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Vol. 29 (2026 year), No. 2, DOI: 10.21443/1560-9278-2026-29-2

Rakhimov I. R., Vasiliev A. M., Samigullin A. A.
Reflection of petrologic regularities in the mineralogy of tonalite-granites and diorite inclusions in them: Comparison of granitoid massifs of the Urals and the Alps

Orogenic granitoid massifs contain a variety of mafic inclusions (autoliths, xenoliths, mingling dikes). These include predominantly diorite-series inclusions, which visually contrast with the host tonalite-granite associations but have similar mineral and chemical compositions. The origin of these inclusions is controversial, and even the use of a range of modern precision methods does not always resolve the issue. The paper provides a petrographic, mineralogical, and geochemical review of orogenic granitoids from three massifs in two fold belts of the world: Adamello (Southern Alps), Akhun (Southern Urals), and Shabry (Middle Urals). The massifs are composed of tonalites and granites containing uniform angular and rounded diorite inclusions. The results obtained have shown that all rock varieties are composed of the same set of minerals of fairly similar composition (Ca-Na plagioclase, quartz, potassium feldspar, biotite, and amphibole), differing only in their ratios. Variations in mineral composition, particularly biotite, amphibole, and plagioclase indicate the significant influence of a fluid phase released during crystallization of a water-saturated melt. The use of amphibole-plagioclase thermobarometers has shown that the trapped diorites and host tonalite-granites crystallized under similar conditions (usually in the range of 700–800 °C and a pressure of 2–4 kbar). Diorite inclusions are autoliths, i. e., fragments of either crystallized rocks (angular inclusions) or trapped portions of partially crystallized melt (rounded inclusions) from the lower part of a single intrusive chamber. Patterns of their distribution and chemical composition in matrix tonalite-granites and diorite inclusions indicate their genetic unity. Patterns of change in the chemical composition of rocks of all massifs indicate a uniform course of their evolution. Binary diagrams show that similar geochemical patterns of rocks from all massifs indicate the uniformity of their evolutionary course.

(in Russian, стр.37, fig. 11, tables. 2, ref 37, AdobePDF, AdobePDF 0 Kb)