LA-ICP-MS U-Pb dating of zircons from Guangshan and Zhaxi plutons in Shaoxing area, Zhejiang Province: constraint on the ore-forming epoch of the Lizhu iron ore deposit

The LA-ICP-MS U-Pb dating of zircons was carried out for two representative rock samples from Guangshan and Zhaxi plutons, which are closely related to mineralization of the Lizhu iron ore deposit. Based on the obtained results and regional chronologic data of mineralization, this paper has dealt with the mineralization age of the Lizhu iron ore deposit. The samples from Zhaxi pluton yielded the age of 150.1±2.6Ma, which is interpreted as its petrogenic age, and the sample from Guangshan pluton shows a number of magmatic events, with the main petrogenic age 147.2±1.7Ma, suggesting that both plutons belong to Yanshannian granitoids. Geological features of the Lizhu iron ore district show that mineralization of the Lizhu iron ore deposit was closely related to the magmatic hydrothermal event of Guangshan and Zhaxi plutons. In other words, the formation age of Guangshan and Zhaxi plutons represents the ore-forming age of the Lizhu iron ore deposit, i.e., Lizhu iron ore bodies were formed in Jurassic (~150Ma). Precise mineralization age of the Lizhu iron ore deposit plays a guiding role in search for the same type of ore deposits in adjacent areas.