Geochemical and geochronological studies of the Muong Hum alkaline granitic pluton from the Phan Si Pan Zone, northwest Vietnam: Implications for petrogenesis and tectonic setting

Abstract

The Phan Si Pan zone in northwest Vietnam is an important tectonic unit for understanding the geological evolution of the southeast Asian Block. Numerous late Permian A‐type granites outcrop in this zone. In this study, new geochemical and geochronological data derived from the Muong Hum alkaline granitic pluton in the Phan Si Pan zone were investigated for its petrogenesis and tectonic setting. Zircon U–Pb analyses of three samples yielded 206Pb/238U ages of (251.1 ±3.5) Ma, (251.2 ±3.8) Ma, and (253.9 ±1.5) Ma, respectively, coinciding with the ages of the acid member of magma from Emeishan large igneous province, southwest China. The Muong Hum granite has 10 000 × Ga/Al and A/CNK values of 4.70–4.93 and 0.87–0.90, respectively, as well as negative Eu anomalies. It shows significant depletion of Ba, Sr, Ti, and P, similar to features of A‐type granite. Zircons have positive εHf(t) values (+1.9 to +8.6) and Hf model ages (TDM1) of 595–846 Ma, originating a mantle source. Compared with the Panzhihua A‐type granite of the southwest China domain and other A‐type plutons of the Phan Si Pan zone, including Ye Yen Sun, Phu Sa Phin, Nam Xe, Tam Duong Phan Si Pan, and Taihe, the geochemical characteristics and zircon Hf isotopic compositions of the Muong Hum granite demonstrate an affinity of mantle magma. It is believed that the Phan Si Pan zone is an important part of Emeishan large igneous province. It was reworked by the Cenozoic Aillaoshan‐Red River shear fault to its present location.

Zircon U-Pb Geochronology, Geochemistry, and Sr-Nd-Hf Isotopic Composition of Ben Giang-Que Son Complex in the Southern Truong Son Belt: Implications for Permian–Triassic Tectonic Evolution

“…Using the internal structure features of zircons and their high Th/U ratios >> 0.1 (Table 4), we concluded that the magmatic rocks of the BG-QS complex were emplaced between 285 and 278 Ma years ago, corresponding to the early Permian period. These ages are similar to those reported by [51] (in Vietnamese with an English Abstract) but show a narrow range and are relatively older than previously published geochronological data (242-266 ± 4.4 Ma by hornblende Ar-Ar, Hung 1999; 251-271 Ma by biotite K-Ar, Khai 1979; and 300 ± 16 Ma by biotite K-Ar, Bao 1979).…”

“…Histograms of zircon ꜪHf(t) values (a); Hf model age (TDM2) from the BG-QS magmatic rocks (b); and initial ꜪHf values and Hf model ages of zircons (c,d) from this study, Vietnam (modified after[2]). Comparison data are from[2,[5][6][7]12,13,[47][48][49][50][51][52].…”

Petrogenesis and geological significance of charnockite in the Yinshan Block of North China Craton

“…The previous studies suggested that the Indochina block was formed by welding of continental and microcontinental plates such as South China, Sibumasu and Simao that separated from the Gondwana supercontinent (Lan et al 2000;Hoa et al 2008;Shu et al 2008;Kemp et al 2009;Cawood et al 2011;Liu et al 2012, Hieu et al 2013, 2017, Faure et al 2014 2015; Minh et al 2018), being related to the Emeishan Plume (Figures 8,9 and 13). Within the territory of Vietnam, the collision boundaries are mainly recognized in the Truong Son belt and the Kontum massif.…”

“…1000 km from the Gulf of Tonkin to the southeast corner of the Tibetan Plateau. It is generally considered as an Indochina southeastward extrusion of lithospheric-scale strike-slip up to 500 km because of the India-Asia collision (Faure et al 2014;Minh et al 2018). Along the Red River shear zone, there are high-grade metamorphic rocks.…”

“…A-type granites are located in Phan Si Pan zone and Tu Le basin. They are associated with the Emeishan Plume, been displaced along the Red River shear zone (Hieu et al 2013;Tran et al 2015;Usuki et al 2015;Minh et al 2018). Conversely, I-, and S-type granite are widely distributed along the Kontum massif, Truong Table 1.…”