LA-ICP-MS zircon U-Pb dating of the granitic and granodioritic porphyries from the Yanyingzui W-Mo-Cu polymetalic ore district in Fuchuan area, Guangxi, and its geological implications

Abstract：The Yangyingzui W-Mo-Cu polymetallic deposit is located in the middle segment of the northeast Guangxi metallogenic belt. Orebodies occur within the porphyry and skarn of the contact zone, and mineralization is closely related to the Yanyingzui porphyry. Up till now, however, there have been no precise data concerning the porphyry mineralization age of this ore deposit. The authors conducted the LA-ICP-MS zircon U-Pb chronologic study of the mineralized granite porphyry and granodiorite porphyry in the Yanyingzui W-Mo-Cu deposit and obtained ages of (426.2±2.3) Ma and (426.9±2.3) Ma, indicating that the porphyry is a product of tectonic-magmatic activity during the Caledonian. Combined with regional tectonic evolution, contrastive study of the timing for diagenesis and mineralization as well as geological characteristics of ores, it is suggested that the ore-forming and igneous activities of the Yangyingzui W-Mo-Cu polymetallic deposit occurred during Late Silurian, when the tectonic setting of the deposit was in the transition period from collision orogeny compression to extension. The Yangyingzui W-Mo-Cu polymetallic deposit has the same metallogenic age and same structural setting as the northeast Guangxi W-Mo mineralization belt, implying that the probable existence of an intense W-Mo-Cu mineralization during Caledonian period in northeast Guangxi. In addition, the NE-trending tectonomagmatic belt, the porphyry body zone and the periphery of the mineralization area are favorable areas in search for porphyry-skarn-type W-Mo-Cu polymetalic deposits, homologous series deposits and conceaned ore deposits, and hence more attention should be paid to the exploration and evaluation of the study area in the future.