Geochronology and geochemistry of granitic dikes in the Xiaogushan gold deposit NE China and implications for gold mineralization.

The Xiaogushan cryptoexplosive breccia-type gold deposit is located within the eastern Hebei-western Liaoning gold belt along the northern margin of the North China Craton. The mining area contains multiple episodes of subvolcanic dikes, among which the granite porphyry and granitic aplite dikes show close temporal and spatial relationship with gold mineralization. To constrain their emplacement age, petrogenesis, tectonic setting, and metallogenic significance, integrated zircon U-Pb-Hf isotopic and whole‑rock geochemical analyses were carried out on these dikes. Zircon U-Pb dating yields emplacement ages of 163.9 ± 2.0 Ma for the granite porphyry and 162.2 ± 4.9 Ma for the granitic aplite, indicating Late Jurassic magmatism in the region. The rocks are enriched in SiO2, K2O, and LILEs, depleted in HFSEs, and classified as strongly peraluminous, high‑K calc‑alkaline S‑type granites. The primary magma, derived from Paleoproterozoic lower crust (εHf(t) = -17.7 to -13.5; TDM2 = 2.29 to 2.07 Ga), and the geochemical variations are consistent with fractional crystallization of K‑feldspar and plagioclase. Regional tectonic evidence indicates that these dikes were emplaced in a continental collisional setting related to the closure of the Mongol‑Okhotsk Ocean. This collision caused crustal thickening, deformation, and subsequent extension, which promoted mineralization. These dikes characterized by high oxygen fugacity, alkali enrichment, and moderate evolution, may facilitate metal transport and remobilize pre‑existing mineralization via associated hydrothermal systems. Their clustered occurrence thus serves as a potential indicator for deep‑seated hydrothermal activity and gold mineralization, reflecting the intense Mesozoic tectono-magmatic-metallogenic event in the northern North China Craton.