Petrogenesis of an Early Cretaceous Xiabie Co I‐type Granite in Southern Qiangtang, Tibet: Evidence from Geochemistry, Geochronology, Rb‐Sr, Sm‐Nd, Lu‐Hf and Pb isotopes

Abstract

Cretaceous magmatism is widely distributed on both sides of the Bangong–Nujiang suture zone (BNSZ). These rocks record the subduction to closure history of the Bangong–Nujiang Tethys Ocean (BNO) and the collisional history between the Lhasa (LS) and Qiangtang (QT) terranes. The Xiabie Co granite in Nyima County, which located on the southern margin of the QT terrane, Tibet. In this study, whole‐rock geochemistry; Rb‐Sr, Sm‐Nd, and Pb isotopes; and laser ablation inductively coupled mass spectrometry (LA‐ICP‐MS) zircon U‐Pb ages and Lu‐Hf isotopes of the Xiabie Co granite in the Nyima area have been studied to constrain its petrogenesis and tectonic setting. Our study can help explain the tectonic evolution of the BNSZ and crust‐mantle interaction. Zircon U‐Pb dating indicates that the granite was emplaced at ca. 120 Ma. The granite contains a small amount of hornblende and has high silicon (SiO2 = 73.97–78.03 wt%), potassium (K2O = 4.75–6.53 wt%), and total alkali (K2O + Na2O = 7.98–8.98 wt%) contents; low calcium content (CaO = 2.33–4.11 wt%); and variable A/CNK (1.00–1.18) and A/NK (1.09–1.22) values. The P2O5 content of the granite negatively correlated with the SiO2 content. Thus, the Xiabie Co granite is a weakly peraluminous I‐type granite belonging to the high‐K calc‐alkaline to Shoshone series. It is enriched in light rare earth elements (LREEs) and relatively depleted in heavy rare earth elements (HREEs), with LREE/HREE ratios of 8.03–16.40 and LaN/YbN ratios of 10.2–27.1. Samples show right‐leaning chondrite‐normalized rare earth element patterns with pronounced negative Eu anomalies (Eu/Eu∗ = 0.67–0.76). The primitive‐mantle‐normalized trace element spider diagrams of the samples are right‐leaning zigzag curves, showing relative enrichment in large‐ion lithophile elements (LILEs, e.g., Rb, Th, U, and K) and depletion in high‐field‐strength elements (HFSEs, e.g., Nb, P, Ti, and Yb) and displaying striking Sr and Ba negative anomalies. The granite εHf(t) values were positive (2.9–9.9), whereas the whole‐rock εNd(t) values were negative (–2.841 to –2.33). The calculated (87Sr/86Sr)t, (206Pb/204Pb)t, (207Pb/204Pb)t, and (208Pb/204Pb)t values are 0.7014–0.7057 (0.7044 on average), 18.422–18.851 (18.670 on average), 15.625–15.642 (15.633 on average), and 38.332–38.681 (39.571 on average), respectively. On the basis of the aforementioned data, we propose that the Xiabie Co granite was derived from a primitive magma that originated from partial melting of juvenile lower crust with the addition of mantle materials. In addition, strong fractional crystallization occurred during the rock‐forming process. Given the geodynamic setting, our new data, together with previously reported achievements, imply that the Xiabie Co granite was formed during the LS–QT collision.

Petrogenesis and Geodynamic Implications of Early Cretaceous (∼130 Ma) Magmatism in the Baingoin Batholith, Central Tibet: Products of Subducting Slab Rollback

“…The Mugagangri Group comprises sandstone, shale deposited in a bathyalabyssal environment and a small amount of basalt Zeng et al, 2016). After decades of research, it is generally accepted that the BNTO initially opened between the early Permian to Early Jurassic and finally closed at some point from the Middle Jurassic to Late Cretaceous (e.g., Guynn et al, 2006;Zhu et al, 2013Zhu et al, , 2016Fan et al, 2015;Li et al, 2016;Wang et al, 2018;Hu et al, 2020;Sun et al, 2020b;Huang et al, 2021;Liu et al, 2022).…”

Extensive Resetting of Feldspar Pb Isotopic Composition in Archean–Paleoproterozoic Granitic Rocks from the Kongling Terrane, South China: Implications for Tracing Thermal Evolutionary History

“…Pb isotopes have widely been used as isotopic tracers for the sources of magma, ore deposits, sediments, surface water and aerosols (Rudnick and Goldstein, 1990;Pettke et al, 2010;Bellucci et al, 2011;Xu and Jiang, 2017;Johnson et al, 2018;Liu et al, 2022). Pb-Pb isochrons can provide geochronological constraints for ancient terrestrial and extraterrestrial samples; for instance, they have been used to estimate the ages of meteorites and Earth (Patterson, 1956).…”

Petrogenesis and tectonic environment of the Middle Permian Luerma igneous complex in the southern Lhasa subterrane, Tibet: Evidence from geochemistry; Rb–Sr, Sm–Nd, and Lu–Hf isotopes; and zircon U–Pb geochronology

“…The closure of these basins was accompanied by the northward assembly of Gondwana‐derived terranes and the formation of the Tethyan Orogenic Belt (Dan et al, 2019; Dan et al, 2020; Metcalfe, 2013; Ouyang et al, 2019; Peng et al, 2013; Zeng et al, 2019), and the formation of the Tibetan Plateau (TP) was a key part of this process. The TP is mainly composed of four nearly parallel terranes, which are, from north to south, the Songpan–Ganzi terrane (SG), Qiangtang terrane (QT), Lhasa terrane (LS) and Himalayan terrane (HM) (Cao et al, 2022; Cao, Li, & Xia, 2021; Cao, Li, Zhang, et al, 2021; Dan et al, 2018; Li et al, 1995; Liu, Li, Huang, Zhang, Lü, et al, 2019; Liu, Li, Li, Huang, Li, et al, 2022; Liu, Li, Li, Li, Huang, et al, 2022; Xu et al, 2020). These terranes are divided by the Sanjiang orogenic belt (SJ), Bangong–Nujiang Suture Zone (BNS) and Yarlung–Tsangpo Suture Zone (YTS) (Dong et al, 2021; Huang, Ren, et al, 2021; Kong et al, 2016; Zhang et al, 2022) (Figure 1a).…”