ZIRCON U-Pb DATING OF MONZOGRANITE DIKES IN WENGQUANGOU BORON OREFIELD, EASTERN LIAONING: Constraints on Metallogenic Age

A monzogranite dike cuts through the ludwigite orebody in the open pit of Wengquangou boron deposit, Liaodong Peninsula. Samples of the dike are collected for thin section and zircon LA-ICP-MS U-Pb geochronology analysis. The monzogranite dike is characterized by high SiO₂ content(71.82%-75.68%) and high Na₂O+K₂O content (8.41%-10.57%), belonging to calc alkali-high K calc alkaline series granite. The zircon grains in the dikes are euhedral column in shape and dark in the CL image due to the high uranium content. The U-Pb upper intercept age is 1842±29 Ma, among which 9 testing points yield the weighted average age of 1842±30 Ma, indicating that the emplacement age of dike was Late Paleoproterozoic and the Wengquangou ludwigite deposit should be formed earlier. The age is consistent with the post-peak time of metamorphism in the Paleoproterozoic Jiao-Liao-Ji orogeny, reflecting the boron mineralization occurred during the process.