Gan Jie, Wang Wei, Yan Dongdong, Zhou Hu, Xiong Fuhao, Zhou Huailai, Li Hui
State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Chengdu University of Technology, Chengdu, 610059, China.
Geological Resources and Geological Engineering Postdoctoral Workstation, Chengdu University of Technology, Chengdu, 610059, China.
Sci Rep. 2025 May 2;15(1):15418. doi: 10.1038/s41598-025-99076-8.
Understanding the petrogenetic relationships among the synplutonic dikes, magmatic enclaves and plutons in subduction zones provides key insights into the petrological diversity of arc magmatism. Here we present an integrated study on the petrology, LA-ICP-MS zircon U-Pb geochronology, whole-rock geochemistry and Sr-Nd-Hf isotopes of Triassic coeval basic-intermediate dikes, mafic microgranular enclaves (MMEs) and their host plutons (gabbrodiorite, granodiorite and monzogranite) in the East Kunlun Orogen, northern Tibetan Plateau, to reveal their magma sources, magmatic processes and dynamic connections. Petrological and chronological studies reveal that these mafic-felsic igneous rocks coexist in space and time, showing imprints of mixing or mingling and similar crystallization ages (ca. 248-242 Ma), forming a typical synplutonic complex. Geochemically, the synplutonic complex shows continuous compositional variations with varying SiO (44.22-76.56 wt%), whole-rock Sr-Nd and zircon Lu-Hf isotopic compositions ((Sr/Sr) = 0.707521 to 0.717628, εNd(t) = -6.66 to 1.84, εHf(t) = -7.86 to 2.73). Petrogenetic research indicates that crust-mantle magma mixing and fractional crystallization respectively play crucial roles in their petrological and geochemical diversity. The mantle-derived mafic end-member, represented by the mafic dikes, originated from the partial melting of the sub-arc mantle wedge that metasomatized by subduction-related fluids. The crust-derived felsic end-member, represented by the monzogranite pluton, was sourced from the Mesoproterozoic metapelite-like continental basement of the East Kunlun Orogen. The mantle-derived mafic magma underplated the felsic lower continental crust, triggering its melting to form the felsic magmatic end-member. Subsequently, the crust-mantle magma end-members interacted mechanically or chemically in various proportions, forming the parental magmas of the cogenetic MMEs, intermediate dikes and gabbrodiorite to granodiorite plutons. This study demonstrates that mechanical or chemical mixing and subsequent fractional crystallization of crust-mantle magmas are significant mechanisms responsible for the petrological and geochemical diversity of continental magmatic arcs.
了解俯冲带中同深成岩脉、岩浆包体和深成岩体之间的岩石成因关系，可为深入了解弧岩浆作用的岩石学多样性提供关键线索。在此，我们对青藏高原北部东昆仑造山带三叠纪同期基性-中性岩脉、镁铁质微粒包体（MMEs）及其寄主深成岩体（辉长闪长岩、花岗闪长岩和二长花岗岩）进行了岩石学、LA-ICP-MS锆石U-Pb年代学、全岩地球化学以及Sr-Nd-Hf同位素的综合研究，以揭示它们的岩浆源区、岩浆过程和动力学联系。岩石学和年代学研究表明，这些镁铁质-长英质火成岩在空间和时间上共存，显示出混合或混染的印记以及相似的结晶年龄（约248 - 242 Ma），形成了典型的同深成杂岩体。地球化学上，该同深成杂岩体显示出连续的成分变化，SiO含量在44.22 - 76.56 wt%之间，全岩Sr-Nd和锆石Lu-Hf同位素组成分别为((Sr/Sr)=0.707521至0.717628，εNd(t)= -6.66至1.84，εHf(t)= -7.86至2.73)。岩石成因研究表明，壳幔岩浆混合和分离结晶分别在其岩石学和地球化学多样性中起关键作用。以基性岩脉为代表的幔源镁铁质端元源自受俯冲相关流体交代的弧下地幔楔的部分熔融。以二长花岗岩体为代表的壳源长英质端元源自东昆仑造山带中元古代类泥质岩大陆基底。幔源镁铁质岩浆底侵到长英质下地壳，引发其熔融形成长英质岩浆端元。随后，壳幔岩浆端元以不同比例进行机械或化学相互作用，形成了共生MMEs、中性岩脉以及从辉长闪长岩到花岗闪长岩深成岩体的母岩浆。这项研究表明，壳幔岩浆的机械或化学混合以及随后的分离结晶是造成大陆岩浆弧岩石学和地球化学多样性的重要机制。
