As China’s third-largest lead–zinc ore field, the Xicheng Ore Field has significant potential for discovering concealed deposits. In this study, a tectono-geochemical survey was conducted, and 1329 composite samples (comprising 5614 subsamples) were collected from the central part of the field. The dataset was analyzed using staged factor analysis (SFA) and concentration–area (C–A) fractal model. Four geochemical factors were extracted from centered log-ratio (CLR)-transformed data: F_2-1 (Ag–Pb–Sb–Hg), F_2-2 (Mo–Sb–(Zn)), F_2-3 (Au–Bi), and F_2-4 (W–Sn). Known Pb–Zn deposits coincide with positive F_2-1 and negative F_2-2 anomalies, as identified by the C–A fractal model, suggesting these factors are reliable indicators of Pb–Zn mineralization. Five Pb–Zn exploration targets were delineated. Statistical analysis and anomaly maps for F_2-3 and F_2-4 also indicate the potential for Au and W mineralization. Notably, some anomalies from different factors spatially overlap, indicating the possibility of epithermal Pb–Zn mineralization at shallow depths and mesothermal to hyperthermal Au and W mineralization at great depths. Overall, the integration of tectono-geochemistry, targeted and composite sampling, SFA, and C–A fractal modeling proves to be an effective and economical approach for identifying and enhancing ore-related geochemical anomalies.

Ultrapotassic lamprophyre dykes are spatially closely related to gold deposits in collision tectonic belts. However, the potential implication of these lamprophyre dykes to gold deposits remains poorly constrained. Abundant ultrapotassic lamprophyre dykes in the Baiyun gold deposit of Liaodong Peninsula, NE China, are closely associated with Au orebodies. This presents an excellent opportunity to investigate the genesis and tectonic significance of these dykes, as well as their potential connection to gold mineralization. Here, based on LA-ICPMS zircon U-Pb age, petrogeochemistry, and Sr-Nd-Hf isotopic composition characteristics, we studied the ultrapotassic lamprophyre dykes in the Baiyun gold deposit. Zircon U-Pb dating of lamprophyre dykes is 225.7 ± 1.3 Ma, which is consistent with the previous auriferous pyrite Re-Os data results within error, indicating that the lamprophyre dykes and gold deposits formed simultaneously in the Late Triassic, which coincided with the exhumation of the deeply subducted South Chin Block (SCB). The lamprophyre dykes belong to the shoshonitic series (K₂O + Na₂O = 6.39–7.57 wt.%, K₂O/Na₂O = 3.99–8.74) and are enriched with magnesium (MgO = 5.33–6.40 wt.%, Mg^# = 58–65), barium (Ba = 2225–3046 ppm), and strontium (Sr = 792–927 ppm), and their (⁸⁷Sr/⁸⁶Sr)_i isotopic composition ranges from 0.712514 to 0.714831, ε_Nd(t) ranges from −15.4 to −14.1, and zircon ε_Hf(t) values range from −14.3 to −12.5. These correspond to Paleoproterozoic model ages between 2.1 and 2.3 Ga, which are comparable to the ultra-high-pressure metamorphic rocks with the SCB nature found in the Dabie–Sulu orogenic belt. The results demonstrate that the overlying lithospheric mantle was possibly metasomatized by subducted SCB-derived melts before magma generation under the North China Block (NCB) in the Late Triassic. The lamprophyre dykes with high Nb/U and Th/Yb values, enriched Ba, Sr, REE, Na₂O + K₂O, K₂O/Na₂O, and the LOI demonstrate that the metasomatic agents were hydrous, high-pressure melts. These melts likely resulted from the partial melting of subducted continental crust, which is attributed to phengite breakdown in the subduction continental channel. The silica-rich melts migrate from the plate into the sub-continental lithospheric mantle (SCLM) and form potassic- and volatile-enriched metasomatized SCLM. Subsequently, the partial melting of metasomatized SCLM due to the decompression and thinning may be the main mechanism to generate the syn-exhumation ultrapotassic magma in a post-collision setting. This study suggests that the SCLM, metasomatized by melts derived from continental crust, plays a key role in generating volatile-rich hydrous SCLM during the continental subduction and collision stage. In contrast, during the post-collision stage, as tectonic forces transition from compressional to extensional, the abundant volatiles and ultrapotassic magma produced from the partially melted and metasomatized lithospheric mantle may significantly contribute to the transportation, enrichment, and precipitation of gold through magmatic-hydrothermal processes, facilitating the formation of gold deposits.