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Open AccessArticle

Petrologic and Minerochemical Trends of Acapulcoites, Winonaites and Lodranites: New Evidence from Image Analysis and EMPA Investigations

1
Dipartimento di Scienze della Terra, Università degli Studi di Firenze, Via La Pira 4, 50121 Florence, Italy
2
Dipartimento di Chimica, Università degli Studi di Firenze, Via della Lastruccia 3, 50019 Sesto Fiorentino, Italy
3
Consorzio INSTM, Via Giusti 9, 50121 Florence, Italy
*
Author to whom correspondence should be addressed.
These authors contributed equally to this work.
This paper is an extended version of our paper published in the 42nd Lunar and Planetary Science Conference, The Woodlands, TX, USA, 7–11 March 2011.
Academic Editor: Jesus Martinez-Frias
Geosciences 2015, 5(3), 222-242; https://doi.org/10.3390/geosciences5030222
Received: 1 April 2015 / Revised: 17 June 2015 / Accepted: 23 June 2015 / Published: 2 July 2015
A comprehensive classification of primitive achondrites is difficult due to the high compositional and textural variability and the low number of samples available. Besides oxygen isotopic analysis, other minerochemical and textural parameters may provide a useful tool to solve taxonomic and genetic problems related to these achondrites. The results of a detailed modal, textural and minerochemical analysis of a set of primitive achondrites are presented and compared with literature data. All the samples show an extremely variable modal composition among both silicate and opaque phases. A general trend of troilite depletion vs. silicate fraction enrichment has been observed, with differences among coarse-grained and fine-grained meteorites. In regard to the mineral chemistry, olivine shows marked differences between the acapulcoite-lodranite and winonaite groups, while a compositional equilibrium between matrix and chondrules for both groups, probably due to the scarce influence of metamorphic grade on this phase, was observed. The analysis of Cr and Mn in clinopyroxene revealed two separate clusters for the acapulcoite/lodranite and winonaite groups, while the analysis of the reduction state highlighted three separate clusters. An estimate of equilibrium temperatures for the acapulcoite-lodranite and winonaite groups is provided. Finally, proposals regarding the genetic processes of these groups are discussed. View Full-Text
Keywords: primitive achondrites; acapulcoite; lodranites; winonaites; X-ray maps primitive achondrites; acapulcoite; lodranites; winonaites; X-ray maps
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Cecchi, V.M.; Caporali, S. Petrologic and Minerochemical Trends of Acapulcoites, Winonaites and Lodranites: New Evidence from Image Analysis and EMPA Investigations. Geosciences 2015, 5, 222-242.

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