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BACKGROUND As an epigenetic deposit dominated by supergene fluid, a sandstone type uranium deposit has many low-temperature minerals. In recent years, the Pengyang uranium deposit, a deep sandstone type uranium deposit, has been discovered in the southwest edge of the Ordos Basin, China. The deposit has the characteristics of large sand body scale, wide uranium mineralization area, large thickness and high grade. Many low-temperature altered minerals have developed, including calcite, gypsum, pyrite, and clay minerals. It is of great significance to study the spatial distribution characteristics of minerals and their relationship with uranium minerals to identify the main sources and properties of ore-forming fluids and their controlling on uranium mineralization. Near-infrared core spectral scanning technology can identify layered silicate minerals such as kaolinite, montmorillonite, sericite, and sulfate minerals such as gypsum and alunite, and carbonate minerals such as calcite and dolomite. OBJECTIVES To study the distribution characteristics of minerals and their relationship with uranium mineralization. METHODS Core samples were scanned by VNIR-SWIR spectroscopy core scanning system and analyzed by TSG 8.0. In addition, the microscopic occurrence characteristics of minerals related to uranium minerals were observed by scanning electron microscopy. RESULTS Minerals such as kaolinite, montmorillonite, illite, chlorite, carbonate, gypsum, and iron oxide were identified in the Luohe Formation. The mineral assemblage of uranium ore section was "illite+gypsum+carbonate", and minor kaolinite was present locally. CONCLUSIONS The uranium-bearing section of the Luohe Formation is mainly a set of alkaline environments in the sedimentary period. However, there is also an injection of reducing acid fluid in the metallogenic period.

Abstract: The Yangbishan iron–tungsten deposit in the Shuangyashan area of Heilongjiang Province is located in the center of the Jiamusi Massif in northeastern China. The rare earth element and trace element compositions of the scheelite show that it formed in a reducing environment and inherited the rare earth element features of the ore‐forming fluid. The geochemical characteristics of the gneissic granite associated with the tungsten mineralization show that the magma formed in this reducing environment and originated from the partial melting of metamorphosed shale that contained organic carbon and was enriched with tungsten. In addition, in situ Hf isotopic analysis of zircons from the gneissic granite indicates that they probably originated from the partial melting of a predominantly Paleo–Mesoproterozoic crustal source. According to LA‐ICP‐MS zircon dating, the Yangbishan ore‐related gneissic granite has an Early Paleozoic crystallization age of 520.6 ± 2.8 Ma. This study, together with previous data, indicates that the massifs of northeastern China, including Erguna, Xing'an, Songliao, Jiamusi, and Khanka massifs, belonged to an orogenic belt that existed along the southern margin of the Siberian Craton during the late Pan‐African period. The significant continental movements of this orogeny resulted in widespread magmatic activity in northeastern China from 530 Ma to 470 Ma under a tectonic setting that transitioned from compressional syn‐collision to extensional post‐collision. [ABSTRACT FROM AUTHOR]

The hydrocarbon activity in Pengyang area, situated in the southwestern Ordos Basin, is notably prominent. Investigation on the migration laws of hydrocarbons is imperative for comprehending the involvement in uranium mineralization. Based on the analysis of spatial distribution of hydrocarbon containing fluid and hydrocarbon generation conditions of sandstone in the Luohe Formation, the organic geochemical characteristics including hydrocarbon components, carbon isotopes and biomarker compounds were analysed. The research results indicate that: (1) hydrocarbon fluid activities in the Luohe Formation are predominantly observed in layers exhibiting higher uranium mineralization. The mudstone of the Luohe Formation had low organic matter content and low thermal maturity, which was not conducive to hydrocarbon generation. (2) Hydrocarbon‐containing fluid in the sandstone of Luohe Formation not only contained reducing gases such as methane and hydrogen but also chloroform asphalt components. The carbon isotopes of hydrocarbon in sandstone inform Luohe Formation resemble oil and gas in the Mesozoic. The biomarker parameter inferred that the parent rock of hydrocarbons in the Luohe Formation was formed under reducing and freshwater conditions, and hydrocarbon generation occurred at the mature stage. As above mentioned, a comparison was carried out between the affinity of hydrocarbon‐containing fluid in the Luohe Formation and different layers of hydrocarbon source rocks. The migration behaviour of hydrocarbon‐containing fluid in the Pengyang area has been summarized, and the involvement of hydrocarbon‐containing fluid in uranium mineralization has been discussed. The main concepts are as follows: the sedimentary environment and thermal evolution conditions of hydrocarbons in the sandstone of Luohe Formation resemble those of the primary hydrocarbon source rocks in the Yanchang Formation. The main hydrocarbon charging events in the Luohe Formation occurred before the Late Cretaceous period, which is primarily related to two hydrocarbon generation events from 130 to 100 Ma in the Yanchang Formation and fault conduits connecting the Triassic to the Cretaceous Strata. The hydrocarbon‐containing fluid released from Yanchang Formation migrating to the Luohe Formation provides reducing conditions for the precipitation of uranium in oxygen‐bearing water bodies. [ABSTRACT FROM AUTHOR]