Types of biogenic quartz and its coupling storage mechanism in organic-rich shales: A case study of the Upper Ordovician Wufeng Formation to Lower Silurian Longmaxi Formation in the Sichuan Basin, SW China

GUAN Quanzhong,DONG Dazhong,ZHANG Hualing,SUN Shasha,ZHANG Surong,GUO Wen

Fig. 3. Energy spectrum analysis of biogenic quartz in Wufeng-Longmaxi Formation shale. (a) Well W202, 2 570.97 m, siliceous shale, with siliceous biological shells composed of type I microcrystalline quartz aggregates, and the red square is the energy spectrum analysis area, SEM; (b) Si element distribution in the red square area of figure (a); (c) O element distribution in the red square area of figure (a); (d) Well W202, 2 570.97 m, "powdered" type II quartz aggregates distributed on organic matter, the red box is the energy spectral analysis area, SEM; (e) Si element distribution in the red square area of figure (d); (f) O element distribution in the red square area of figure (d).