Tectonic geochemical characteristics of Lannigou Carlin-type gold deposit in southwestern Guizhou: Implications for downward extension of faults

The Lannigou Gold Deposit, located in the Yunnan−Guizhou−Guangxi "golden triangle" region, is one of the largest Carlin-type gold deposits in China. The formation of this gold deposit is closely related to tectonic activity, which is one of the key factors in gold mineralization. Although previous studies have extensively investigated the structure of Lannigou Gold Deposits, due to the lack of effective methods, issues such as how the ore-controlling faults extend downward, especially in cross-section, and the pathways and sources of fluid migration remain to be effectively resolved. To address these issues, this study integrated geophysical exploration data to conduct systematic structural-geochemical investigations on six major fault zones （Lannigou−Weihuai, Bianjie, Banchang, Luodun, Xinzhai, and Xiaonajing faults）. It deciphered fluid migration trajectories and material provenance through analysis of element migration-enrichment patterns. Innovative findings include: Comparison of geochemical characteristics reveals significantly stronger anomalies along the Bianjie and Lannigou−Weihuai faults than in Xinzhai and Luodun faults. The content variations of major elements such as Al₂O₃, Fe₂O₃, and P₂O₅ show indicative relationships with ore-forming elements including Sb. The results of multivariate statistical analysis show that elements such as Ni, Cd, and Tl exhibit a significant positive correlation with Au. Meanwhile, the trace element assemblage of Be, Bi, Cu, and Cr can serve as effective geochemical indicators for the mineralization of Au, Pb, Zn, and Sb. The coupling analysis of seismic exploration data and surface geochemical characteristics indicates that the Lannigou−Weihuai Fault and the Bianjie Fault have cut into the basement strata. The significant major and trace element anomalies in their tectonites are consistent with the characteristics of deep fluid activity. In contrast, the Banchang Fault and the Luodun Fault only developed within the shallow cover strata, and their geochemical anomalies are relatively weak in intensity. The spatial distribution of orebodies is strictly controlled by deep-seated large faults, and the Au and Sb anomaly intensities in tectonites show a positive correlation with fault incision depth. This finding provides a new technical approach for replacing costly deep geophysical exploration with surface geochemical exploration.