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Darkhan K. Makatov
Darkhan K. Makatov
PhD Student
Abylkas Saginov Karaganda Technical University
PhD Student
Abylkas Saginov Karaganda Technical University
Karaganda
Kazakhstan

Articles

Geology
  • Date submitted
    2023-02-27
  • Date accepted
    2023-10-25
  • Online publication date
    2024-02-08
  • Date published
    2024-04-25

Microstructural features of chromitites and ultramafic rocks of the Almaz-Zhemchuzhina deposit (Kempirsai massif, Kazakhstan) according to electron backscatter diffraction (EBSD) studies

Article preview

Microstructural features of the main rock-forming minerals of host ultramafic rocks (olivine, orthopyroxene) and chrome spinel from ores of the Almaz-Zhemchuzhina deposit were studied using the electron backscatter diffraction method. For ultramafic rocks, statistical diagrams of the crystallographic orientation of olivine and orthopyroxene were obtained, indicating the formation of a mineral association in conditions of high-temperature subsolidus plastic flow in the upper mantle. The main mechanisms were translation gliding and syntectonic recrystallization. Olivine deformation occurred predominantly along the (010)[100] and (001)[100] systems. The textural and structural features of chromitites reflect plastic flow processes, most pronounced in lenticular-banded ores. Microstructure maps in inverse pole figure encoding show differences in the grain size composition of the ores: areas consisting of disseminated chromitites are characterized by a finer-grained structure compared to lens-shaped segregations of a massive structure. Analysis of microstructure maps shows that during the transition from disseminated to massive ores, there is a widespread development of recrystallization, adaptation of neighbouring grains to each other, resulting in homogenization of crystallographic orientation in aggregates. The data obtained develop ideas about the rheomorphic nature of chromitite segregations in ophiolite dunites. It is assumed that the coarsening of the structure of massive chromitites is critically associated with an increase in the concentration of ore grains during solid-phase segregation within a plastic flow, when individual chrome spinel grains, initially separated by silicate material, begin to come into direct contact with each other.

How to cite: Saveliev D.E., Sergeev S.N., Makatov D.K. Microstructural features of chromitites and ultramafic rocks of the Almaz-Zhemchuzhina deposit (Kempirsai massif, Kazakhstan) according to electron backscatter diffraction (EBSD) studies // Journal of Mining Institute. 2024. Vol. 266. p. 218-230. EDN FJNEDQ