A SYSTEMATIC CLASSIFICATION OF METEORITES
PART IV

DIOGENITES

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

DIOGENITES (7 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)

6. POLYMICT   dunite ± harzburgite ± orthopyroxenite ± eucrite (<10 vol%)

    (e.g. LEW 88008, ALH 85015, NWA 1239, NWA 1648, NWA 2923, NWA 4473)

7. GENOMICT   all clasts fractionally related

    (e.g. EETA79002)

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.

The diogenite classification ternary diagram shown below is from Wittke et al. (2011) 74th Meteorit Soc. Mtg., #5223.

© 1997–2013 by David Weir