Monazite U-Pb Chronology, Pyrite Rb-Sr Chronology and Isotope Geochemistry of the Xidouya Gold Deposit in the Jiaodong Peninsula, Eastern China: Constraints on the Timing and Process of Mineralization

The Jiaodong gold concentration area, one of the most important gold metallogenic belts in China, has long been the focus of contentious debates regarding the genetic mechanisms and timing of gold mineralization. This study presents the new monazite U-Pb and pyrite Rb-Sr isotopic chronology data for the No. I ore zone of the Xidouya gold deposit, integrated with H-O-S isotopic geochemical analyses, to systematically investigate the mineralization age, ore-forming fluid sources and material provenance of the deposit. The main mineralization age of the deposit is constrained to 117 Ma, which is highly consistent with the regional mineralization peak of 120 ± 5 Ma in the Jiaodong gold concentration area. The δD values of the fluids range from −88.0‰ to −75.0‰ (mean = −82.6‰), while the δ18OH2O values are calculated to be between 4.6‰ and 6.1‰. H-O isotopic data indicate that the ore-forming fluids of the Xidouya gold deposit originated from a mixed magmatic and meteoric source. As mineralization progressed from Stage I through Stage III, there was a detectable trend of increasing meteoric water involvement and a general decrease in δD and δ18OH2O values. This signature indicates that the initial mineralizing system was dominated by primary magmatic water which subsequently underwent significant water–rock interaction with Early Cretaceous granitic bodies and progressive dilution by meteoric fluids in an open tectonic environment. Furthermore, sulfur isotopes (average δ34S = +7.43‰) and the initial strontium isotope ratio (87Sr/86Sr = 0.71012) support a mixed-source model for the ore-forming materials, likely dominated by the anatexis of ancient crust with potential minor mantle-derived contributions. During the Early Cretaceous, lithospheric thinning and extension in the North China Craton (NCC) triggered large-scale magmatism and mineralization. The Xidouya gold deposit is a direct product of these regional tectono-magmatic-mineralizing events. This study provides new high-precision isotopic dating data for the Xidouya gold deposit, clarifies the evolutionary history of ore-forming fluids and the supply mechanism of ore-forming materials, and provides important theoretical insights and practical references for gold prospecting and exploration in the eastern part of the Jiaodong gold concentration area.