¹Giovanna Agrosì, ²Paola Manzari, ¹Daniela Mele, ^3,4Johan Villeneuve, ⁵Tiziano Catelani, ⁶Mattew J. Genge, ⁷Luca Bindi
Meteoritics & Planetary Science (in Press) Open Source Link to Article [DOI: 10.1111/maps.70215]

¹Dipartimento di Scienze della Terra e Geoambientali, Università di Bari, Bari, Italy ²Agenzia Spaziale Italiana, Centro Spaziale Giuseppe Colombo, Matera, Italy
³Centre de Recherches Pétrographiques et Géochimiques, CNRS, Nancy, France
⁴Universite Paris-Cite, Institut de Physique du Globe de Paris, CNRS, Paris, France ⁵Centro di Servizi di Microscopia Elettronica e Microanalisi, Università di Firenze, Florence, Italy
⁶Department of Earth Science and Engineering, Imperial College London, London, UK ⁷Dipartimento di Scienze della Terra, Università di Firenze, Florence, Italy
Published by arrangement with John Wiley & Sons

We report the discovery of the second (Al,Cu)-alloy–bearing micrometeorite, FB-A2, 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 μm (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.

¹Jin-Young Lee, ²Jeongmin Kim, ¹Sei-Sun Hong
Meteoritics & Planetary Science (in Press) Open Source Link to Article [DOI: 10.1111/maps.70216]

¹Quaternary Geological Research Center, Korea Institute of Geoscience and Mineral Resources, Daejeon, Korea
²Research Center of Earth and Environmental Sciences, Korea Basic Science Institute, Cheongju, Korea
Published by arrangement with John Wiley & Sons

We present the first micrometer-scale, phase-resolved compositional characterization of impact melt glass from the Hapcheon crater (~1.4 km apparent diameter), the first confirmed impact structure on the Korean Peninsula, integrating EPMA-WDS (5 μm spot), confocal Raman spectroscopy (<1 μm spot), XRD, and 40Ar/39Ar step-heating geochronology. EPMA of 37 points resolves three compositionally distinct groups separated by a clear compositional gap: silica-glass cores (CORE; n = 23; 98.4 wt% SiO2, K2O 0.023 wt%), feldspathic–mafic mantling glass (MANTLE; n = 6; ~55 wt% SiO2, K2O 2.24 wt%), and feldspathic glass clasts (UNCERTAIN; n = 8; ~61 wt% SiO2, K2O 3.10 wt%), demonstrating phase-segregated melting of the quartz and feldspathic–mafic fractions of the Cretaceous Dongmyeong target rock rather than whole-rock homogenization. Confocal Raman spectroscopy confirms coesite in 74% of 34 spectra and identifies diaplectic quartz glass, documenting micrometer-scale shock heterogeneity; a 30-point colocation data set confirms coesite within the ultralow-K2O glass phase. The ultralow K2O causes systematic 40Ar/39Ar age overestimation through inherited 40Ar; all seven plateau ages (1.8–5.6 Ma) exceed the independent 10Be burial age of 1.33 Ma. Step-heating Ca/K systematics confirm multiphase assemblages, and inverse-isochron 40Ar/36Ar intercepts independently corroborate inherited 40Ar. The youngest compositionally anchored age brackets the impact at 1.33–3.07 Ma (Plio-Pleistocene).