

In: Geochimica et Cosmochimica Acta, Vol. 72, No. 24, 15.12.2008, p. 6124-6140.

Research output: Contribution to journalArticle

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