The Borodino meteorite: evolution on parent body

The article discusses the results of a mineralogical and petrographic study of the Borodino meteorite (H5). For the first time, meteorite minerals are described and their chemical compositions are given. The following were found in the Borodino meteorite: olivine (Fa 18.16±1.15), low-Ca pyroxene – (clino)enstatite (En 81.37±1.73, Wo 1.18±0.31), high-Ca pyroxene – augite (En 57.23±1.57, Wo 39.38±2.68), diopside (En 51, Wo 45), pigeonite (En 69, Wo 6), plagioclases – oligoclase (An 12.16±1.24, Or 5.68±2.12), andesine (An 48.23±1.84, Or 1.23±0.12), anorthoclase (An 0, Or 36) and sanidine (An 0, Or 40.00±1.1), and weakly crystallized glasses of feldspathic composition, merillite and chrome spinel. The data obtained made it possible to estimate the degree of terrestrial weathering of the meteorite as W0 and the stage of impact metamorphism (S1-2), which suggests good preservation of the meteorite material. The composition of olivine and chrome spinel, determined using the EPMA method, was used to estimate the peak temperature of thermal metamorphism at 720°C, which falls within the temperature range (670–740°C) characteristic of petrological type 5 chondrites. The presence of high-Ca pyroxenes, large grains of Ca–Na–Mg phosphates and chromite-pigeonite aggregates in the meteorite matrix indicate prolonged heating of the material.