Shale gas will be the focus of global oil and gas exploration in the future. As a key mineral component in shale, the characteristics and genesis of feldspar are of great significance for reservoir quality. The feldspar in the Qiongzhusi Formation shale was studied through core observation, X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and major and trace elements analysis. The results show that the content of feldspar in the Qiongzhusi Formation shale is relatively high, with an average content of 27.3%, mainly sodium feldspar. The feldspar presents various forms, such as angular clastic particles and strongly altered particles. It exhibits localized dissolution and illitetization. The feldspar in the Qiongzhusi Formation shale is multi-source, mainly provided by the mixture of felsic sedimentary rocks and granites from the upper crust. The main source areas are the Western Sichuan Block, the Motianling Block, and the Hanyang Block. Rapid sedimentation leading to rapid burial is the primary sedimentary control factor for the high initial content of feldspar in the Qiongzhusi Formation shale. During the late burial and diagenetic stages, localized fluid action, comprising the synergy between micro-scale migration and chemical reactions driven by hydrocarbon generation, acts as a key factor influencing the minor variations in feldspar content. Under a stable tectonic background, the fluids in the Qiongzhusi Formation mainly come from organic acids produced by shale hydrocarbon generation, and the influence of formation water fluids is relatively limited, with a low degree of feldspar mineral transformation.
Zheng et al. (2026) studied this question.