The northern Kontum massif in central Vietnam, one of the most key tectonic and metallogenic terranes of the Indochina block, consists of numerous volcano-plutonic complexes including the Dai Loc granitic complex that formed an essential part of the early Paleozoic batholith of the massif. Rocks of the Dai Loc complex are granodiorite and granite in composition. Geochemically, the rocks are of sub-alkaline affinity and belong to high-potassium series. These rocks have moderate Aluminum Saturation Index (ASI) values of 0.76-1.19 and low Mg# values of 23-39. Zircon grains separated from the rocks have high ε Hf (t) values and old Hf model ages (T DM ) which varying from −0.7 to +4.8 and 0.9 to 1.1 Ga, respectively. All these characteristics, in conjunction with trace element features, suggest generation by partial melting of crustal source rocks with additional input of mantle-derived material. Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) zircon U-Pb analytical results from two samples revealed emplacement ages of the granite at 423 ± 2.2 and 427 ± 9.9 Ma. Our geochronological data provide evidence for early Paleozoic crustal evolution in Central Vietnam.

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The Indosinian Orogeny plays a significant role in tectonic background and magmatic evolution in Indochina and surrounding regions. Being a part product of the Indosinian magmatism in northwest Vietnam during late Permian-middle Triassic period, Muong Luan granitoid pluton dominantly consists of granodiorite, less diorite and granite. This pluton is located in the Song Ma suture and assigned to the Dien Bien complex. Geochemically, the Muong Luan granitoid rocks are characterized by a wide range of SiO 2 contents (59.9-75.1 wt%) and high K 2 O contents. They display typical features of I-type granites. The presence of hornblende and no muscovite and cordierite in the rocks further supports for I-type character of granitoids. The emplacement age of the Muong Luan pluton obtained by LA-ICP-MS U-Pb zircon is at 242-235 Ma, corresponding to Indosinian time. Zircon ε Hf values of-5.6 to-10.4, in combination with moderate Mg values of 34-45 suggested that the Muong Luan granitoid was derived from partial melting of mafic crustal source rocks, which are probably Paleoproterozoic in age as revealed by Hf model ages (T DM2 = 1624-1923 Ma).