Multistage Enrichment of the Sawafuqi Uranium Deposit: New Insights into Sandstone‐hosted Uranium Deposits in the Intramontane Basins of Tian Shan, China

Abstract

Meso‐Cenozoic intracontinental orogenic processes in the Tian Shan orogenic belt have significant effect on the sandstone‐hosted uranium deposits in the intramontane basins and those adjacent to the orogen. The Sawafuqi uranium deposit, which is located in the South Tian Shan orogenic belt, is investigated to reveal the relationships between uranium mineralization and orogenies. Recent exploration results show that the Sawafuqi uranium deposit has tabular, stratiform, quasi‐stratiform, and lens‐like orebodies and various geological characteristics different from typical interlayer oxidation zone sandstone‐hosted uranium deposits. Systematic studies of ore samples from the Sawafuqi uranium deposit using a variety of techniques, including thin section observation, α‐track radiograph, electron microprobe and scanning electron microscope, suggest that uranium mineralization is closely related to pyrite and organic matter. Mineralization‐related alterations in the host rocks are mainly silicification and argillation including kaolinite, illite (and illite‐smectite mixed layer) and chlorite. Tree stages of mineralization were identified in the Sawafuqi uranium deposit: (i) uranium‐bearing detritus and synsedimentary initial pre‐enrichment; (ii) interlayer oxidization zone uranium mineralization; and (iii) vein‐type uranium mineralization. The synsedimentary uranium pre‐enrichment represents an early uranium enrichment in the Sawafuqi uranium deposit, and interlayer oxidation zone uranium mineralization formed the main orebodies, which are superimposed by the vein‐type uranium mineralization. Combining the results of this study with previous studies on the Meso‐Cenozoic orogenies of South Tian Shan, it is proposed that the synsedimentary uranium pre‐enrichment of the Sawafuqi uranium deposit was caused by Triassic Tian Shan uplift, and the interlayer oxidation zone uranium mineralization occurred during the Eocence‐Oligocene period, when tectonism was relatively quiet, whereas the vein‐type uranium mineralization took place in relation to the strong orogeny of South Tian Shan since Miocene.

Litho‐mineralogy, geochemistry, and chronology for the genesis of the Kamust sandstone‐hosted uranium deposit, Junggar Basin, NW China

“…Widespread pyrites occur within all ore‐bearing sandstone samples, most of which have a microcrystalline, subhedral, colloidal shape, followed by a framboidal shape. The pyrite aggregates mostly exist in dispersed and cement form (Figure 4f,g), indicating a reducing environment for the ores (Goswami, Bhagat, Zakaulla, Kumar, & Rai, 2017; Liu et al, 2017). Scanning electron microscope observation results show that the clay mineral assemblage consists of kaolinite, montmorillonite, chlorite, and illite, with kaolinite as the main component, followed by montmorillonite, with little chlorite and illite content.…”

“…Widespread pyrites occur within all ore-bearing sandstone samples, most of which have a microcrystalline, subhedral, colloidal shape, followed by a framboidal shape. The pyrite aggregates mostly exist in dispersed and cement form (Figure 4f,g), indicating a reducing environment for the ores (Goswami, Bhagat, Zakaulla, Kumar, & Rai, 2017;Liu et al, 2017). Scanning electron microscope observation results…”

“…temperature environment and open system (Bonnetti et al, 2020;Goswami et al, 2017;Jaireth et al, 2016), which may not be related to the deep hydrothermal fluid (Liu et al, 2017;X. Y. Yang et al, 2009).…”

Origin and Role of Kaolinization in Roll-Front Uranium Deposits and Its Response to Ore-Forming Fluids in the Yili Basin, China

“…With respect to the low temperature of kaolinite formation in this study, 18 O (H2O)V-SMOW values were calculated based on the fractionation equation between minerals and water following Savin [47]. As micritic kaolinite is dominant in the extracted kaolinite-dominated clay minerals, it is considered that the O and H isotope data in Table 5 are related to fluid associated with micritic kaolinite formation.…”

“…According to the typical model of alteration and distribution of minerals in roll-front uranium deposits established by Harshman and Adams [15] and DeVoto [16], the kaolinite-rich zone, known as the "white bleaching zone" [17,18], is formed at the limonitic front and is closely associated with uranium mineralization; therefore, it is an effective prospecting indicator for sandstone-hosted uranium deposits [15,19,20]. It has been verified that kaolinization in sandstone-hosted uranium deposits resulted from either local organic matter (OM) or foreign organic matter [21], and it is particularly related to liquid or gaseous OM, such as humic acid and hydrocarbon-aqueous species.…”