关键词: 铀成矿, 辉绿岩, 热液改造, 流体包裹体, 松辽盆地南部

Abstract:  In recent years, large and medium-size uranium deposits such as Qianjiadian, Baolongshan and many uranium minings have been discovered through uranium exploration in the southern Songliao basin. Diabase is widely developed in the uranium ore concentration area, mainly distributed around the uranium deposit, near the oxidation fronts of Yaojia Formation, exhibits a spatial correlation with uranium mineralization. While the relationship between diabase and uranium mineralization remains debated, core observation, microscopic identification, and fluid inclusion analysis suggest a significant hydrothermal influence of diabase on uranium mineralization. The microscopic identification shows brannerite formed at a higher temperature and metasomatized the early ilmenite, filling along the fissures, and co-existing with automorphic pyrite, revealing that the formation of uranium deposits in southern Songliao basin may be superimposed on the factors of late magmatic hydrothermal activity. Fluid inclusion studies yield an average temperature of 115.7 ℃, characterizing the ore fluid as low-temperature hydrothermal, exceeding the temperature of uranium-containing oxygen-containing fluids (24.5  ℃) in Yaojia Formation oxidation zone. The inclusion salinity distribution shows low, medium, and high salinity areas (three intervels), representing three distinct fluid activity periods. Combining the existing chronology, geochemistry and exploration results, the uranium mineralization in the southern Songliao basin is divided into four stages: primary preconcentration (96.0-87.0 Ma), uranium-containing and oxygenated water infiltration mineralization (67.0-53.0 Ma), hydrothermal superimposition and reworking (43.0-37.0 Ma), and interlayer oxidation continuous superimposition (17.0-0.7 Ma). Notably, the  hydrothermal superimposition period (43.0-37.0 Ma) coincides with the major intrusion age (49.4-39.1 Ma) of diabase.

Key words:  , uranium mineralization, diabase, hydrothermal transformation, fluid inclusions, southern Songliao basin