**Author details**

**Figure 12.** The pore volume percentages for shale samples.

60 Tectonics - Problems of Regional Settings

rather than because of their undeformation. Ross and Bustin suggested that shales enriched in both clays and organics have the largest micropore volumes, suggesting a micropore contribution from both the organic and clay fractions. In the present study, the shale sample of D3, which is poor in clay and TOC, has the least micro- and mesopores. Kareem et al. found that the clay minerals are over-represented at the pore surfaces and in pore spaces compared to the other major minerals such as quartz and feldspar [56]. The knowledge of effective mineralogy complicated the influence of clay minerals on the pore structure. The biogenic quartz produced by precipitation during diagenesis with silica is derived from graptolite and radiolarians [57], which may also control the pore volume and structure in shales. This type of quartz affects microporosity significantly and has certain correlation to TOC content. There are no clearly defined relationships between quartz mineralogy and pore structure, because the micropore characteristics of the samples did not change with the quartz content in this study. Furthermore, the parts of extra quartz content in fracture filling of deformed shale may come from the hydrothermal source, after the tectonic deformation and fracture generations. The relationship between shale compositions and pore structure is not well reflected in the change of shale pore structure in deformed shale samples for the present study. There is no significant difference in organic matter content in deformed and undeformed samples, which agrees with a similar microporosity on all of the samples. Allscale pore structure analysis reveals that the deformed shale had notable higher macropores percentages than undeformed shale. At the same time, the total porosity and micropores were constant, suggesting that the evolution of pore structure in structural deformed shale was due to part of mesopores was disappeared due to compression of the tectonic stress,

and macropores were generated due to the development of microcracks.

A series of comb-like folds and trough-like folds in eastern Sichuan Basin were the deformation controlled by multilayer detachment, which is different from the typical Jura type

**6. Conclusions**

Mingliang Liang, Zongxiu Wang\*, Linyan Zhang, Huijun Li, Wanli Gao and Chunlin Li

\*Address all correspondence to: wangzongxiu@sohu.com

Institute of Geomechanics, Key Lab of Shale Oil and Gas Geological Survey, Chinese Academy of Geological Sciences, Beijing, China
