Accumulation mechanism of crust–mantle mixing helium-rich reservoir : a case study of the Subei basin (Eastern China)

Li, Wenqi and Liu, Huichuan and Holland, Greg and Zhou, Zheng and Chen, Jianfa and Li, Jian and Wang, Xiaobo (2024) Accumulation mechanism of crust–mantle mixing helium-rich reservoir : a case study of the Subei basin (Eastern China). International Geology Review. pp. 1-14. ISSN 0020-6814

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Abstract

Helium reservoirs, as an indispensable and scarce strategic resource, can be categorized into two primary origins: crust- and mantle-sourced. Understanding the mechanisms of its formation and accumulation is a crucial challenge in helium exploration. Previous work on helium exploration has mainly focused on crustal helium, while mantle-sourced helium-rich reservoirs have been overlooked. Helium reservoirs with both a crustal and a mantle source exhibit higher helium abundance than that of crustal helium reservoirs and are sporadically distributed in Neogene basins worldwide, but their formation and evolution is poorly understood. In Eastern China, several Neogene basins preserve high quality crust/mantle helium-rich reservoirs, and in this study, we use the Subei Basin as a case study to investigate processes controlling He accumulation and storage. The helium reservoirs can be classified into two types based on the lithological nature of the structural traps: sand reservoir with mud cap and basalt reservoirs with mud cap. The main controlling factors for the formation of crust–mantle helium-rich reservoirs include deep-seated faults, magmatic activity, and mineralization of mantle-derived CO2. Deep-seated faults, along with their associated strike-slip faults, serve as favourable pathways for mantle-derived helium migration and magma upwelling. Magmatic activities serve as the material source for mantle-derived helium as well as the carrier medium in the migration of mantle-derived volatiles. The presence of well-developed sandstone and basalt reservoirs, along with mudstone cap rocks, and the dissolution and mineralization caused by mantle-derived CO2 are important factors in helium accumulation and preservation.