Mineralogy and geochemical investigation of Cambrian and Ordovician–Silurian shales in South China: Implication for potential environment pollutions

Abstract

Rapid expansion of shale gas development in China raises environmental and human health concerns. Several studies present related information on these concerns in the United States and Canada, yet they are few in China at present. This paper presents a series of original and published mineralogical and trace elements data from two gas shales (Niutitang shale and Longmaxi shale) considered as producing gas shale in China. Mineralogical and geochemical data surveyed can be applied to evaluate the potential environment pollutions during shale weathering and hydraulic fracturing. After compilations of the mineralogical and trace elements data, we can conclude that (a) there is generally more pyrite compared with carbonate for Niutitang shales, indicating that Niutitang shales are more prone to generate the hydrogen ions than Longmaxi shales; (b) many of the environmental hazardous trace elements considered here show an association with organic matter and/or pyrite, indicating that these trace elements are prone to mobilize and release during shale weathering and hydraulic fracturing; (c) some environmental hazardous elements like As, Ni, and Ba that have extremely high concentrations in some regions as compared with the screening limits for soil and drinking water should attract more attention; and (d) clay‐rich shale with abundant organic matter may be the most favourable shale gas reservoir for the Niutitang shale, especially for those shales in Lower Yangtze region. Moreover, more mineralogical and geochemical data will be required for a comprehensive environmental impacts assessment.