Provenance Analysis of the Silurian Kepingtag Formation in the Northwest Margin of Tarim Basin-Evidence from Petrology and Geochemistry

The integration of petrological and geochemical analyses serves as an effective methodology for reconstructing depositional environments and constraining sediment provenance within distinct tectonic frameworks. This study investigates the provenance characteristics of the Silurian Kepingtag Formation in the northwestern Tarim Basin through an integrated approach combining field outcrop observations and laboratory analyses. Fieldwork covers the Sishichang, Dawangou, and Tongguzibulong sections, while laboratory analyses include clastic component identification, whole-rock major and trace element geochemical analysis, and rare earth element (REE) profiling. These efforts enable a systematic evaluation of sediment sources and their tectonic linkages. The research provides a theoretical basis for understanding the tectono-sedimentary framework of the northwestern Tarim Basin during the Early Silurian and offers significant guidance for reconstructing the lithofacies paleogeographic pattern of the basin during this period. Petrographic analyses reveal a lithological assemblage dominated by lithic quartz sandstones and lithic sandstones, with subordinate feldspathic lithic sandstones. Quartz exhibits secondary overgrowths. In a relatively stable tectonic environment, sediments undergo a gentle burial rate, which favors the formation of this phenomenon. Lithic fragments are dominated by magmatic lithics, indicating that the source contains magmatic rocks. Detrital component analysis reveals that the provenance of Kepingtag Formation sandstones in the study area is predominantly characterized by stable craton and recycled orogenic belt tectonic settings. Integrated geochemical datasets from major element compositions and trace element signatures constrain the provenance characteristics of the Kepingtag Formation sandstones. Major element ratios demonstrate predominant contributions from felsic igneous source rocks, while trace element ratios are diagnostic of sediment derivation from passive continental margin settings, consistent with prolonged tectonic quiescence along the northern Tarim cratonic margin during Silurian deposition The CIA index indicates that the Silurian Kepingtag Formation in the study area exhibits weak to moderate weathering. Integrating the above analyses, the Tabei Uplift—ancient craton setting—is interpreted as the likely provenance source for the sandstones of the Kepingtag Formation in the northwestern Tarim Basin.