Liquid Immiscibility in Regions of Localized Shock-Induced Melting in the Elga Meteorite

详细

Abstract—The regions of localized shock melting (melt pockets) in one of silicate inclusions in IIE Elga iron meteorite were investigated with EMPA, SEM, TEM and Raman spectroscopy. It has been established that the mechanism of formation of melt pockets in Elga is of a mixed nature, being associated not only with melting in situ of the silicate matrix, but also with the intrusion of portions of the melted schreibersite–oxide rim into the silicate inclusion. Melt pockets have an emulsion texture, which is a sign of phase separation by liquid immiscibility in high-temperature shock melts. The emulsion texture formed by droplet-shaped exsolutions of siderite in the schreibersite matrix of one of the melt pockets has all the features of phase separation by liquid immiscibility at superliquidus temperatures. This convincingly indicates the extraterrestrial origin of siderite in the Elga meteorite.