A SYSTEMATIC CLASSIFICATION OF METEORITES
PART IV

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

DIOGENITES

HED (Vesta) material of ultramafic composition (olivine+orthopyroxene ≥90 vol%)
Classification Based on IUGS Taxonomy

DIOGENITES (6 subclasses known based on modal mineralogy)
1. ORTHOPYROXENITIC   ≥90 vol% orthopyroxene
    (e.g. QUE 99050, Tatahouine, NWA 1821, NWA 3329, Johnstown, Bilanga)
2. OLIVINE–ORTHOPYROXENITIC   orthopyroxene + 10–40 vol% olivine
    (e.g. GRA 98108, ALHA77256, LEW 88679, NWA 5405, NWA 5312)
3. HARZBURGITIC   >40 vol% olivine
    (e.g. NWA 1459, 1877 and pairings, NWA 4223, NWA 5480, NWA 6157, EETA79002, MIL 07001)
4. DUNITIC   ≥90 vol% olivine
    (e.g. MIL 03443, NWA 2968)
5. NORITIC   orthopyroxene + <5 vol% olivine + >10 vol% plagioclase
    (e.g. NWA 2824, NWA 5315, NWA 6928, NWA 8000, NWA 8367, NWA 8744, NWA 10268, NWA 10388)
6. POLYMICT   dunite ± harzburgite ± orthopyroxenite ± eucrite (<10 vol%)
    (e.g. LEW 88008, ALH 85015, NWA 1239, NWA 1648, NWA 4473, NWA 6945 [w/ noritic clasts])

standby for diogenite triangle plot
Diagram credit: Irving et al., 47th LPSC, #2264 (2016)

According to Beck and McSween (2010), diogenites represent two separate ultramafic lithologies formed by fractional crystallization 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 brecciation and mixing, sometimes forming polymict diogenites containing olivine with two pyroxenes.

The diogenite classification scheme and data used on this page is 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 diogenite classification ternary diagram shown below is from Wittke et al. (2011) 74th Meteorit Soc. Mtg., #5223.



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


You must collect things for reasons you don't yet understand.
Daniel J. Boorstin – Librarian of Congress



© 1997–2017 by David Weir