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

Abstract

The Baingoin batholith is one of the largest granitic plutons in the North Lhasa terrane. Its petrogenesis and tectonic setting have been studied for decades, but remain controversial. Here we report data on geochronology, geochemistry and isotopes of Early Cretaceous granitoids within the Baingoin batholith, which provide more evidence to uncover its petrogenesis and regional geodynamic processes. The Early Cretaceous magmatism yields ages of 134.4–132.0 Ma and can be divided into I‐type, S‐type and highly fractionated granites. The I‐ and S‐type granites exhibit medium SiO2, high K2O/Na2O with negative εNd(t) and εHf(t) values, whereas, the albite granites have very high SiO2 (79.04%–80.40%), very low K2O/N2O, negative εNd(t) and a large variation in εHf(t). Our new data indicate that these granitoids are derived from unbalanced melting in a heterogeneous source area. The granodiorites involved had a hybrid origin from partial melting of basalt‐derived and Al‐rich rocks in the crust, the porphyritic monzogranites being derived from partial melting of pelitic rocks. The albite granites crystallized from residual melt separated from K‐rich magma within the ‘mush’ process and underwent fractionation of K‐feldspar. We believe that the Early Cretaceous magmatism formed in an extensional setting produced by the initial and continuous rollback of a northward‐subducting slab of the NTO.

Strongly Peraluminous Highly Fractionated I-Type Granite from Bangong–Nujiang Metallogenic Belt, Tibet: Implications for Continental Evolution and Evaluation of Economic Potentiality

“…However, the field investigation revealed that the Kese granite primarily comprises granite and overlaps with Diqian granodiorite without a clearly defined boundary (Figure 2a). Based on the zircon U-Pb dating results, we infer that Kese granite was formed later than Diqian granodiorite (~134.4 Ma) [37]. [34]; (b) modified after [23]; (c) age data from [23,35,[37][38][39][40]).…”

“…Based on the zircon U-Pb dating results, we infer that Kese granite was formed later than Diqian granodiorite (~134.4 Ma) [37]. [34]; (b) modified after [23]; (c) age data from [23,35,[37][38][39][40]).…”

“…Diqian granodiorite is emplaced at 134.4 Ma and adjacent to Kese granite (Figure 1). Due to the long emplaced interval (up to 6.4 Ma), it cannot be assumed that Kese granite was generated directly from the Diqian pluton via fractional crystallization [104], while Diqian granodiorite exhibits similarities with Kese granite in terms of whole-rock ε Nd (t) (−7.5~−7.1) and zircon ε Hf (t) (−3.2~−1.3) values [37]. Given the spatial relationship between the two plutons and their isotopic characteristics, it is plausible to conclude that Kese granite formed from the partial melting of the Diqian pluton followed by intensive fractional crystallization or shared a common magma source.…”

“…In a study based on Yanhu volcanic rocks, it was speculated that the ~130 Ma basaltic magma derived from the partial melting of a metasomatized mantle wedge formed the juvenile lower crust with positive whole-rock ε Nd (t) values [60,105]. Considering the scissor-like diachronous orogeny from east to west, this mafic magma event is likely to correspond to the 134.4 Ma magmatic event in Baingoin, which may be represented by the mafic microgranular enclaves (MMEs) present in Diqian granodiorite [37]. In this paper, we consider the known 130 Ma Yanhu basalt as mantle-derived magma and select the typical rocks derived from the ancient lower and middle-upper continental crustal materials [61,62].…”

Geochronology, Geochemistry and Petrogenesis of the Bangbule Quartz Porphyry: Implications for Metallogenesis

“…Strong Eu and Sr depletion (Fig. 8) requires extensive fractionation of plagioclase and/or K -feldspar (e.g., Hanson, 1978;Li et al, 2007;Li et al, 2022). The decreasing trends of TFe 2 O 3 and MgO concentrations with increasing SiO 2 (Fig.…”