Abstract <p>The western Shillong Plateau records Early Cretaceous mafic magmatism emplaced as dykes, sills, and apophyses into the Precambrian gneisses, Pan-African granitoids, and Gondwana sandstones. These intrusives (basalts, micro-dolerites, and dolerites) are temporally linked with the Sylhet Trap volcanism associated with Kerguelen plume activity during Gondwana breakup (~130 Ma). An Sm-Nd whole-rock isochron from five samples yields a crystallization age of 117 ± 24 Ma, consistent with published ⁴⁰Ar/³⁹Ar ages of Sylhet Trap flows (116 ± 3.5 Ma). Geochemically, the studied intrusives are subalkaline-tholeiitic and metaluminous, similar with the Sylhet Trap flows and associated mafic dykes. Major- and trace-element variations record fractional crystallization of olivine, clinopyroxene, and plagioclase. Pronounced enrichment in the light rare earth elements (LREE; La-Sm) and the systematic depletion of HREE in the chondrite-normalized REE patterns of the studied mafic intrusives producing fractionated profiles suggest source enrichment or lower degree of partial melting. In addition, the negative anomalies in Ho, Er, and Yb observed in the intrusives, also point to melting of the mantle under high-pressure conditions within the garnet stability field. Negative Nb-Ta anomalies combined with elevated LILE and LREE contents and evolved εNd(t) value (≈ -3) of the studied intrusives highlight significant crustal assimilation. Although such features are commonly attributed to arc-like tectonic settings, they are also considered as a diagnostic "overprint" in Continental Flood Basalts (CFB) which has interacted with ancient continental crust. The plots of the studied samples in the "Within-Plate" fields in the tectono-magmatic discrimination diagrams [e.g. Zr vs. Ti and Zr-Y-Ti] are consistent with derivation from an intraplate magmatic regime, typically linked to mantle plume. Additionally, the samples exhibit a vertical/oblique displacement toward higher Th/Yb in the Th/Yb vs. Nb/Yb diagram and also the plot of the samples along with the upper- and lower-crustal contamination trends in the (Th/Ta)_PM vs. (La/Nb)_PM space point towards crustal contamination. The overall OIB-like incompatible element patterns of the studied intrusives and the regional age constraints along with the plateau moving northwards thus indicate that the "arc-like" signature is a crustal inheritance rather than a primary tectonic environment. These results demonstrate that the studied intrusives represent feeder-like components of the Sylhet Trap magmatism, derived from the Kerguelen plume but variably modified by continental lithosphere during emplacement.</p> Research highlights <p><UnorderedList Mark="Bullet"> <ItemContent> <p>Mafic intrusives (basalts, micro-dolerites, dolerites) were emplaced into Precambrian basement and Gondwana sandstones during the Early Cretaceous (117 ± 24 Ma), contemporaneous with the Kerguelen derived large igneous province (Sylhet Traps).</p> </ItemContent> <ItemContent> <p>Petrography shows plagioclase–clinopyroxene dominance with hyalophitic to ophitic textures, reflecting variable cooling histories.</p> </ItemContent> <ItemContent> <p>Geochemistry indicates subalkaline, metaluminous, tholeiitic affinity with olivine-clinopyroxene-plagioclase fractionation trends.</p> </ItemContent> <ItemContent> <p>The LILE–LREE enrichment, Nb–Ta anomalies, and evolved εNd_(t) value (≈ −3) suggest plume-derived melts modified by crustal assimilation.</p> </ItemContent> </UnorderedList></p>