New data on the composition of plagioclase on the western flank of the Oktyabrsky deposit according to infrared spectroscopy

The plagioclases of the Kharaelakh intrusion on the western part of the Oktyabrsky deposit were analyzed by infrared spectroscopy. Analysis of 130 Fourier-IR absorption spectra of plagioclases with selective veriﬁcation of their chemical composition by X-ray spectral microanalysis indicates a regular change in the isomorphic series from albite (1150, 1096 cm–1) to anorthite (1142, 1275 cm–1), depending on the degree of diﬀerentiation of rocks in the intrusion. According to Fourier-IR spectroscopy, albite is conﬁned to olivine-containing and olivine gabbro-dolerites. Anorthite is evenly distributed in gabbro-dolerites, but predominates in leucocratic gabbro. Among the impurity elements in the structure of the mineral, Fe3+ is noted at peaks of 1580–1644 cm–1 in picrite gabbro-dolerites, where ore interspersed mineralization of chalcopyrite, pyrrhotite, and pentlandite is directly developed. In addition to iron impurities, aluminum, potassium, barium, and strontium are also characteristic impurities in plagioclases. The totality of the data used in the section of the intrusion increases the indicative value of plagioclases and can be recommended as an additional mineral criterion of ore content.