The 40Ar–39Ar dating of biotite in ore veins and zircon U–Pb dating of porphyrtic granite dyke in the Nanyangtian tungsten deposit in SE Yunnan, China

Abstract The Nanyangtian tungsten deposit is located in the Laojunshan Sn–W polymetallic metallogenic province in SE Yunnan, China. Tectonically it is located in the conjunction of the Cathaysia and Indochina blocks. The orebodies primarily hosted within the stratiform-like skarn and marble in the Paleoproterozoic Nanyangtian formation. Three ore-forming stages have been identified based on mineral assemblages and on the intercalated relationships between the veins.They include skarn-scheelite stage, quartz-scheelite vein stage and carbonate-scheelite vein stage. In this paper, we present 40Ar–39Ar laser incremental heating analyses of hydrothermal biotite intergrowth with scheelite from quartz-scheelite vein with two yielded well-defined 40Ar–39Ar plateau ages of 97.49±0.97 Ma and 99.48±0.97 Ma, and two isochronal ages of 97.01±1.39 Ma and 99.58±0.98 Ma, respectively, representing the age of second mineralization stage of the Nanyangtian tungsten deposit. The ages are well consistent with the emplacement age of the Laojunshan granite (96Ma to 117Ma). U–Pb geochronological data for magmatic zircons separated from porphyritic granite dyke in the mine pit indicate that the granite body was emplaced in the post-ore stage (89.88±0.53Ma). Integrated with previously high resolution diagenetic and metallogenic geochronological data, two significant magmatic-mineralization events are presented in SE Yunnan, China and North Vietnam. The first event took place from 97 Ma to 124 Ma, which is closely related to the tungsten mineralization. The second event occurred from 75 Ma to 95 Ma, which is closely related to the Sn–Cu–Ag–Zn mineralization. According to the exhibited data, we preliminarily conclude that the Late Cretaceous magmatic-mineralization activity in SE Yunnan and North Vietnam is the product of post-collision of the Cathaysia and Indochina blocks and should have formed under a same geodynamic setting.