Fig.1 (a) Regional map of the Jishou steep slope zone of Xiangxi, and (b) cross-section along line B-B' acrossing well XJD1 (locations of line B-B' and well XJD1 see Fig.1a). Modified after [14].

Fig.2 A composite diagram showing the lithology, depth variation of TOC content and fluid inclusion sampling sites in well XJD1

Fig.3 Photos of the Niutitang Formation core specimens from well XJD1 showing mineral-bearing veins

Fig.4 Photomicrographs and cathodoluminescence images showing the petrographic characteristics of vein-filling minerals from the Niutitang Formation of well XJD1

Fig.5 Relationship between δ18O and δ13C for calcite veins of the Niutitang Formation of well XJD1

Fig.6 Laser Raman spectrum of primary methane inclusion in calcite veins of the Niutitang Formation of well XJD1 (methane peak at 2 907.96 cm-1)

Fig.7 Photomicrographs showing the petrologic characteristics of fluid inclusions from the Niutitang Formation of well XJD1

Fig.8 Histogram of homogenization temperatures of fluid inclusions from the Niutitang Formation of well XJD1

Fig.9 Diagram of homogenization temperatures and burial history for determination of events and ages of fluid activity in well XJD1 in Xiangxi area (burial history from [14])

Fig.10 Diagram of homogenization temperatures and burial history for determination of trapping ages of hydrocarbon related inclusions in Xiangxi area (burial history from [14])

Fig.11 A schematic illustration of shale gas formation process in the study area