The compositional variation of I-type granites: Constraints from geochemical analyses and phase equilibrium calculations for granites from the Qinling orogen, central China

•High-K calc-alkaline I-type granites have variable compositions.•Entrainment of both peritectic and residual minerals is inferred from lithochemical inspection.•Both partial melting and fractional crystallization are responsible for the compositional variation of the granites.•Granitic magmas can be generated by mixing of felsic melts with significant peritectic and residual minerals.