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The Erlian basin, an essential sandstone-type uranium enrichment basin in northern China, is situated in the central segment of the Central Asian Orogenic Belt. In the basin, the Lower Cretaceous Saihan Formation constitutes the most significant uranium-bearing layer. Influenced by tectonic overturning and paleo-valley evolution, provenances experienced intensely spatial and temporal transition, and the precise depositional age of the Saihan Formation remains ambiguous. In this study, we conducted an integrated investigation of the Saihan Formation in the Naomugen Depression, employing petrographic analysis, LA-ICP-MS U-Pb geochronology and trace element geochemistry of detrital zircons. These methodologies are to determine the maximum depositional age, identify provenance characteristics of the uranium-bearing sandstones, and elucidate tectonic implications. Detrital zircon geochronological results reveal three predominant age clusters: 434 Ma (Caledonian), 265 Ma (Variscan), and 140 Ma (Yanshanian), indicating multiple magmatic sources spanning the Paleozoic to the Early Mesozoic. Notably, the youngest single-grain ages (125±3 Ma, 115±6 Ma, 122±2 Ma, 108±2 Ma) and weighted mean ages (113.3 Ma, 123 Ma) collectively constrain the maximum depositional age of the Saihan Formation to (108±2) Ma, corresponding to the Albian stage of the Early Cretaceous. Provenance analysis demonstrates that detrital materials were derived from: Cretaceous exposures in the central-western Sonid Uplift, Weijing intrusions in the Bayinbaolige Uplift, and Caledonian-Variscan complexes in the western Bainaimiao Arc. Integrating with volcanic records from the Tengger Formation, our findings confirm a rapid tectonic uplift event at ～110 Ma during the late Early Cretaceous. This tectonic episode created optimal metallogenic conditions through the formation of structural slopes and thick sandstone sequences, providing critical constraints for uranium exploration models in the region.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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