Tectonic evolution of the Huangling dome and its control effect on shale gas preservation in the north margin of the Yangtze Block, South China

Significant breakthroughs of shale gas exploration have been made in Lower Cambrian and Sinian shale in the north margin of the Yangtze Block, South China. The drill wells with industrial gas flow located in the southern margin of the Huangling dome. Base on the geological survey, 2D seismic, geochronological and drill wells data, the tectonic evolution history of Huangling dome was studied, and its control effect on the preservation condition of shale gas was discussed. The result shows that the Huangling dome might undergo four tectonic stages: (1) About 800 Ma, granite intrusion in the Huangling dome basement, primarily of granites replaced metamorphism rocks; (2) 800–200 Ma, no significant tectonic movement with slowly buried history; (3) From 200 Ma, multi-phase uplift and the sedimentary rocks was eroded in the core of the Huangling dome. Shale gas in the Cambrian and Sinian strata was well preserved in the margin of the Huangling dome as the following reasons: (1) The Sinian shale was buried about 7.8 km in-depth during Middle Jurassic, source rocks have a suitable thermal maturity for shale gas; (2) The rigid basement of the Huangling dome was mainly composed by homogeneity granite, without intensive deformation. As the main challenges of the widely distributed Lower Cambrian and Sinian shale are high-maturity and intensive deformation, a geological unit with a dome probably is a favorable zone for the old age shale gas. Therefore, it indicates that the adjacent zone of the Xuefengshan, Shennongjia and Hannan are the geological units with a dome and probably have potentials for the exploration of shale in the Lower Cambrian and Sinian.