Sedimentary Characteristics and Evolution of the Lower Triassic Evaporite and Its Control on the Formation of Potassium Ore in the Puguang Area,Northeastern Sichuan Basin
Sedimentary Characteristics and Evolution of the Lower Triassic Evaporite and Its Control on the Formation of Potassium Ore in the Puguang Area,Northeastern Sichuan Basin
Thick layers of anhydrite and salt are deposited in the Middle and Lower Triassic strata in the Sichuan Basin.The rediscovery and transvaluation of polyhalite associated with salt,which has been called"a new type of polyhalite potassium ore",has brought widespread attention to this mineral in recent years.However,research on this type of polyhalite has focused mainly on the aspects,such as the mineral development characteristics and genetic types,etc.Studies focusing on high-resolution analyses of the sedimentary characteristics and evolution of the surrounding strata and its control on the formation of polyhalite are rare.Therefore,in this study,microfacies and high-precision sequence stratigraphy analyses were carried out using core data of the continuous coring target interval of well CXD1.Fourteen microfacies types were identified and divided into six microfacies associations representing different sedimentary facies zones with different energy and environmental characteristics ranging from restricted to evaporative platform.On this basis,according to the vertical development of microfacies,stratigraphic thickness and typical diagnostic interfaces,four fourth-order sedimentary sequences and multiple fifth-order cycles within them were defined.The results implied that the primary polyhalite associated with salt in the northeast Sichuan Basin was obviously affected and controlled by sea level fluctuations.Specifically,it developed mainly in the superposition period between the end of regressions in the fourth-order sequences and transgressions of the fifth-order cycles.The evaporative condition in the former provided an important basis for the formation of polyhalite;however,the external seawater replenishment provided by the latter was the necessary condition.
关键词
沉积微相/层序地层/沉积控矿/杂卤石/下三叠统/川东北
Key words
microfacies/sequences stratigraphy/sedimentary control on mineralization/polyhalite/Lower Triassic/northeastern Sichuan Basin
维普
万方数据