HUT 18034

Classification: Enstatite Achondrite (Aubrite)

Explainer: This means that the sample is from an asteroid parent body. It is a rare type of achondrite meteorite rich in enstatite (magnesium-rich) pyroxene called an aubrite. Aubrites are highly reduced and predominantly composed of enstatite, with albitic plagioclase, diopside and forsterite also present. Most are breccias, with clasts of igneous origin formed by melting and fractional crystallisation. This is a brecciated (broken up) sample. Impact processes are responsible for the observed brecciation in meteorites. They don’t have a unique petrologic type (metamorphic grade) as every clast is slightly different in petrology. Aubrites are named after Aubres, in France where the first enstatite achondrite fall has been observed. You can see more about where this sample fits into the meteorite classification scheme by looking at this page.

Description: Taken from the Meteoritical Bulletin for HUT 18034

History: The meteorite was recovered as part of the Lost Meteorites of Antarctica project, which was funded in the UK by the Leverhulme Trust and supported by the British Antarctic Survey and the University of Manchester. These samples were collected as part of the project’s first field season in austral summer December 2018 – January 2019 by a two person field party consisting of Katherine Joy and Julie Baum. Found on firn. Altitude 1152 m.

Physical characteristics: Mass: 0.81 g. Pieces: 1. Dimensions: 2 × 2 × 1 cm. An irregular, white-grayish part-stone with visible white grains (enstatite) and 40% black fusion crust. Several orange-brownish stained areas sometimes with silvery metallic grains are visible.

Petrography: The section consists of predominantly enstatite grains up to 3 cm in size in a brecciated matrix dominated by enstatite. Additional minerals include diopside (~8%), some containing abundant enstatite exsolution lamellae, ~4% feldspar, ~3% forsterite and occasional grains of Ti-bearing troilite, daubreelite and schreibersite.

Mineral compositions and geochemistry: All analyses by EPMA. Olivine: forsterite Fo100±0 (N=7). Pyroxene: En98.9±0.4Fs0.0±0.0Wo 1.1±0.4 (N=10) and En55.9±1.2Fs 0.1±0.1Wo 44.0±1.2 (N=6). Plagioclase An5.0±4.6Ab92.0±3.8Or 3.0±0.9 (N=5). Oxygen Isotopes (J. Malley, R. Greenwood and R. Findlay, OU): One fragment was analyzed for oxygen isotopes by laser fluorination at OU. An ~18 mg homogenized sample yielded the following results (per mil deviation from VSMOW): δ17O=2.414, δ18O=4.531, Δ17O=0.058. Δ17O values are calculated using a slope of 0.52. The oxygen isotope analysis of the fragment plots close to the terrestrial fractionation line and is only slightly displaced from the aubrite analyses of Newton et al. (2000) and Barrat et al. (2016).

Specimens: 0.672 g type specimen (main mass) held at NHM.

Project comments: No comments

Sample images and videos:

HUT 18034 sample in the field on ice. Image: Lost Meteorites of Antarctica / The University of Manchester
HUT 18034 sample in the lab after defrosting. Image: Lost Meteorites of Antarctica / The University of Manchester
HUT 18034 sample in the lab after defrosting. Image: Lost Meteorites of Antarctica / The University of Manchester