New geochronological data from the Paleozoic and Mesozoic nappe structures, igneous rocks, and molybdenite in the North Wuyi area, Southeast China

摘要

The Wuyishan metallogenic belt, a part of the circum-Pacific tectonomagmatic belt, is considered one of the 19 key metallogenic belts in China because of its abundant mineral resources and vast prospecting potential. Specifically, the North Wuyi area is an important Cu-Pb-Zn polymetal ore-concentrated district in East China. We report new geochronological dates in this area, which suggest that the formation of mineralization-related magmatic rocks have mainly occurred during the Paleozoic and Mesozoic in four stages: the Caledonian (530Ma to 430Ma), Early-Middle Jurassic (183Ma to 160Ma), Early Cretaceous (140Ma to 110Ma), and Late Cretaceous (63Ma to 85Ma). The mineralization events are either coeval or slightly postdate the related magmatic activities. Nappe structures are widespread in the North Wuyi area and play an important role in the formation and preservation of ore deposits, as determined from field observations and structural analyses of mining tunnels. The regional distribution and structural styles of the thrust faults in the North Wuyi area and new ~(40)Ar- ~(39)Ar dating results (415Ma to 390Ma) confirm that intensive tectonic activity during the Early Paleozoic, when the South China Block was about to separate from Gondwana, has wiped out evidence of Caledonian mineralization. All nappe structures with regional scales (several thousand meters) were formed during the Early Cretaceous period, with an ~(40)Ar- ~(39)Ar age of 120Ma to 129Ma. The thrust direction of the nappe structures is mainly southeast during the Early Cretaceous in the main body and north piedmont of the Wuyi Mountain. These early thrust faults have not only broken or reformed the existing ore deposits, but have also provided hydrothermal ore-forming channels and spaces for metallogenism that are coeval or posterior to the thrust. The subsequent nappe structures thrust mainly from southeast to northwest and overprint the previous southeastward thrust faults. Using ~(40)Ar- ~(39)Ar dating of the structural belt, U-Pb SHRIMP zircon dating of the wall rocks, and Re-Os dating of the ore formation, we analyze the genetic connection between the structures and ore bodies in different ore fields. Our results serve as useful information on prospecting for the latent ore body in the North Wuyi area, especially the ore bodies destroyed by faulting activities.