Genetic Mineralogical Study of the Cryptoexplosive Breccia in Tazigou, Northern Taihang Mountains

The Taihang Mountains Polymetallic Metallogenic Belt is an important Mesozoic magmatic-hydrometal metallogenic belt, and the cryptoexplosive breccia pipes within it are significant ore-hosting structures with important implications for mineralization. Based on zircon U-Pb geochronology, Lu-Hf isotopes, and genetic mineralogical studies of zircon and biotite from the monzogranite, which constitutes the main lithology of the cryptoexplosive breccia pipe in Tazigou, Tang County, Hebei Province, the following understandings have been obtained: Zircon U-Pb dating of the monzogranite yields an age of (117.2±1.2) Ma, indicating Early Cretaceous emplacement; The source region involves mixing of juvenile mantle-derived materials with ancient crustal components; Zircon morphological typology evolutionary trends reveal magma evolution from hybrid sources toward crustal domains, implying deep magma chambers experienced crustal assimilation or fractional crystallization, which facilitated preferential enrichment of metallogenic elements at shallow levels. Zircon crystallization temperatures (632.75 ℃ to 815.73 ℃) and oxygen fugacity values \lg f_\mathrmO_2 = –16.69 to –5.00; ΔFMQ = –1.75 to +9.16), combined with biotite crystallization temperatures (717.50 ℃ to 729.84 ℃) and host magma \lg f_\mathrmO_2 (–16.35 to –16.02), reflect a high-temperature, high-oxygen fugacity environment conducive to metallogenic element transport. Biotite exhibits hybrid crust-mantle signatures (I_Mg(Mg/(Fe+Mg))=(0.55 to 0.58)>0.5), classifying as magnesian biotite. The log(f_\mathrmH_2\mathrmO /f_HF)_fluid value ranges from 1.38 to 1.63 and the log(f_\mathrmH_2\mathrmO /f_HCl)_fluid value ranges from 4.11 to 4.65, indicating enrichment in volatiles during the late magmatic stage, creating favorable conditions for hydrothermal mineralization. Integrating the continental margin arc setting, hybrid crust-mantle magmas, cryptoexplosive breccia-hosted mineralization spaces, and high oxygen fugacity coupled with volatile-rich signatures, the study area is interpreted to possess significant potential for magmatic-hydrothermal copper-gold polymetallic mineralization.