Apatite u-pb Geochronology and pyrite geochemistry of the Hougou gold Deposit: Implications for Devonian gold mineralization in the Zhangxuan gold Belt, northern margin of the North China Craton

The Zhangxuan gold belt, situated along the northern margin of the North China Craton, remains a topic of debate concerning the genesis of its associated gold deposits. In this study, we integrate apatite U-Pb dating, pyrite geochemical and sulfur isotopic compositions of the Hougou deposit, a representative potassium-altered rock-type gold deposit in Zhangxuan gold belt, to constrain the timing and genesis of gold mineralization. Hydrothermal apatite, intergrown with pyrite, has a U-Pb age of 381 ± 15 Ma, indicating that the gold mineralization occurred in the Devonian. Three types of pyrite are identified in Hougou: Py 1 (K-feldspar–pyrite stage), Py 2 (Quartz–K-feldspar–pyrite stage), and Py 3 (Quartz–K-feldspar–polymetallic sulfide stage), among which Py 3 is closely associated with gold mineralization. All pyrite exhibit Co/Ni and Te/Au ratios > 1, and δ 34 S values ranging from −12.94 ‰ to + 5.10 ‰, consistent with those of the Zhangxuan gold belt, supporting a predominantly magmatic origin for the ore-forming fluids and sulfur sources. By comparing the geological characteristics of different types of gold deposits and pyrite geochemistry, we reveal that the composition of Au, Ag, Te, and Pb in pyrite from Hougou exhibit similarities to those of magmatic- hydrothermal deposits such as Dongping, Jiaodong-type and porphyry gold deposits, but has certain differences from orogenic and Carlin-type deposits. Therefore, we conclude that the Hougou gold deposit was initially linked to the magmatic-hydrothermal activity associated with the Devonian Shuiquangou alkaline intrusion, with overprinting during the Early Cretaceous.