Abstract
We investigated the microstructural and crystallographic features of quartz from complex vein systems associated with the development of thrust and shear deformations in Western Transbaikalia using electron back scatter diffraction (EBSD) and optical microscopy. Vein quartz systems were studied to obtain insights on the mechanisms and localization of strains in quartz, in plastic and semibrittle conditions close to the brittle–ductile transition, and their relationship to the processes of regional deformations. Five types of microstructures of vein quartz were distinguished. We established that the preferred mechanisms of deformation of the studied quartz were dislocation glide and creep at average deformation rates and temperatures of 300–400 °C with subsequent heating and dynamic and static recrystallization. The formation of special boundaries of the Dauphiné twinning type and multiple boundaries with angles of misorientation of 30° and 90° were noted. The distribution of the selected types in the differently oriented veins was analyzed. The presence of three generations of vein quartz was established. Microstructural and crystallographic features of vein quartz aggregates allow us to mark the territory’s multi-stage development (with the formation of syntectonic and post-deformation quartz).
Highlights
The structural and textural feature fabrics of vein quartz are formed as a result of dynamometamorphism, and they are characterized by significant diversity
We studied the microstructural and crystallographic features of vein quartz using an optical microscope (Leica DM750P, Leica Microsystems, Wetzlar, Germany) by reflected light and transmitted light using a scanning electron microscope (SEM)
Each type corresponded to separate morphological parameters and the degree of deformation manifested corresponded to the different conditions for the formation of mineral aggregates and preferred modes of deformation
Summary
The structural and textural feature fabrics of vein quartz are formed as a result of dynamometamorphism (a cataclastic, dislocation metamorphism), and they are characterized by significant diversity. They reflect the conditions for the development of the geological history of the lithosphere block to which it belongs [1,2,3]. The formation of the microstructure of mineral aggregates is influenced by the rate of strain, temperature, and the presence of fluid [4,5,6,7] In this regard, the analysis of defective quartz structures (boundaries, sub-boundaries and twins), along with the analysis of gas–liquid inclusions, indicator impurities, and other geochemical data, provides important information regarding the mechanisms, stages, and conditions of the dynamometamorphic processes.
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