Thin layers and high-yield dolomite reservoirs were recently discovered in the Permian Guadeloupian Maokou Formation. The genetic mechanism of this reservoir is controversial because of its complex sedimentation and diagenesis in the Maokou Formation. Traditionally, the genesis has focused on sedimentation, karst, and fracture, whereas the influence of the Emeishan mantle plume activity (EMP) has been ignored. In this study, we enumerated petrographic (grouped into micritic bioclastic limestone, limy dolomite, grain dolomite, dolomite cement, calcite cement, and saddle dolomite) and geochemical data (δ¹³C, δ¹⁸O, REE, and ⁸⁷Sr/⁸⁶Sr) from a microscopic perspective to support the impact of EMP on reservoirs. We conclude that EMP activity altered the sedimentary environment and induced a complex diagenesis. The paleogeomorphic reconstruction data indicate that the EMP caused an uplift zone in the NE–SW direction, depositing advantageous high-energy beach facies. In terms of diagenesis, the abnormally high ⁸⁷Sr/⁸⁶Sr ratios and REE with positive Eu anomalies suggest that dolomitization was influenced by both seawater and hydrothermal fluids. Based on the above evidence, we established a reservoir genetic model for the Maokou Formation related to the intensity of the EMP. This study provides a new perspective on the mantle plume activity for the study of carbonate reservoir genesis.

Deeply buried carbonate strata have been recognized as significant exploration targets in recent decades. Great breakthroughs have been found in dolostones of the Lower Cambrian Xiaoerbulake Formation in the northern Tarim Basin, which shed light on global petroleum prospecting in deep Cambrian strata. However, sedimentary architectures of favorable hydrocarbon reservoirs within the Xiaoerbulake Formation remain unclear, hindering further exploration work in this region. In this study, a combination of petrographic, sequence stratigraphic, and C-O-Sr isotopic analysis was conducted for Cambrian dolomites intersected by ultra-deep drill-holes TS5, LT1, and YS2, in order to characterize the depositional architecture of the Xiaoerbulake Formation and infer favorable targets for petroleum exploration. Four high-frequency sequence stratigraphic units are identified within the Xiaoerbulake Formation (SSQ1–SSQ4). The three deep drill-holes occupied different positions within the same progradational depositional system. LT1 was located closest to the rollover and high-energy shoal belt, which contains favorable petroleum reservoirs. The C-O-Sr isotopic ratios, rare earth element distribution patterns and moderate dolomite ordering show that dolomitic reservoirs within the Xiaoerbulake Formation were formed during the early marine/shallow-burial diagenesis and may have been modified by basinal fluids. The outcomes of this study imply that ultra-deep Cambrian strata have the potential to preserve complete prograding carbonate wedge architectures that are favorable for petroleum exploration in the Tarim Basin, and possibly elsewhere in the world.