The Paleo-Asian Ocean controlled the tectonic evolution of Northeast Asia and formed the Karamaili Orogenic Belt in the eastern Junggar basin. However, the chronological constrain of the evolution of the paleo-Karamaili Ocean remains unclear. In this study, we focused on the sandstones of the Lower Jurassic Badaowan and Sangonghe Formations in the Dongdaohaizi Depression, Junggar basin near the Karamaili orogenic belt. After detailed observations and descriptions of the macroscopic features of the sandstone, we obtained information on petrology and geochronology. The Dickinson diagrams indicate that the provenance area had the characteristics of a transitional and recycling provenance, which is a collisional orogenic belt with a background of oceanic-continental subduction. The detrital zircon ages of the Lower Jurassic sediments in the Dongdaohaizi Depression can be divided into three peaks: ~300 Ma, ~420 Ma, and ~510 Ma for Badaowan Formation and ~310 Ma, ~410 Ma, and ~500 Ma for Sangonghe Formation. The youngest detrital zircon age is 241 ± 2 Ma, representing an Early Permian depositional age. Combined with previous studies, the sediments in the study area represent a provenance from the Karamaili Ocean. During the Early Jurassic, the consistent subduction of the residual East Junggar Ocean induced continuous uplift in the Karamaili region, resulting in an increasing exposure of deep-seated rocks to provide sedimentary material. According to the tectonic background of the Junggar region, the results indicate that the Karamaili Ocean, as part of the Paleo-Asian Ocean, experienced three evolutionary stages: Cambrian-Early Silurian (460–540 Ma), Late Silurian-Early Carboniferous (360–440 Ma), and Late Carboniferous–Triassic (240–340 Ma).

The Junggar Basin basement comprises microcontinental blocks amalgamated through successive paleo-oceanic accretion events. Stratigraphic and provenance studies within the basin are crucial for reconstructing its evolution and understanding the closure of paleo-oceanic systems. This study presents an integrated petrographic and geochemical analysis of the Lower Jurassic Badaowan Formation sandstones in the Dongdaohaizi Depression, located in the eastern Junggar Basin. The results reveal a progressive decrease in lithic fragment content and an increase in quartz content from older to younger strata within the Badaowan Formation, indicating an increase in compositional maturity. Provenance analysis indicates that the sandstones are predominantly derived from tuffaceous rocks, granites, basalts, and minor metamorphic rocks. Heavy mineral assemblages, including zircon, chromian spinel, tourmaline, and garnet, suggest parent rocks consisting primarily of intermediate to acidic igneous rocks, mafic igneous rocks, and metamorphic rocks. Integrated petrographic and geochemical data from the surrounding areas of the Dongdaohaizi Depression confirm that the Badaowan Formation sandstones are primarily sourced from the eastern Kelameili Mountain. The continued uplift and migration of the Kelameili Mountain during the Early Jurassic played a dominant role in shaping the sedimentary provenance. LA-ICP-MS analyses reveal that the rare earth element (REE) concentrations in the Lower Jurassic sandstones are slightly lower than the average REE content of the upper continental crust. The sandstones exhibit weak differentiation between light and heavy REEs, reflecting a depositional environment characterized by anoxic reducing conditions. Geochemical results indicate a tectonic setting dominated by a passive continental margin and continental island arc in the source area. Synthesizing these findings with related studies, we propose that the Kelameili Ocean, as part of the Paleo-Asian Ocean, underwent a complex evolution involving multiple oceanic basins and microcontinental subduction–collision systems. From the Middle Ordovician to Late Silurian, the Kelameili region evolved as a passive continental margin. With the onset of subduction during the Middle Devonian to Early Carboniferous, the eastern Junggar Basin transitioned into a continental island arc system. This tectonic transition was likely driven by episodic or bidirectional subduction of the Kelameili Ocean.

The Dashigou deposit is one of the most representative carbonatite-type Mo-REE deposits in the East Qinling metallogenic belt of China, with a molybdenum resource of more than 180 kt and a rare earth resource of 37.8 kt. Recent exploration has revealed a considerable scale of uranium mineralization within this deposit. Therefore, this study conducted detailed mineralogical and EPMA U-Th-Pb chemical dating on the uranium mineralization in the Dashigou deposit. The results indicate that the U-ore body in the Dashigou deposit mainly consists in carbonatite veins, and principally as anhedral, mesh-like uraninite. The mineral assemblage is characterized by uraninite + rutile + bastnasite + parisite or brannerite. The uraninite displays geochemical compositions of high Y and Ce and low Si, Ti, and Mg. The EPMA U-Th-Pb chemical dating is 144 ± 3.1 Ma, representing the Yanshanian uranium mineralization age in the region. The newly discovered uranium mineralization age indicates that the deposit experienced a uranium remobilization event during the Cretaceous and was formed in an intracontinental orogenic and extensional environment post-collision orogeny.