Two Nb-Ta mineralization events coeval with the metallogeny of Gongchangling iron ores in the North China Craton: Constraints from geochronology of the columbite-group minerals

Gongchangling iron deposit is famous for its large amount of high-grade magnetite ore, thus most of the researches focused on Gongchangling mining area Ⅱ due to the bulky high-grade iron ore. In this study, the U-Pb dating of the columbite-group minerals from the hanging wall granite in Gongchangling mining area Ⅰ yields two ages, i.e., 2501 ± 14 Ma and 1845 ± 20 Ma. The chemical compositions of the columbite-group minerals of both ages are always characterized by Nb > Ta, Fe > Mn, low U/Th, and relatively enriched HREE_N content, in consideration of the regionally ∼1.85 Ga mono- and multi-mineral uranium mineralization, the rare metal mineralization should be of NYF-type. The ∼2.50 Ga mineralization is coeval with the Lijiapuzi pegmatite Nb-Ta deposit, indicative of the excellent regional late Neoarchean Nb-Ta mineralization potential in eastern Liaoning Province; the ∼1.85 Ga event of Nb-Ta mineralization suggests that the widespread Paleoproterozoic plutons within Jiao-Liao-Ji belt and Trans-North China Orogen should be concerned in the near future. The intimate spatiotemporal relationship implies that the Paleoproterozoic Nb-Ta mineralization and the high-grade iron ores in the Gongchangling deposits were probably the products of the same geologic process, providing critical insights into the ore-forming process of both deposit types.