implications from zircon U-Pb ages and Hf isotopic constraint on ore-forming granites in Youmaling and Jiepai deposits

Abstract：Youmaling and Jiepai are two newly-discovered tungsten-tin polymetallic deposits with middle-scale metal resources. Their main ore bodies occur in skarn and fractured rocks adjacent to the fine to medium grained monzogranite contacts. In this paper, in situ LA-MC-ICP-MS technology was employed to measure the U-Th-Pb and Hf isotopes of these granites from inner contacts of the Youmaling and Jiepai deposits. Zircon U-Pb isotopic results show that the granites were formed at Ca. 220±1 Ma (MSWD=0.035) and 215±1 Ma (MSWD=0.055) respetively, indicating that Indosinian metallogentic activity took place in Yuechengling-Miaoershan area. εHf(t) values of granite from Youmaling vary between -2.47 and -6.67, and those from Jiepai vary between -3.52 and -6.79, suggesting that they were both remelted from crust rocks. In contrast to other tungsten mineralized granites in the Nanling Mountains, the sources of two granites have higher εHf(t) values. A appropriate reason is that some Neoproterozoic island arc materials with positive εHf(t) values were involved during the remelting of the source materials. Isotopic ages from this paper and previous work indicate that intense Indosinian petrogenetic and metallogentic activities took place in this area. As we all know, fruitful exploration achievements have been obtained in the vicinity of contacts of Indosinian granites in the Nanling Mountains, so more attention must be paid to the exploration and evaluation in this area in the next few years.