A SYSTEMATIC CLASSIFICATION OF METEORITES
PART V

PART I: CHONDRITES, METACHONDRITES
PART II: PRIMITIVE ACHONDRITES, ACHONDRITES, STONY-IRONS, IRONS
PART III: MARTIAN METEORITES—GEOCHEMICAL CLASSIFICATION
PART IV: DIOGENITES—IUGS TAXONOMY

ENSTATITE (E) CHONDRITES

Subgroup classification after Weyrauch et al., MAPS, vol. 53, #3, pp. 394–415 (2018)
'Chemical variations of sulfides and metal in enstatite chondrites—Introduction of a new classification scheme'

ENSTATITE CHONDRITES
(4 subgroups plus ungrouped/anomalous members, based on mineral and chemical data [see below])
ELa
ELa3 (e.g. AhS MS-189, MAC 88136 [3.8/3.9], MAC 02747 [3/4], QUE 94594)
ELa4 (e.g. DaG 734, Grein 002 [4/5])
ELa5 (e.g. AhS MS-201, TIL 91714)
ELa6 (e.g. Atlanta, Daniel’s Kuil, Hvittis, Khairpur, Neuschwanstein, NWA 3134, Pillistfer, Sahara 99456, Yilmia)
ELa7/impact-melt phase (e.g. Ilafegh 009 [7/MR])
ELb
ELb3 (e.g. AhS MS-17 [3/4], AhS MS-164 [3/4], AhS MS-200 [3/4], AhS MS-MU-002 [3/4], AhS MS-MU-003 [3/4])
ELb4 (e.g. Y-793246)
ELb5 (e.g. AhS MS-7 [5/6], AhS MS-196, RKPA80259)
ELb6 (e.g. AhS MS-52, AhS MS-79, AhS MS-150, AhS MS-159, AhS MS-172, AhS MS-174, AhS MS-D, AhS MS-MU-007, EET 90102, LEW 87119)
ELb7/impact-melt phase (no sample classified)
EHa
EHa3 (e.g. AhS MS-14, ALH 84206, GRO 95517, MIL 07028, Parsa, Qingzhen, Sah 97096 [3.1–3.4])
EHa4 (e.g. EET 87746, EET 96135 [4/5], Indarch, MET 00636, PCA 82518, Y-74370)
EHa5 (e.g. St. Mark's, QUE 93372)
EHa6 (no sample classified)
EHa7/impact melt phase (e.g. LAP 02225 [IMR])
EHb
EHb3 (no sample classified)
EHb4 (e.g. Adhi Kot [or IMB])
EHb5 (e.g. AhS MS-13, AhS MS-155, AhS MS-163, AhS MS-192, LEW 88180, Saint-Sauveur [IMB])
EHb6 (e.g. Y-8404 and pairings [or IMB/MR], Y-980211, Y-980223)
EHb7/impact melt phase (e.g. Abee [IMB])

ENSTATITE CHONDRITES—NOT YET CLASSIFIED BY SUBGROUP
EL
EL3 (e.g. Kaidun IV, NWA 305, NWA 3132, NWA 2965 and pairings [3/6 IMB], QUE 93351)
EL4 (e.g. DaG 1031, FRO 03005, HaH 317, QUE 94368)
EL5 (e.g. Adrar Bous, NWA 1222, Tanezrouft 031)
EL6 (e.g. Eagle, Forrest 033)
EL7/impact-melt phase (e.g. Happy Canyon [MR], Y-980524 [IMB])
EH
EH3 (e.g. Galim (b) [IMB], Hadley Rille [IM])
EH4 (e.g. Bethune [4/5], Dhofar 1015, LAP 031220, Y-791810)
EH5 (e.g. A-881475, Kaidun-III, Oudiyat Sbaa)
EH6 (e.g. MIL 090846, NWA 6363, NWA 7976, NWA 8513 [IMB])
EH7/impact melt phase (e.g. Itqiy [Meta-EH-anom or partial melt residue], NWA 2526 [similar to Itqiy], NWA 7324 [MR], NWA 10237 [MR], QUE 94204 [7], Y-82189 [IM], Y-8414 [IM])
UNGROUPED E CHONDRITES
E-ung (e.g. LAP 031220 [4], LEW 87223 [3-anom], NWA 974 [6], PCA 91020 [3-anom; poss. rel. to LEW 87223], QUE 94204 [7], Y-793225 [6-anom])

Weyrauch et al. (2018) analyzed the mineral and chemical data from 80 enstatite chondrites representing both EH and EL groups and spanning the full range of petrologic types for each group. They found that a bimodality exists in each of these groups with respect to both the Cr content in troilite and the Fe concentration in niningerite and alabandite (endmembers of the [Mn,Mg,Fe] solid solution series present in EH and EL groups, respectively). In addition, both the presence or absence of daubréelite and the content of Ni in kamacite were demonstrated to be consistent factors for the resolution of four distinct E chondrite groups: EHa, EHb, ELa, and ELb (see table below).

ENSTATITE CHONDRITE SUBGROUPS
Weyrauch et al., 2018
  EHa EHb ELa ELb
Troilite Cr <2 wt% Cr >2 wt% Cr <2 wt% Cr >2 wt%
(Mn,Mg,Fe)S Fe <20 wt% Fe >20 wt% Fe <20 wt% Fe >20 wt%
Daubréelite Abundant Missing Abundant Missing
Kamacite Ni <6.5 wt% Ni >6.5 wt% Ni <6.5 wt% Ni >6.5 wt%

A few other E chondrites with intermediate mineralogy have also been identified, including LAP 031220 (EH4), QUE 94204 (EH7), Y-793225 (E-an), LEW 87223 (E-an), and PCA 91020 (possibly related to LEW 87223). Studies have determined that these meteorites were not derived from the EH or EL source through any metamorphic processes, and some or all of them could represent separate E chondrite asteroids.


PART I: CHONDRITES, METACHONDRITES
PART II: PRIMITIVE ACHONDRITES, ACHONDRITES, STONY-IRONS, IRONS
PART III: MARTIAN METEORITES—GEOCHEMICAL CLASSIFICATION
PART IV: DIOGENITES—IUGS TAXONOMY


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


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