Thin section of the Erg Chech 002 meteorite (ungrouped achondrite)
Erg Chech 002 (EC 002) is a meteorite discovered in May 2020 in the Erg Chech region of the Sahara Desert, Algeria. It is classified as an ungrouped achondrite, meaning it does not fit into existing meteorite classification groups. Its age is approximately 4.565 billion years, making it one of the oldest known volcanic rocks in the solar system.
Description in Meteorite Bulletin 109: “Unbrecciated igneous texture. Sporadic pyroxene megacrysts (ranging in size from 1.7 to 11.5 mm in the studied thin section), exhibiting angular or ellipsoidal and embayed shapes, and comprising orthopyroxene (of varying composition), pigeonite and augite occur within a dominant, medium to relatively coarse grained groundmass. The cores of each of the analyzed megacrysts are fairly homogeneous in composition, but all are mantled by zones of different composition and distinct, fine grained rim overgrowths against the groundmass parallel to grain outlines (irrespective of geometry). Some low-Ca pyroxene cores contain thin lamellae and some larger inclusions (up to 300 µm) of Ti-poor chromite. The groundmass representing the major portion of the specimens (mean grainsize ~1.5 mm) is composed predominantly of exsolved pigeonite (commonly as radiating clusters of prismatic grains) and lath-like sodic plagioclase (zoned from irregular oligoclase cores to albitic rims with oriented dagger-like K-feldspar exsolution blades) together with accessory Ti-chromite, ilmenite (some as rims on chromite), troilite, silica polymorph (with a curved “fish-scale” fracture pattern suggestive of cristobalite), merrillite, and rare Ni-poor metal (in composite grain clusters with ilmenite, Ti-chromite and troilite). Secondary weathering products include minor goethite after primary troilite and metal, and sporadic very thin veinlets of calcite.”
This thin section is owned by Szymon Kozłowski and was scanned on September 17, 2024, using a Keyence VHX-7000 polarizing microscope in both plane- and cross-polarized modes at the Department of Geochemistry, Mineralogy and Petrology, University of Warsaw, Poland.
Full thin section
Zoom #1
Zoom #2
