Construction of Thermal-driven Convective Mineralization Model and Exploration Indicators for Qianjiadian Sandstone UraniumOre Field in Songliao Basin

Significant breakthroughs have been made in the exploration of sandstone uranium deposits in the Qianjiadian area of the Songliao basin. The widespread development of basic magma intrusions in the region, along with their increasing relevance to the inherent genetic relationship with uranium mineralization, has attracted growing attention. However, at present, there have been no reports regarding how basic magma intrusion change fluid migration patterns and influence sandstone uranium mineralization. In this paper, the source and migration mechanism of ore-forming hydrothermal fluids and their genetic mechanism for sandstone uranium mineralization under the background of basic magma intrusion were explored through detailed petrographic research, combined with systematic analysis of C-H-O isotope testing of hydrothermal alteration minerals and spatial distribution characteristics of oxidation zones. The results indicate that the ore-forming hydrothermal fluids associated with basic magma intrusion are CO₂-enriched warming formation water originating from atmospheric precipitation, which can interact with sandstone to form hydrothermal alteration mineral assemblages, such as kaolinite, dawsonite, dolomite and uraniferous dolomite. These mineral phases provide direct mineralogical evidence for the involvement of mafic magmatic intrusions in sandstone uranium mineralization processes. A new understanding of the thermal-driven convection migration of the regional oxygen-containing warming formation water originating from the southern edge of the basin and the local oxygen-containing warming formation water originating from ancient uplifts driven by the heat of basic magmatic intrusion was proposed. This process leads to the formation of the unique upper and lower double-layer oxidation zones and uranium mineralization features, which are controlled by both hydrothermal alteration and interlayer oxidation zones. Based on these findings, a new thermal-driven convective mineralization model associated with basic magmatic intrusion for the Qianjiadian sandstone uranium ore field was established, which characterized by thermal-driven convection induced by mafic magmat intrusion, dual recharge from both regional and local groundwater systems, convective migration of heated groundwater, and focused discharge through geologic windows. The model displays that uranium exploration in this area should primarily focus on interlayer oxidation zones, particularly targeting mineralization controlled by either combined or individual effects of regional and local interlayer oxidation processes. This study provides innovative exploration strategies and new directions for sandstone uranium deposits in mafic magma-modified terranes, significantly advancing the theoretical understanding of sandstone uranium mineralization.