Universität zu Köln

Hezel, Dominik C., Wilden, Johanna S., Becker, Daniel, Steinbach, Sonja ORCID: 0000-0001-8392-5807, Wombacher, Frank ORCID: 0000-0002-0755-8918 and Harak, Markus (2018). Fe isotope composition of bulk chondrules from Murchison (CM2): Constraints for parent body alteration, nebula processes and chondrule-matrix complementarity. Earth Planet. Sci. Lett., 490. S. 31 - 40. AMSTERDAM: ELSEVIER SCIENCE BV. ISSN 1385-013X

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Abstract

Chondrules are a major constituent of primitive meteorites. The formation of chondrules is one of the most elusive problems in cosmochemistry. We use Fe isotope compositions of chondrules and bulk chondrites to constrain the conditions of chondrule formation. Iron isotope compositions of bulk chondrules are so far only known from few studies on CV and some ordinary chondrites. We studied 37 chondrules from the CM chondrite Murchison. This is particularly challenging, as CM chondrites contain the smallest chondrules of all chondrite groups, except for CH chondrites. Bulk chondrules have delta Fe-56 between -0.62 and +0.24%o relative to the IRMM-014 standard. Bulk Murchison has as all chondrites a (delta Fe-56 of 0.009'00 within error. The delta Fe-56 distribution of the Murchison chondrule population is continuous and close to normal. The width of the delta Fe-56 distribution is narrower than that of the Allende chondrule population. Opaque modal abundances in Murchison chondrules is in about 67% of the chondrules close to 0 vol.%, and in 33% typically up to 6.5 vol.%. Chondrule Al/Mg and Fe/Mg ratios are sub-chondritic, while bulk Murchison has chondritic ratios. We suggest that the variable bulk chondrule Fe isotope compositions were established during evaporation and recondensation prior to accretion in the Murchison parent body. This range in isotope composition was likely reduced during aqueous alteration on the parent body. Murchison has a chondritic Fe isotope composition and a number of chondritic element ratios. Chondrules, however, have variable Fe isotope compositions and chondrules and matrix have complementary Al/Mg and Fe/Mg ratios. In combination, this supports the idea that chondrules and matrix formed from a single reservoir and were then accreted in the parent body. The formation in a single region also explains the compositional distribution of the chondrule population in Murchison. (C) 2018 Elsevier B.V. All rights reserved.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Hezel, Dominik C. UNSPECIFIED UNSPECIFIED UNSPECIFIED Wilden, Johanna S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Becker, Daniel UNSPECIFIED UNSPECIFIED UNSPECIFIED Steinbach, Sonja UNSPECIFIED orcid.org/0000-0001-8392-5807 UNSPECIFIED Wombacher, Frank UNSPECIFIED orcid.org/0000-0002-0755-8918 UNSPECIFIED Harak, Markus UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-186432
DOI:	10.1016/j.epsl.2018.03.013
Journal or Publication Title:	Earth Planet. Sci. Lett.
Volume:	490
Page Range:	S. 31 - 40
Date:	2018
Publisher:	ELSEVIER SCIENCE BV
Place of Publication:	AMSTERDAM
ISSN:	1385-013X
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language STONY COSMIC SPHERULES; EARLY SOLAR NEBULA; CARBONACEOUS CHONDRITES; CV CHONDRITES; IRON; FRACTIONATION; ORIGIN; COMPONENTS; SYSTEM; METEORITES Multiple languages Geochemistry & Geophysics Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/18643