Late Cretaceous Sn-W mineralization along the northeastern margin of the Laojunshan granite complex in the southeastern Yunnan Sn-W belt, SW China

• Tin-W mineralization was formed in the Late Cretaceous. • Tin-W mineralization is genetically associated with the third stage of granite. • Four stages of Sn-W mineralization developed in the Laojunshan district. The Laojunshan Sn–W polymetallic ore district (LPD), situated in the eastern part of the southeast Yunnan Sn–W belt, is one of China’s significant Sn-W mineralization-rich areas. Numerous Sn-W deposits (e.g., the Wazha, Caoguoshan, and Dongfei) are distributed along the northeastern margin and within the Laojunshan granite complex. The Sn–W mineralization occurs in the form of quartz ± ore minerals (wolframite/scheelite, and/or cassiterite) ± sulfide vein. However, the genetic relationship between these Sn-W deposits and Laojunshan granite complex remains unknown. In this study, detailed in situ U–Pb dating was performed on the zircon grains from ore-hosting granite (Dongfei deposit) and the wolframite and cassiterite collected from the Dongfei, Caoguoshan, and Wazha deposits. The wolframite and cassiterite samples from the Caoguoshan deposit yield ages of 81.9 ± 2.3 Ma and 82.3 ± 0.71 Ma, respectively. The cassiterite and wolframite samples from the Dongfei deposit yield ages of 82.0 ± 2.3 Ma and 81.3 ± 2.5 Ma, respectively. The wolframite samples from the Wazha deposit have ages of 80.9 ± 1.8 Ma, while zircon grains from the granite of the Dongfei deposit yield ages of 87.8 ± 0.4 Ma and 87.6 ± 0.4 Ma. The geochronology data and spatial relationship imply that these three Sn-W deposits formed in the Late Cretaceous (83 to 80 Ma) and are genetically associated with the third stage of the Laojunshan granite complex (84–80 Ma). These new age data combined with previous age results, we categorize the mineralization event in the LPD into four major metallogenic stages: the first stage (445–388 Ma), the second stage (230–203 Ma), the third stage (160–140 Ma), and the fourth stage (97–79 Ma). The fourth stage of mineralization is most widely distributed Sn-W mineralization in the Laojunshan district, which can be subdivided into three sub-stages, including ca.97–88 Ma, 87–85 Ma, and 84–79 Ma. The Late Cretaceous Sn-W mineralization events in this region occurred during a period of regional extension. This study highlights the great potential for the formation of Late Cretaceous Sn-W deposits along the northeastern margin of the laojunshan granite complex.