@article{Tran Tuan_Tran Trong_Pham Ngoc_Gregory Shellnutt_Pham T._Izokh E._Pham Thi Phuong_Duangpaseuth_Soulintone_2022, title={Petrology of the Permian-Triassic granitoids in Northwest Vietnam and their relation to the amalgamation of the Indochina and Sino-Vietnam composite terranes}, volume={44}, url={https://vjs.ac.vn/index.php/jse/article/view/17002}, DOI={10.15625/2615-9783/17002}, abstractNote={<p>Granitoids from seven massifs in northwest Vietnam, including I-type granites (Nam Meng, Nam Rom, and Song Ma massifs) and S-type granites (Pu Si Lung, Kim Boi, Muong Lat, and Sam Son massifs) that distributed along the Dien Bien-Song Ma fault at the northern part of Truong Son Fold Belt, were studied to understand the mineralogy, whole-rock geochemistry, Nd-Sr isotopes, and U-Pb zircon geochronology. The I-type granitoid rocks vary from gabbro diorite to diorite and granodiorite to granite (SiO<sub>2</sub> = 52.4 - 71.1 wt.%) and from calc-alkaline to high K calc-alkaline to shoshonite (Nam Rom massif) series. Biotite in the I-type granitoid rocks has high Mg, intermediate to high Ti, and low Al (Phl-0.43 - Sid-0.29 - Ann-0.28); amphibole is edenite (Nam Rom massif) and ferro-edenite (Song Ma massif). The ASI varies from 0.64 to 1.14 (metaluminous); K/Na = 0.1-0.7; ratios of K/Rb, Rb/Sr and Rb/Ba varies from 179-334, 0.40-3.50, and 0.16-0.38; [La/Sm]<sub>N</sub>, [La/Yb]<sub>N</sub> and [Gd/Yb]<sub>N</sub> are varies within 1.08-4.92, 1.57-27.3, and 1.07-3.72, respectively. Their <sup>87</sup>Sr/<sup>86</sup>Sr and ƐNd(t) are highly enriched, respectively, from 0.7072 to 0.7319 and -12.2 to -6.67. The I-type granitoid rocks may be mixtures between mantle-derived and crustal components based on geochemical characteristics. In contrast, the Nam Meng magma was mantle-dominated, and the Nam Rom and Song Ma magmas were crustal-dominated. The S-type granitoid rocks include biotite granite and two-mica granite (SiO2 = 68.9-73.0 wt.%), varying from high K calc-alkaline to shoshonite series. The S-type granitoid rocks are distinct from the I-type granitoid rocks by sillimanite, cordierite, and muscovite. Biotite in the S-type granitoid rocks has high Ti and Al and low Mg. The mineral was partially replaced by muscovite. The ASI varies from 1.1 to 1.85 (peraluminous); K/Rb, Rb/Sr, and Rb/Ba vary within 161-188, 0.37-3.50, and 0.15-0.98; [La/Sm]N, [La/Yb]N and [Gd/Yb]N vary within 2.28-3.90, 5.93-16.8, and 1.72-2.93, respectively. The S-type granitoid rocks also have high <sup>87</sup>Sr/<sup>86</sup>Sr(i) (0.7227-0.7335) and low ƐNd(t) (-12.4 to -9.8) with TDM = 2.11-2.71 billion years, indicating a mature crust protolith. The in situ zircon U-Pb ages of the I-type granites are 289-296 Ma (Nam Meng massif) and 245-225 Ma (Nam Rom and Song Ma massifs), while those of the S-type granitoid rocks (Kim Boi and Muong Lat massifs) are 242-235 Ma. The above data suggest that the Indochina and Sino-Vietnam composite terranes produced the Permian-Triassic granitoid rocks in northwest Vietnam. The convergence had led to subduction activity forming Nam Meng granitoid, syn-collision activity forming Kim Boi, Muong Lat, and Sam Son massifs, and ended with post-collision activity forming Nam Rom and Song Ma massifs.</p>}, number={3}, journal={Vietnam Journal of Earth Sciences}, author={Tran Tuan, Anh and Tran Trong, Hoa and Pham Ngoc, Can and Gregory Shellnutt, J. and Pham T., Thuy and Izokh E., Andrey and Pham Thi Phuong, Lien and Duangpaseuth, Somsanith and Soulintone, Oneta}, year={2022}, month={Mar.}, pages={343–368} }