Emeishan mantle plume created 400 km gas-rich carbonate belt in Sichuan Basin

Beneath the modern Sichuan Basin lies a geological masterpiece orchestrated by the Emeishan mantle plume 262 million year ago. A landmark study published in the Journal of Palaeogeography (Chinese Edition) uncovers how plume-driven tectonics shattered a Permian carbonate ramp into a complex platform system, creating a 400-kilometer-long dolostone hydrocarbon reservoir belt now pivotal to China’s energy exploration. Led by Prof. Yuan Haifeng (Chengdu University of Technology) and Dr. Zhang Benjian (PetroChina Southwest Oil and Gas Field Company), the research resolves decades of debate by precisely dating the tectonic-sedimentary pattern transition to 263–262 Ma using conodont biostratigraphy, while also revealing novel exploration targets.

The investigation began by reconciling conflicting sedimentary models for the Middle Permian Maokou Formation. While some researchers advocated a persistent carbonate ramp, others proposed a rimmed carbonate platform. Integrating drill cores (e.g., Well Cheng-20), outcrops (Guangyuan, Huaying), and seismic data, the team established that pre-volcanic crustal uplift—induced by the Emeishan mantle plume—initially shaped a southwest-dipping ramp during ~273–263 Ma (Maokou Members 1–2). Critically, the first appearance of the conodont Jinogondolella altudaensis marks a radical shift: intensified plume activity triggered tectonic-sedimentary differentiation at 263–262 Ma, fracturing the ramp into a fault-controlled platform featuring the Mianzhu-Pengxi intraplatform depression, Guangyuan-Kaijiang shelf, and the colossal Jian’ge-Fengdu platform margin.

This 400-km margin belt became the cradle of hydrocarbon-rich dolostones. As sea levels fluctuated, high-energy shoals frequently emerged, enabling pervasive early dolomitization that preserved porosity—explaining why recent wells (e.g., Jiaotan 1) here yield industrial gas flows exceeding 1 million m³/day. Notably, the plume’s influence extended beyond reservoir formation: the Guangyuan-Kaijiang shelf and Mianzhu-Pengxi depression served as prototypes for Late Permian trough, e.g., the Kaijiang-Liangping trough. Furthermore, the study identifies potential submarine volcanic eruptions in southwestern Sichuan, suggesting a hidden E-W trending intra-platform depression near Dujiangyan-Jianyang.