Meteoritic petrology versus genetics: Toward a unified binomial taxonomy

Meteoritic petrology versus genetics: Toward a unified binomial taxonomy

Schematic diagram of the genetics and petrology of current meteorite groups with known C/NC affinities (eg, Kleine et al., 2020; Weisberg et al., 2006). The x-coordinate is arbitrary and the proximity between two groups does not imply genetic relationships unless they are explicitly enclosed in a higher-level common group (filled lower-level groups, whose names are written in the vertical direction, are supposed to extend to the range of the entire class that includes it; are Fill in the gaps with a dotted line). Hypothetical assignments of chondrites and acapulcoites to matrix-rich chondrites are discussed in the chondrite section. Here, a clan of ordinary chondrites (OC) is distinguished from the more extensive O group, which consists of dissimilar meteorites (eg, Iron IIE); Same for EC vs. E and CC vs. C (see Chondrites section). I am showing in purple dotted an unknown Robin Ma (2021) HED-MES-PMG-IIIAB “superclass”, which is a group in our language. , hence the impossibility of defining a true hierarchy among them except for locally nested groups. While only definite groups are shown comprehensively, any anomalous meteorite must land somewhere in this diagram, in its class, and a more or less broadly defined group (eg, C, NC, O, E) and thus lends itself to the limit Lower than the standard classification profile. As an illustration, the “eucrite-type” meteorites Ibitira and NWA 011 were plotted in the same class of basaltic achondrite as bona fide eucrites but marked from them on the group axis as “NC-an” and “C-an,” respectively. The abbreviations are the same as those in Table 1. (The colored figure can be seen at wileyonlinelibrary.com.)

The current meteorite taxonomy, the result of two centuries of research and meteorite tradition, intertwines with synthetic and genetic terms in a less than consistent manner, with some taxa (such as shergottites) representing diverse lithologies from a single putative main body while others (such as pallasites) accommodate relatively similar organisms of origins different to the solar system.

It is also difficult to empirically determine the familiar concept of a group as representative of a single, primary primary body. It is proposed that the classification become explicitly binary throughout the meteorite spectrum, with categories denoting the primary rock types identified by rocks, while groups retain a genetic meaning, but are no longer associated with any assumption as to the number of parent bodies represented.

Thus, the classification of the meteorite would include both a class and a group, in a two-dimensional manner similar to the way Van Schmeus and Wood separated primary and secondary properties in chondrites. Since the groups will not, initially, differ fundamentally from those currently used de facto, the taxonomic treatment of ordinary meteorites, the category of which will not bring new information, hardly changes.

However, categories combined with high- or low-level groups would provide a unified network for characterizing stony and/or unusual or theoretically anomalous meteorites (which make up the majority of the meteorite parent bodies represented) for example, with respect to the carbon/noncarbon split. In the long term, mergers of genetically related groups, more systematic manipulation of lithology mixtures, and chondrite/chondrite transition can simplify the nomenclature.

Emmanuel Jaquet

Comments: 21 pages, 4 numbers
Topics: Earth and Planetary Astrophysics (astro-ph.EP)
Cited as follows: arXiv: 2209.07377 [astro-ph.EP] (or arXiv: 2209.07377v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2209.07377
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Journal reference: Jacquet E. (2022). Meteoritics and Planets 57: 1774-1794
Related DOI:
https://doi.org/10.1111/maps.13896
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Submission date
Who: Emmanuel Jacquet
[v1] Thursday, September 15, 2022 15:44:09 UTC (1,181 KB)
https://arxiv.org/abs/2209.07377
Astrobiology, astronomy, astrochemistry

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