Earth Science Frontiers ›› 2024, Vol. 31 ›› Issue (2): 224-248.DOI: 10.13745/j.esf.sf.2023.2.62

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Petrogenesis and tectonic significance of Caledonian I-Type granitoids in the Gulong and Liandong plutons in southeastern Guangxi

ZHOU Yuxi1,2(), SHI Yu1,2,*(), HUANG Chunwen3, LIU Xijun1,2, LAN Yuanchun1,2, TANG Yuanyuan1,2, WENG Boyin1,2   

  1. 1. Guangxi Key Laboratory of Hidden Metal Mineral Exploration, Guilin University of Technology, Guilin 541004, China
    2. Collaborative Innovation Center for Exploration of Nonferrous Metal Deposits and Efficient Utilization of Resources in Guangxi, Guilin University of Technology, Guilin 541004, China
    3. Hezhou Information Network Center of Science and Technology, Hezhou 542800, China
  • Received:2022-08-29 Revised:2023-01-26 Online:2024-03-25 Published:2024-04-18

Abstract:

The Early Paleozoic Caledonian orogeny caused extensive magmatic activities in the South China Block (SCB), but its tectonic attribute is still controversial over weather it was subduction collisional or intracontinental. Study on the petrogenesis of I-type granites in the Qin-Hang junction zone is of great geological significance to reveal the Early Paleozoic geodynamic background and tectonic evolution in southeastern Guangxi. In this study, whole-rock geochemical analysis, LA-ICP-MS zircon U-Pb dating and Lu-Hf isotope analysis of granite samples from the Liandong and Gulong plutons in southeastern Guangxi are carried out. The two plutons are granodioites with similar formation ages, at 435-434 and 436-435 Ma, respectively, and with similar geochemical characteristics (10000Ga/Al value of 2.07; (Zr+Nb+Ce+Y) content of 183×10-6; A/CNK ratio of 0.87-1.1, averaging 0.97; εHf(t) value of -2.2-1.8, mostly between 0-2; TDM2 age of 1.6-1.2 Ga, with a peak at 1.5-1.3 Ga; Nb/Ta ratio of 11.47-14.66, averaging 12.80; Rb/Sr ratio of 0.22-0.52), indicating both are calc-alkaline I-type granite originated from the partial melting of Mesoproterozoic meta-igneous rocks, probably containing some mantle-derived materials. A pluton formation model is proposed as follows: Large-scale collision between the southern SCB and the northern Gondwana margin created S-N and E-W stresses to the SCB triggering intracontinental orogeny. The thickened lithosphere underwent post-orogenic extension and thinning, and upwelling of mantle materials provided heat for the partial melting of the lower crust, forming the parental magma of the melting-type newborn crust (e.g. the Gulong pluton) or the mixed melting-type newborn crust with ancient crust component (e.g. the Liandong pluton). Under extensional environment after the intracontinental orogenic period, the parental magma upwelling along the channel formed the I-type granite with subduction-collision characteristics.

Key words: Caledonian, granitoids, geochemistry, zircon U-Pb dating, zircon Lu-Hf isotopes, southeastern Guangxi

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