The syncollisional granitoid magmatism and crust growth during the West Qinling Orogeny, China: Insights from the Jiaochangba pluton

Abstract

The West Qinling Orogenic Belt (WQOB) is a major portion of the Qinling‐Dabie‐Sulu Orogen and holds essential information for understanding the protracted evolution of the north‐eastern branch of the Paleo‐Tethys in East Asia. In this study, we report our petrological, geochemical, and geochronological study on the five Triassic granitoid plutons of West Qinling with emphasis on the poorly studied Jiaochangba pluton with zircon U–Pb ages of 217.5 ± 1.6 Ma and 215.2 ± 1.2 Ma. The new data and the existing data on the other four plutons support the view that the West Qinling granitoids represent a magmatic response to the continental collision of the Yangtze Block (YB) with the North China Craton (NCC) in the Triassic. Like the other four plutons, the Jiaochangba pluton shows strong light rare earth element (REE) enrichment and weak heavy REE depletion ([La/Sm]N ≈ 7.14 ± 1.89; [Sm/Yb]N ≈ 4.63 ± 1.85) with varying negative Eu anomalies (Eu/Eu* ≈ 0.65 ± 0.20). In the N‐MORB normalized diagram, all the samples show relative enrichment in Rb, Pb, U, and K with negative Nb, Ta, P, and Ti anomalies, resembling those of the model continental crust. The Jiaochangba pluton has relatively lower (87Sr/86Sr)i (0.7062 to 0.7081), higher εNd(t) (−6.91 to −2.09), and εHf(t) (−5.57 to −0.14) than mature continental crust, which are consistent with their source being dominated by lower crust with significant mantle contributions. Mantle‐derived melt, which formed from partial melting of mantle wedge peridotite facilitated by dehydration of the subducted/subducting Mianlue ocean crust, provide the required heat for the crustal melting while also contributing to the compositions of these granitoids. Evolution of such parental magmas in open system crustal magma chambers with continued evolution/replenishment and crustal contamination and assimilation give rise to the observed petrological and geochemical characteristics of these granitoids.

A simple and robust method for calculating temperatures of granitoid magmas

“…In this section, we use bulk-rock major and trace element data of syn-collisional I-type granitoid samples saturated in zircon from the Qilian, Kunlun and Qinling Orogens in central and western China (Chen et al 2015(Chen et al , 2016Zhang et al 2015;Duan et al 2016;Li et al 2016Li et al , 2017 Zhang et al 2015;Duan et al 2016;Li et al 2016Li et al , 2017Kong et al 2017Kong et al , 2019Kong et al , 2020Shao et al 2017) et , 2020Shao et al 2017). In addition, we have collected granitoid data compiled through the Earth-Chem portal (http:// portal.…”

Petrology and geochemical characteristics of amphibolite facies rocks in Xunyangba area, South Qinling Orogen, Central China

“…After ~440 Ma, the YZB subducted toward the NCB and the SQO as a passive continental margin, which accepted the deposition of the early Devonian marine sediments. Afterward, the Mianlue Basin was closed in the Qinling Orogen in the late Triassic (~220-200 Ma) (Kong et al, 2017;Kong et al, 2019b), and the orogenic belt was uplifted to become mountains by comprehensive collision, and metamorphism occurred as the fourth stage. Finally, in the Meso-Cenozoic, with the effects of tectonic extrusion and strike-slip of the SQO, the basement rocks at the depths in the Xunyangba area were exposed to the surface.…”

Single-Grain Detrital Apatite Sr Isotopic Composition as an Indicator to Trace Sedimentary Sources: A Case Study of Sedimentary Rocks in the Hui-Cheng Basin, South Qinling, China

“…Figure 4. Age histogram of detrital zircon grains from Neogene and Jurassic conglomerate samples.Data sources: igneous rocks in the Qinling orogenic belt[23,33,36,[40][41][42][43][44][45][46][47][48].…”