Magmatism, geological setting, alteration, and metallogenic potential of Donghua area, Dehua County, Fujian Province, Southeast China: Insights from porphyry zircon U-Pb and pyrite Rb-Sr geochronology, geochemistry and remote sensing

Abstract Located in the southern section of the Wuyi Mountain metallogenic belt, the Dehua-Youxi-Yongtai (DYY) ore district is one of the potential areas of gold deposits in the Fujian province, Southeast China. Gold mineralization is widely distributed in this district, including Qiucun, Shuangqishan, Ancun, and Dongyang gold deposits. However, the DYY ore district is still at a low degree of exploration and research. This paper focuses on the Donghua area in the northwest of the DYY ore district as its typical and integrated volcano-magma mechanism revealed in this study. Combined approaches including zircon SHRIMP U-Pb geochronology, Rb-Sr isochron dating and mineral chemistry of pyrite, and hyperspectral remote sensing are employed, aiming to identify the magmatism, alteration, geological setting, and metallogenic potential of the Donghua area. The zircon SHRIMP U-Pb ages of the granite porphyritic dykes in Donghua are 154.6 ± 1.1 Ma and 153.2 ± 1.2 Ma, respectively, indicating that the dykes were formed in the late Jurassic. The Rb-Sr geochronological age of hydrothermal/epithermal pyrite in Donghua is 153.7 ± 2.4 Ma, which is almost coeval with that of the granite porphyritic dykes within error, and consistent with the regional volcanic-magmatic activity and the metallogenic age of the regional metallogenic event. The granitic dykes in Donghua exhibit the characteristics of both A-type and I-type granitoids, thus indicating the presence of transitional geochemical characteristics. As a result of the subduction of the Pacific Plate towards the Eurasia, the ca. 154–153 Ma magmatic event in the Donghua area occurred at the beginning of large-scale delamination of the continental crust. The zoning distribution of the mineral alteration of chlorite, dickite, kaolinite, and gypsum, the interpretation of volcanic activity from the annular structure of hyperspectral remote sensing, and the inferred deep-seated intrusion emplacing from northwest to southeast are in agreement, thus displaying the volcano-magma-alteration mechanism developed in the Donghua area. The magmatism, dykes, faults, and Neoproterozoic metamorphic rock provide favorable advantages for the mineralization in Donghua, suggesting metallogenic potential.