Geochemical characteristics of the Lengjiaxi Group, eastern edge of the Hengyang Basin: provenance, paleoweathering, and tectonic setting

This paper focuses on the Huangxudong Formation-Xiaomuping Formation section of the Lengjiaxi Group in eastern edge of the Hengyang Basin, Hunan Province. Seventeen clastic sedimentary rock samples are collected, and their major elements, trace elements, and rare earth elements contents are tested. Combined with relevant analytical methods and discriminant diagrams, a systematic study is conducted on the provenance composition, paleoweathering intensity, sedimentary environment, and tectonic setting of the Lengjiaxi Group. The results show that the provenance of the Lengjiaxi Group is mainly felsic volcanic rocks, possibly containing a small amount of intermediate-basic volcanic rock materials, and the content of alkaline feldspar in the source area sedimentary parent rocks is low. The source rocks have undergone moderate weathering, and the weathering degree gradually increases from the Huangxudong Formation to the Xiaomuping Formation, which may be affected by later potassic metasomatism. It belongs to bathyal-abyssal turbidite deposits. Different segments of the Huangxudong Formation and the Xiaomuping Formation correspond to the middle fan or outer fan sedimentary environment of the turbidite fan respectively. During the sedimentary period, the climate is warm and humid, and the sedimentary site is near the weak oxidation-weak reduction interface. It is formed in the tectonic setting of an active continental margin. This study provides new geochemical evidence for regional geological evolution.