Lo Gam structure (including Phu Ngu) in northeast Vietnam comprises Permian – Triassic gabbro-peridotite, monzogabbro, high-Al granite and syenite intrusive blocks. The studies have also revealed that gabbro – syenite magmas in folded structures around southeastern margin of the Song Chay anticlinoria form three association types distinguished by their co-existing mineral assemblages, mineralogical compositions and geochemical indexes (titanium content and alkalinity): layered peridotite- gabbro (Nui Chua complex), biotite granite (Phia Bioc complex) and compositionally heterogeneous gabbro-syenite. The uniformity of their geochemical and isotopic compositions indicates, on the one hand, generic relationship of the gabbro and syenite, and geochemically common source origin of the magmas, on the other. Being enriched in large ionic lithophile elements (LILE), rare earth elements (REE) and strongly depleted in Nb, Ta and Zr the gabbroid and syenite magmas refl ect typical geochemistry of an above-subduction-zone affi liation. This is the basic feature of Permian – Triassic pluton – volcanic and plutonic magmatic associations in various geological structures in northeastern Vietnam. The formation ages of lherzolite and monzogabbro (Nui Chua complex), gabbro, syenite and biotite granite (Cho Don area) are 251–246. Ma (U-Pb, zircon, SHRIMP, Ar-Ar).