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A unique high Mn/Fe microgabbro in the Parnallee (LL3) ordinary chondrite - Nebular mixture or planetary differentiate from a previously unrecognized planetary body?We studied a unique microgabbro fragment from the Parnallee (LL3) unequilibrated ordinary chondrite. The fragment, which was originally identified by its ophitic to sub-ophitic texture, exhibits features characteristic of lunar and terrestrial tholeiitic basalts (i.e., extreme compositional zoning in clinopyroxene (Wo10En65Fs25 to Wo15En2FS83), a multiply saturated major element composition similar to mid-ocean ridge basalt with 3.1 wt pct Na2O and 0.15 wt pct K2O, and uniformly enriched rare earth elements (c. 10 x C1). A high bulk MnO/FeO ratio (0.064) distinguishes the microgabbro from other basaltic rocks and suggests the precursor material formed or reached equilibrium in a reducing environment. However, the absence of Fe metal and the extreme enrichment of FeO (up to 40 wt pct), in late crystallizing pyroxferroite, requires the last crystallization event to have occurred in a relatively oxidizing environment. We suggest the microgabbro formed by partial melting in a planetary body after removal of metallic Fe.
Document ID
19930027675
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Kennedy, A. K.
(California Inst. of Technology Pasadena, United States)
Hutchison, R.
(Natural History Museum London, United Kingdom)
Hutcheon, I. D.
(California Inst. of Technology Pasadena, United States)
Agrell, S. O.
(Cambridge Univ. United Kingdom)
Date Acquired
August 15, 2013
Publication Date
September 1, 1992
Publication Information
Publication: Earth and Planetary Science Letters
Volume: 113
Issue: 2-Jan
ISSN: 0012-821X
Subject Category
Lunar And Planetary Exploration
Accession Number
93A11672
Funding Number(s)
CONTRACT_GRANT: NAG9-43
Distribution Limits
Public
Copyright
Other

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