Petrology and mineralogy of Beardsley H5 chondrite; Implications for impact melting

Niihara, Takafumi*; Tsuzuki, Yuki*; Misawa, Keiji*; Yokoyama, Tatsunori; Yoneda, Shigekazu*

no journal, , 

Some brecciated chondrites contain alkaline-rich igneous clasts. Their formational process is explained as early nebular condensates followed by shock melting. The Beardsley chondrite (H5) possesses large amounts of Rb compared to other H chondrites. However, detailed petrological and mineralogical signatures of Beardsley are still lacking and there is no petrological and mineralogical evidence for alteration such as presence of halite/sylvite or other alkaline-rich phases contained in other H chondrites. Here we conduct petrological and mineralogical study for the meteorite, especially to clarify secondary effect(s) and distribution of alkaline elements on the chondrites and discuss the petrogenesis of Beardsley. Petrological and mineralogical features of Beardsley are similar to those observed in impact melted H-chondrites, implying that the grey lithology is a product of impact melting event(s). On the other hand, the higher KO content in the grey lithology cannot be explained only by an impact melting process but is still unclear at this stage.