Zircon fission track(ZFT) age of the Longxianggai pluton in Dachang of Guangxi and its geological significance

The Dachang polymetallic orefield in Guangxi is a world-class superlarge tin polymetallic deposit and the second largest tin production base in China.As the largest pluton in this area, Longxianggai pluton is closely related to mineralization.In this paper, zircon fission track dating method was used to restrict the time limit of multi-episode magmatic intrusion activity and explore its temporal and spatial relationship with mineralization.The results show that the zircon fission track ages of the Longxianggai pluton range from 160 Ma to 70 Ma, and can be divided into several age groups, i.e., 160~150 Ma, 120~100 Ma and 90~70 Ma, respectively.It obviously has three stages of thermal history, which reveals that the formation of Longxianggai pluton experienced three stages of magmatic intrusion.The metallogenesis of the Dachang polymetallic orefield was related to the granite emplacement during the lithospheric extension period under the influence of the subduction of the 120~100 Ma circum-Pacific plate in the Early Cretaceous(120~100 Ma).Magmatic intrusion activity not only provided the initial thermal fluid with some tin bearing polymetallic and volatile gases favorable for the activation and migration of ore-forming elements but also provided strong thermal energy and necessary physicochemical conditions for the migration and enrichment of ore-forming materials in the lower strata of early mineralization.