<p>The current work is dedicated to studying the occurrence of fine- to coarse-grained magnetite crystals in migmatites of Chandrapur area located in Guwahati, along the northern fringe of the Assam-Meghalaya Gneissic Complex, Northeast India. The objective of this contribution is to present a novel approach demonstrating the origin of magnetite in the migmatites of our study area. Field investigations reveal that the gneissic rocks within the study area are penetrated by numerous pegmatitic veins of varying sizes. The late Pan-African tectonothermal event is deemed responsible for the pegmatitic intrusions in the study area. The pressure-temperature (P-T) conditions estimated from the migmatites revealed that fluid-present partial melting of the thermally elevated gneissic rocks during the tectonothermal episode was driven by the intrusion of volatile-laden pegmatitic melts. Subsequently, the partially molten rocks mingled with the K-rich pegmatitic magma, resulting in a mixed rock now preserved as neosome. Petrographic examinations reveal that the neosome displayed different degrees of hybridization, as indicated by the extent of amphibole-biotite transformation. Higher degrees of hybridization led to more extensive replacement of amphibole by biotite. The neosomes are also characterized by fine- to coarse-grained magnetite crystals. Based on the findings of this work, we infer that the transfer of K₂O from the pegmatite magma to the partially molten rocks or neosome assisted in the breakdown of amphibole to biotite. The replacement reaction of amphibole to biotite led to the liberation of FeO, which was subsequently converted into magnetite (Fe₃O₄) in the prevailing oxidizing conditions. The presence of magnetite in the neosome reflects the dominance of an oxidizing environment during magma interaction and evolution.</p>