Vol 57, No 8 (2019)

The paper suggests a thermodynamic approach to modeling the evaporation of lunar and meteorite matter. Comparison of the results of model calculations and experimental data demonstrates the high accuracy of the developed approach to description of thermodynamic properties of melts of lunar and meteorite substance and its behavior at evaporation. The observed relations of melt evaporation are consistent with the thermodynamic values characterizing the residual melts.

The metal of IIE irons provides evidence of fractionation in the interiors of an asteroid, but their fine-grained structures are incompatible with their endogenous origin. It was proposed that the metal underwent remelting on the surface of the parent body. Data on the mineragraphy and on the mineral and chemical composition of IIE irons (Elga, Verkhnodniprovsk, Tobychan, Miles, and Watson) indicate that the relatively fine-grained metal structure and anhedral schreibersite grains were probably formed by crystallization from melt. According to the calculated data on the bulk composition of the Elga metal and on the Fe–Ni–P phase diagrams, the crystallization of the first γ-Fe grains began at ~1511°С and ended at ~1060–1100°С with the formation of centimeter-sized polygonal crystals of taenite and anhedral schreibersite grains along their boundaries. The identical composition of the anhedral schreibersite, both along the borders of the taenite grains and on the rims around nonmetallic inclusions, indicates that they were formed simultaneously. Among the four generations of schreibersite, the anhedral schreibersite is distinguished for its high Fe/Ni ratio. It was also noted that the higher the crystallization temperature of schreibersite, the lower its Ni content. Similar metal structures were found in other types of meteorites: in IAB irons and in the metal of some mesosiderites, whose impact-related origin is thought to be the most probable. Hence, the mechanism of formation of IIE irons by means of shock remelting of fractionated metal and mixing with silicate fragments on the surface of the parent body may have also produced other meteorite types.

“The Meteorite Minerals Catalog” is the first edition in Russia prepared in the 21st century. It includes all the minerals found in meteorites, approved by the Committee on New Minerals and MMA Mineral Names approved before January 1, 2017, and mineral phases. The Russian and English names, chemical compositions, and meteorites or meteorite groups characterized by the considered minerals are given for all minerals and mineral phases. Notably, the first descriptions of all minerals and phases and references to publications are also given in the Catalog. Minerals whose origin is associated with specific processes are also presented. These include pre-solar meteorite minerals, refractory and ultra-refractory solar condensates, impact minerals of meteorites and products of the terrestrial weathering of meteorites.