40Ar/39Ar Analyses of Orvinio (H6): Further Lessons on Incomplete Degassing of Impact Melt Breccias

Orvinio is a classic impact melt breccia which was previously listed as an L-chondrite but is actually an H-chondrite whose thermal history needs to be reinterpreted in this context. The authors obtained a new specimen of Orvinio and analyzed individual relic clasts and impact melt matrix samples in an attempt to provide improved Ar-40/Ar-39 age data, and perhaps eliminate the ambiguity in the thermal history of the meteorite. This study hopes to reach a better understanding of the use and interpretation of chondritic impact melt argon profiles, and of the history of the H-chondrite parent body or bodies.