The first Al-Cu-alloy-bearing unmelted micrometeorite suggests contributions from the disrupted ureilite protoplanet

• Discovery of the first unmelted micrometeorite containing cu-al alloy. • The micrometeorite indicates collisional mixing of cu-al alloy with CV3 silicates. • Cu-Al-alloy bearing micrometeorites are derived from the same parent body as the CV3 khatyrka. • The ureilite parent body was the source of the Cu-Al-bearing projectile. • Cu-Al alloy forms during reduction on disrupted protoplanets. We report the discovery of Al-Cu-alloys within a coarse-grained micrometeorite from the Congo. Oxygen isotope ratios of the sample are consistent with a CV3 source, similar to the Khatyrka meteorite. The petrology of the micrometeorite is also similar to Khatyrka and testifies to the disequilibrium impact mixing between the CV3 parent body and a differentiated body, which was the source of the Al-Cu-alloys. The oxygen isotope composition, however, suggests either limited mixing with projectile silicates or a differentiated projectile with oxygen isotopes close to the CCAM. The most plausible origin of the Al-Cu-alloys is the desilication of an aluminous igneous protolith by hydrothermal activity under highly reduced conditions. We argue that the ureilite parent body is the most likely source for the projectile owing to its silicic magmatism, late-stage reduction and similar oxygen isotope ratios. Al-Cu-alloys can, thus, be found on the disrupted remnants of such protoplanets.