The formation and alteration of the Renazzo-like carbonaceous chondrites III

Toward understanding the genesis of ferromagnesian chondrules

Devin Schrader, Harold C. Connolly, Dante S. Lauretta, Thomas J. Zega, Jemma Davidson, Kenneth J. Domanik

Research output: Contribution to journalArticle

24 Citations (Scopus)

Abstract

To better understand the formation conditions of ferromagnesian chondrules from the Renazzo-like carbonaceous (CR) chondrites, a systematic study of 210 chondrules from 15 CR chondrites was conducted. The texture and composition of silicate and opaque minerals from each observed FeO-rich (type II) chondrule, and a representative number of FeO-poor (type I) chondrules, were studied to build a substantial and self-consistent data set. The average abundances and standard deviations of Cr2O3 in FeO-rich olivine phenocrysts are consistent with previous work that the CR chondrites are among the least thermally altered samples from the early solar system. Type II chondrules from the CR chondrites formed under highly variable conditions (e.g., precursor composition, redox conditions, cooling rate), with each chondrule recording a distinct igneous history. The opaque minerals within type II chondrules are consistent with formation during chondrule melting and cooling, starting as S- and Ni-rich liquids at 988-1350 °C, then cooling to form monosulfide solid solution (mss) that crystallized around olivine/pyroxene phenocrysts. During cooling, Fe,Ni-metal crystallized from the S- and Ni-rich liquid, and upon further cooling mss decomposed into pentlandite and pyrrhotite, with pentlandite exsolving from mss at 400-600 °C. The composition, texture, and inferred formation temperature of pentlandite within chondrules studied here is inconsistent with formation via aqueous alteration. However, some opaque minerals (Fe,Ni-metal versus magnetite and panethite) present in type II chondrules are a proxy for the degree of whole-rock aqueous alteration. The texture and composition of sulfide-bearing opaque minerals in Graves Nunataks 06100 and Grosvenor Mountains 03116 suggest that they are the most thermally altered CR chondrites.

Original languageEnglish (US)
Pages (from-to)15-50
Number of pages36
JournalMeteoritics and Planetary Science
Volume50
Issue number1
DOIs
StatePublished - Jan 1 2015

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chondrule
carbonaceous chondrites
carbonaceous chondrite
pentlandite
cooling
solid solution
minerals
solid solutions
textures
texture
mineral
olivine
nunataks
pyrrhotite
liquid
metal
redox conditions
liquids
mountains
solar system

ASJC Scopus subject areas

  • Geophysics
  • Space and Planetary Science

Cite this

The formation and alteration of the Renazzo-like carbonaceous chondrites III : Toward understanding the genesis of ferromagnesian chondrules. / Schrader, Devin; Connolly, Harold C.; Lauretta, Dante S.; Zega, Thomas J.; Davidson, Jemma; Domanik, Kenneth J.

In: Meteoritics and Planetary Science, Vol. 50, No. 1, 01.01.2015, p. 15-50.

Research output: Contribution to journalArticle

Schrader, Devin ; Connolly, Harold C. ; Lauretta, Dante S. ; Zega, Thomas J. ; Davidson, Jemma ; Domanik, Kenneth J. / The formation and alteration of the Renazzo-like carbonaceous chondrites III : Toward understanding the genesis of ferromagnesian chondrules. In: Meteoritics and Planetary Science. 2015 ; Vol. 50, No. 1. pp. 15-50.
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