The article is devoted to determining the P-T conditions and formation mechanisms of the Gubanov intrusion (Wiborg rapakivi granite massif) using a suite of petrographic and geochemical methods combined with thermodynamic modelling (rhyolite-MELTS, machine learning). Microstructural analysis of plagioclase resorption made it possible for the first time to estimate the vertical dimension of the intermediate magma chamber at 1.5-2 km and the crystal accumulation/settling timescale (< 0.2 Ma) as the duration of the early stage of rock crystallization. Combined thermobarometry (mineral equilibria, ML algorithms, rhyolite-MELTS) constrained the crystallization interval to T = 840-660 °C, P = 5.5-4.0 kbar at fO₂ ≈ FMQ and H₂O in the melt ≈ 6-10 wt.%. It is shown that the rocks of the contact zone between phases formed by partial melting of phase 2 material (producing a melt with 80-84 wt.% SiO₂) triggered by phase 3 melt and subsequent mixing of these components. The results refine the evolutionary model of the Wiborg massif and demonstrate the effectiveness of integrating traditional and modelling petrology methods.