ИСТИНА

Meteorite Elga relates to differentiated IIE irons formed by impact-induced metal-silicate melting and mixing [1, 2, and ref. therein]. Elga is composed of a Fe0.92Ni0.08 matrix with rounded silicate inclusions of 1 – 15 mm in size which contain pyroxene and apatite grains embedded into SiO2-rich glass of rhyolite-like composition and usually connected by silicate veins or cracks [3, 4]. Some portions of Elga exhibit shock effects evidence of two impacts separated in time [5]. The former one resulted in the appearance of articulated siderite-bearing Sch-Ox rims developed around silicate inclusions and along the cracks in metal matrix. The latter shock event manifests itself by fragmentation and brecciation of these rims, and by injection of melted phosphide and oxide matter from the silicate/FeNi boundary into the silicate inclusions. The observations are consistent with the model of the melt pockets generation during a passage of the shock wave through a pore space in solid matter [6, 7]. Siderite has been found in all shock-produced zones [5]. The early (primary) siderite occurs in schreibersite-oxide rim. Therefore a mechanism of stratified Sch-Ox rim formation is a key to understanding the mechanism and origin of siderite in Elga.