Magmatic redox conditions govern the behavior of multivalent elements and strongly influence magma evolution, differentiation, and ore-forming potential. Constraining oxygen fugacity (fO₂) is therefore essential for understanding subduction-related magmatic systems, which play a central role in Earth processes and carry major socio-economic relevance, from volcanic hazards to metal-rich deposits. This thesis presents high-pressure (200 MPa), high-temperature (1030-870°C) fractional crystallization experiments conducted under water-saturated conditions across a wide redox range (FMQ-1 to FMQ+7). The experiments examine vanadium (V) and scandium (Sc) partitioning between silicate minerals, Fe-Ti oxides, and melt. The results establish refined and novel V- and V-Sc-based oxybarometers for olivine-, pyroxene-, and Fe-Ti oxide–melt systems. These calibrations reproduce experimental fO₂ with high precision (±0.3-1 log unit), enabling robust reconstruction of redox conditions from basaltic to felsic magmas and providing an experimentally validated framework for tracing redox evolution from mantle to crust.