The first discovery of a shocked, metasomatised CV3 chondrule-fragment in a (Al,Cu)-bearing micrometeorite

We report the discovery of the second (Al,Cu)-alloy–bearing micrometeorite, FBA2, recovered from Mount Gariglione (southern Italy), representing the sixth such occurrence worldwide. Although chondritic in nature, FB-A2 differs markedly from previously described microspherules. It is a scoriaceous micrometeorite dominated by silicates and contains a relict clast composed of Mg-rich olivine and pyroxene phenocrysts set in a Fe-rich silicate matrix. The particle rim hosts fine aggregates of phosphates, magnetite, Ni-bearing magnetite, and sulfides, whereas the interior contains nepheline crystals. A 120 lm (Al,Cu)-alloy grain occurs at one corner of the particle. The porphyritic texture of the clast indicates a chondrule fragment—the first identified in an (Al,Cu)-bearing micrometeorite—while polyhedral sub-grain boundaries and metal–sulfide veins record shock metamorphism. Iron-rich alteration of relict silicates is consistent with high-temperature (<560 °C) metasomatism typical of CV3 chondrites and is supported by oxygen isotope compositions close to the Carbonaceous Chondrite Anhydrous Mineral Line. Brecciation of chondrule olivine suggests impact-induced fluid pressure excursions during early Solar System metasomatism, whereas impact melt enveloping elongate olivines indicates a later impact that introduced the (Al,Cu)-alloys. Overall, the texture, mineralogy, and isotopic composition of FB-A2 provide the most detailed constraints yet on the origin of (Al,Cu)-bearing micrometeorites and confirm a genetic link to the Khatyrka meteorite.