Difference Analysis of Organic Matter Enrichment Mechanisms in Upper Ordovician-Lower Silurian Shale from the Yangtze Region of Southern China and Its Geological Significance in Shale Gas Exploration

Figure 5

Al-Mn-Fe content and origin analysis diagram for the siliceous minerals from the upper Ordovician Wufeng Formation-lower Silurian no. 1 member of the Longmaxi Formation in the X-1 well. The values of excess silicon are nearly all in the biogenic zone, indicating that the excess silicon is derived from biogenesis. The base map is from Wedepohl [20], Adachi et al. [21], and Yamamoto [22]. See Figure 1 for the well location. I: bio-origin; II: hydrothermal origin.