关键词: 石英闪长玢岩；锆石U-Pb定年；微量元素')">

石英闪长玢岩；锆石U-Pb定年；微量元素,  ')">地球化学；北武夷成矿带；斑岩型铜矿

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Abstract: The North Wuyi metallogenic belt is one of the important polymetallic metallogenic belts in South China, and its Yanshanian magmatism is closely related to copper polymetallic mineralization. The Huangshiqiao area is located on the northern margin of the eastern segment of this belt, between the Chuankeng and Tongshan copper deposits. However, the chronology and petrogenesis of the quartz dioritic porphyrite in this area remain poorly constrained, which restricts the understanding of regional metallogenic regularity. In this study, LA-ICP-MS zircon U-Pb dating and in-situ zircon trace element analyses were performed on the Huangshiqiao quartz diorite porphyry to precisely determine its emplacement age, classify its petrogenetic type, reveal the nature of Cu-rich magma, and evaluate its metallogenic potential. The results show that the weighted mean zircon U-Pb age is (170.6±2.4) Ma, corresponding to the Middle Jurassic, and is nearly contemporaneous with the Chuankeng quartz monzonite porphyry (170.0±1.0) Ma and the Tongshan granodiorite porphyry (171.0±1.6) Ma. Zircons exhibit magmatic characteristics with oscillatory zoning, with Th/U ratios ranging from 0.18 to 0.53. Their rare earth element (REE) patterns are characterized by enrichment in heavy REEs (HREEs) and weak negative Eu anomalies (Eu/Eu*=0.63-0.85). The average zircon Ti-saturation temperature (T) is 706 °C. The deviation of oxygen fugacity from the fayalite-magnetite-quartz (FMQ) buffer (ΔFMQ) is 0.63, and the logarithm of oxygen fugacity (lg (O2)) is-16.37. These magmatic oxygen fugacity data indicate that the porphyrite formed in a post-subduction extensional setting related to the subduction of Paleo-Pacific Plate, and was derived from partial melting of thickened lower crust with mantle contribution. Zircon Ce/Nd ratios (average 18.46) and Ce4+/Ce3+ ratios (average 297.23) suggest that the magma had relatively high oxygen fugacity, consistent with the characteristics of ore-forming intrusions in porphyry copper deposits, indicating porphyry copper metallogenic potential. Based on the regional metallogenic conditions and the nature of Cu-rich magma, the Huangshiqiao quartz dioritic porphyrite and its adjacent areas have considerable prospects for porphyry copper exploration.

Key words: quartz diorite porphyry, zircon U-Pb dating, trace element, geochemistry, Northern Wuyi metallogenic belt, porphyry copper deposit