Petrology of the Permian-Triassic granitoids in Northwest Vietnam and their relation to the amalgamation of the Indochina and Sino-Vietnam composite terranes

Abstract

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 (SiO2 = 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]N, [La/Yb]N and [Gd/Yb]N are varies within 1.08-4.92, 1.57-27.3, and 1.07-3.72, respectively. Their 87Sr/86Sr 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 87Sr/86Sr(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.

3D models for hydrothermal copper ore bodies at Sin Quyen deposit, North Vietnam: A case report for ore reserves and prediction of hidden mineral resource potential

“…1 ). The rocks within this zone have been dated with various periods such as 2360 - 1960 Ma, 1700 - 1659 Ma, 800-750 Ma, 575-430 Ma, 263 - 240 Ma , 82-22 Ma, 40 - 22 Ma, 34-5 Ma, and 17-5 Ma [ 1 , 2 , 36 , [41] , [42] , [43] , [44] , [45] , [46] , [47] , [48] , [49] , [50] , [51] , [52] , [53] , [54] ]. The Sin Quyen deposit was found in the 1970s by Vietnamese, Russian, Polish, and Chinese geologists [ 55 ].…”

Gravity Data Enhancement Using the Exponential Transform of the Tilt Angle of the Horizontal Gradient

“…Two main factors, the (i) collision of the Indo-Australian and Eurasian plates and (ii) subduction of the Pacific plate under Eurasian plate, explain that the Tuan Giao area has high dynamic activities. The Tuan Giao is a mountainous area with a complicated geological structure (Figure 9), dominated by many active faults, such as the Dien Bien Phu fault, Son La fault, Song Da fault and Song Ma fault [55][56][57]. From the works of many researchers, young materials (i.e., magmatic rocks) intruded into old sedimentary rocks environment through the faults (Figure 9) [55,56].…”