The new Angrite Meteorite from Northwest Africa, Oued Namous 001 is 4.56 billion years old!

Update: now classified in the Met Bull as Oued Namous 001, or ON 001 for short, a rare volcanic angrite.

Angrites are a rare basaltic rocks notable for their porosity, with large vesicles, and green kryptonite-inspired gemstones scattered throughout. Few have been found. They are among the oldest igneous rocks, with crystallization ages of 4.55 – 4.56 billion years (only EC002 is older, a recent find at 4.565 billion years).

By comparing the reflectance spectra of the angrites to that of several main belt asteroids, two potential parent bodies have been identified: 289 Nenetta and 3819 Robinson.

“Angrites are the most alkali-depleted basalts in the Solar System. While it has been suggested that the planet Mercury may be the source of the angrites, overwhelming evidence has been accumulated that they are fragments of a differentiated asteroid, probably >100 km in radius and with a metal core which, based on 182Hf-182W systematics, formed within ∼2 Ma of CAI formation (which represents the zero-point of the solar system). The origin and source lithologies of these fascinating rocks have been the topics of intense debates, and no consensus has yet been reached. However, the angrites are clearly igneous rocks and not impact melt-rocks or nebular condensates.” — Geochemistry 2012

The lack of volatile elements in angrites does argue for an origin in proximity to the Sun, possibly in the vulcanoid belt. The term “vulcanoids” refers to the hypothetical existence of planetoids that used to orbit the Sun closer than Mercury. They have left their original orbits by one or more planetary migration events.

“Angrite meteorites are some of the oldest materials in the solar system. They provide important information on the earliest evolution of the solar system and accretion timescales of protoplanets. The Chromium isotope ratio is homogeneously distributed among angrite meteorites within 13 parts per million, indicating that precursor materials must have experienced a global-scale melting such as a magma ocean. Cooling of the APB (Angrite Parent Body) took at least ∼8 Myr after its differentiation.” — Astrophysical Journal, 2019

Update from 2022 study of quenched angrites, offering a new hypothesis… “The quenched angrite meteorites reveal an oxygen isotopic disequilibrium between the matrix and olivine grains, which suggests the mixing of two bodies sourced from differing locations in the Solar System extremely early in Solar System history (< 4 Myr after the formation of calcium-aluminum-rich inclusions). We interpret our findings in terms of an- grite meteorites representing impact-melt rocks rather than shallow magmatic intrusions, recording evidence of impact-driven mixing. This mixing may have taken place in response to the inward migration of giant planets and hence would represent the earliest isotopic evidence for planetary migration in the early Solar System.” …wow! Just, wow.

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