Systematics: Diogenites – Classification Based on IUGS Taxonomy

PART I: CHONDRITES, METACHONDRITES
PART II: PRIMITIVE ACHONDRITES, ACHONDRITES, STONY-IRONS, IRONS
PART III: MARTIAN METEORITES—GEOCHEMICAL CLASSIFICATION
PART V: ENSTATITE CHONDRITES—SUBGROUP CLASSIFICATION

DIOGENITES

HED (VestaThird largest and fourth brightest asteroid; it was discovered in 1807 by Heinrich Olbers and named for the ancient Roman goddess of the hearth. 4 Vesta has a basaltic surface composition and an average density not much less than that of Mars. Evidently lava once flowed here indicating that the) material of ultramaficTerm used for silicate minerals with cations predominantly Mg and/or Fe. Mafic minerals are dominated by plagioclase and pyroxene, and also contain smaller amounts of olivine. composition (olivine+orthopyroxeneOrthorhombic, low-Ca pyroxene common in chondrites. Its compositional range runs from all Mg-rich enstatite, MgSiO3 to Fe-rich ferrosilite, FeSiO3. These end-members form an almost complete solid solution where Mg2+ substitutes for Fe2+ up to about 90 mol. % and Ca substitutes no more than ~5 mol. % (higher Ca2+ contents occur ≥90 vol%)
Classification Based on IUGS Taxonomy

Diagram credit: Irving et al., 47th LPSC, #2264 (2016)

According to Beck and McSween (2010), diogenites represent two separate ultramafic lithologies formed by fractional crystallizationA crystallization process in which minerals crystallizing from a magma are isolated from contact with the liquid. It is a key process in the formation of igneous rocks during the process of magmatic differentiation. Also known as crystal fractionation. in multiple plutons. Of these two lithologies, one consists of olivine + magnesian orthopyroxene, and the other consists of ferroan orthopyroxene. It is thought that these two lithologies occur in varying amounts among the different diogenites as a result of brecciationThe formation of a breccia through a process by which rock fragments of of various types are recemented or fused together. and mixing, sometimes forming polymict diogenites containing olivine with two pyroxenes.

The diogeniteDiogenites belong to the evolved achondrite HED group that also includes howardites and eucrites. They are named after the Greek philosopher Diogenes of Apollonia, of the 5th century BCE, who was the first to suggest that meteorites come from outer space (a realization forgotten for over 2,000 years). They are classification scheme and data used on this page are adapted from Beck and McSween Jr., MAPS, vol. 45, #5, pp. 850-872 (2010). An extension of their scheme was suggested by Wittke et al. (2011). The diogeniteDiogenites belong to the evolved achondrite HED group that also includes howardites and eucrites. They are named after the Greek philosopher Diogenes of Apollonia, of the 5th century BCE, who was the first to suggest that meteorites come from outer space (a realization forgotten for over 2,000 years). They are classification ternary diagram shown below is from Wittke et al. 74th MetSoc, #5223 (2011).

PART I: CHONDRITES, METACHONDRITES
PART II: PRIMITIVE ACHONDRITES, ACHONDRITES, STONY-IRONS, IRONS
PART III: MARTIAN METEORITES—GEOCHEMICAL CLASSIFICATION
PART V: ENSTATITE CHONDRITES—SUBGROUP CLASSIFICATION

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