关键词: 四平山金矿床, 成矿作用, 成矿时代, 地球化学, 稳定同位素, 热水沉积

Abstract: Sipingshan gold deposit is located in the Wandashan epicontinental accretional terrane in eastern Heilongjiang, China. The ore bodies are mainly hosted in the Lower Cretaceous Sipingshan Formation, showing obvious two-stage mineralization. To further determine the mineralization and genesis of the deposit, this study analyzes its metallogenic geological characteristics, metallogenic chronology and source of metallogenic materials. The samples from the ore-related granite porphyry have relatively high SiO₂ (70.07%-72.93%) and （K₂O+Na₂O）(7.17%-8.42%), which belong to A-type granite. The ore-bearing siliceous rocks are characterized by Al/(Fe+Al+Mn)<0.32, Fe/Ti>20, (Fe+Mn)/Ti >20, Fe₂O₃ (0.18%-1.79%), FeO(0.17%-0.96%), MnO (0.03%-0.12%), TiO₂ (0.03%-0.04%), Al₂O₃ (0.30%-2.79%), (K₂O+Na₂O)(0.07%-1.76%), indicating that Sipingshan gold deposit is formed in a hydrothermal depositional environment related to magmatic activity in the tectonic setting of active continental margins. The granite porphyry is identified as the parent rock of Sipingshan gold deposit, with a U-Pb zircon age of (113.5±0.7) Ma. The H(δD=-182.3‰--84.0‰),O(δ¹⁸O_V-SMOW=6.5‰-14.3‰), and S(δ³⁴S=-12.4‰-29.7‰) isotopic results indicate that the ore-forming fluid is mainly atmospheric precipitation, and the ore-forming materials have stratigraphically dominated multi-source features. To sum up, Sipingshan gold deposit is a hydrothermal sedimentary deposit formed in the Late Yanshanian active continental margin tectonic background. The continuous subduction of the Pacific plate caused large-scale delamination, resulting in a transition from extrusion to extension. This granite porphyry magma formed at this period migrated to the shallow crustal magma chamber to heat the overlying stratum, and formed a temperature and pressure gradient zone in the shallow crust, which prompted the atmospheric precipitation on the surface to enter the stratum along the fissures to form a fluid circulation system, and continuously extract Au elements in the formation to form ore-bearing fluids. In the early stage,when the pressure drived the ore-bearing fluids to be ejected from the surface, it encountered the surface water and cooled rapidly, and the ore-forming materials precipitated rapidly, forming the  layered ore-bearing siliceous rocks and siliceous cemented conglomerates, which formed layered orebodies by metasomatism of the underlying rhyolite porphyry. This process was weakened with the thermal power provided by the magma chamber dying down. In the later stage, the ore-bearing fluids stayed in the fissure channels or penetrated into the fissures of the early consolidated ore-bearing layer, then precipitated to form vein-like and reticulated-vein-like ore bodies.

Key words: Sipingshan gold deposit, mineralization; geochronology, geochemistry, stable isotopes, exhalative sedimentary