Report on classification of Antarctic meteorites from the 2014/15 KOREAMET season

Abstract

Korean Expedition for Antarctic Meteoteorite (KOREAMET) has recovered 81 meteorites from the blue-ice fields of the Reckling Peak (RKP), Mount DeWitt (DEW), and Elephant Moraine (EET) in the Victoria Land, Antarctica, 2014/15 season. Here we report on classification of the meteorites and describe details of some remarkable meteorite samples. Optical microscope and scanning electron microscope (JEOL JSM-6610) at KOPRI were used for petrography. Field-emission electron microprobe (JEOL JXA-8530F) at KOPRI was used for a quantitative analysis operated at 15kV and 10nA and a long-time x-ray mapping at 15kV and 50nA. Eighty one meteorites of the 2014/15 KOREAMET season include 72 ordinary chondrites (33 H-group, 37 of L-group, 2 of LL-group), 4 carbonaceous chondrites (3 of CM-group, 1 of CK-group), 3 eucrites, 1 ureilite, and 1 acapulcoite. Most of ordinary chondrites are equilibrated (petrologic type 5 or 6) except a LL chondrite (EET 14017). (Note that all meteorite names here are preliminary yet.) EET 14017 is the most primitive meteorite (type 3.05) in our collections. Almost all known types of chondrules are observed in the EET 14017, including PO (porphyritic olivine), PP (porphyritic pyroxene), POP (porphyritic olivine and pyroxene), BO (barred olivine), RP (radial pyroxene), CC (cryptocrystalline), and Al-rich chondrules. Glassy mesostasis with tiny nucleates (<100 nm) is well preserved. Ca,Al-rich inclusions (CAIs) are very rare (<1 vol%). Two CM chondrites are heavily altered (type 2). Only small amounts of chondrules and CAIs are retained. A CK chondrite (EET 14007) shows poorly-defined chondrules (type 5). Olivine and low-Ca pyroxene of the meteorite are equilibrated (Fa39.8±0.3, 2SD

Fs25.5±1.3) and plagioclase is Na-rich (Ab29~56). It contains abundant Cr-rich magnetite (Cr2O3 3.9~4.9 wt%). Two out of 3 eucrites are polymict eucrites consisted of various clasts. One eucrite (EET 14057) consists of coarse-grained pigeonite (En52.4±1.3Fs45.9±1.3) with augite lamellae (En39.4±1.0Fs17.2±0.9) and calcic plagioclase (Ab5.8±1.1An94.0±1.1), and is unbrecciated. Pyroxene and plagioclase grains of the EET 14047 show planar deformation features. EET 14053 is a ureilite composed of coarse-grained olivine (Fa14.9±0.6

CaO 0.24 ~ 0.32 wt%

Cr2O3 0.58 ~ 0.75 wt%) and pyroxene (En82.8±0.3Fs12.8±0.4) grains, and characterized by their reduced rims in contact with carbon-rich matrix (e.g., graphite). EET 14076 is classified as an acapulcoite, composed of fine-grained olivine (Fa10.4±1.0), orthopyroxene (En87.2±1.1Fs10.5±0.6), Cr-bearing diopside (Wo43.5±3.5En52.0±3.0

Cr2O3 1.0~1.4 wt%), sodic plagioclase (Ab75.3±1.8An22.0±1.5), apatite, merrillite, and chromite.