Provenance and Paleodepositional Environment of Li-rich Fine-grained Clastic Rocks from Baitianba Formation in the North Margin of Yangtze Block

Key words: 
• Baitianba Formation /
• Lithium-containing fine clastic rocks /
• Provenance analysis /
• Paleoenvironmental condition /
• Lithium enrichment

Abstract: The discovery of lithium mineralized bodies in multiple layers of the Permian-Jurassic layers in the northern margin of the Yangtze Block is of great significance to the investigation, development and utilization of sedimentary lithium resources. In order to clarify the provenance and tectonic setting of the parent rock in the source area of the lithium-bearing fine clastic rocks of the Jurassic Baitianba Formation, and to discuss the control of the paleo-environment on lithium enrichment, the typical lithology of the strata has been studied in detail, and the XRD and elemental geochemistry studies have been carried out. Results: The main element oxide discriminant function and LaN/YbN-ΣREE, K2O-Rb and La/Th-Hf diagrams show that the potential provenance region is a mixed provenance region of emerging medium-acid igneous rocks, sedimentary rocks and metamorphic rocks. The main element oxide discrimination function and the diagrams of La-Th, Ti/Zr-La/Sc, La-Th-Sc, Th-Sc-Zr/10 and Th-Co-Zr/10 show that the tectonic background of the sedimentary period was active continental margin, and some parent rocks in the source area were formed in continental island arc environment. Ga, Sr/Ba, Sr/Cu, C value, CIA, U/Th, Ni/Co and other paleoenvironmental indicators indicate that lithium-containing fine clastic rocks were deposited in a weakly reduction-oxidizing freshwater environment in a warm and humid climate. The A-CN-K and Th/ Sc-Zr /Sc diagram show that the parent rock of the source area has undergone moderate to intense weathering when the debris was first deposited. The comprehensive study shows that paleosalinity and paleoreduction-oxidation conditions control the enrichment of lithium to some extent, but the content of clay minerals in lithium-containing fine clastic rocks is the key to determine the enrichment of lithium. The lithium content level in the source area plays a leading role in lithium enrichment (" source "), and the sedimentary environment affects the lithium content in the formation (" storage ") by influencing the content of clay minerals.