Pattern and spatiotemporal evolution of the Middle Jurassic provenance system in central Sichuan Basin
The Middle Jurassic Shaximiao Formation in central Sichuan Basin is an important tight gas exploration battlefield in China,and its provenance system and source rocks are complex and variable,which restricts the subsequent oil and gas exploration to a certain extent.Based on the analysis of detrital components,elemental geochemistry,and zircon clastic composition of each sub-member of the Shaximiao Formation,the debris content,source rock properties,and structural setting of the Shaximiao Formation are investigated to explore the controlling effects of source rocks and tectonesm of orogenic belt on the provenance system.The results show that the Shaximiao Formation in the western part of central Sichuan Basin has greatly varying single-crystal quartz content,and significant change in the compositional maturity of the sandstone in the plane and vertical direction;in the northwestern part,which rests in an integrated tectonic environment with island arcs,mixed orogenic belts,and collisional orogenic belts,the source rocks are mainly upper crustal felsic rocks and intermediate-acid mixed igneous rocks,the tectonic setting is dominated by continental island arcs,as well as active continental margins,which presents a high coupling to the Shaximiao Formation source rocks in the northern part;a high coupling is also found between the southwestern part and the western Sichuan Basin and southern section of Longmen Mountain;and the zircon age spectrum of the Shaximiao Formation in the eastern part is well coupled with that in eastern Sichuan Basin.During J2s1 and J2s21,the northern part of central Sichuan Basin formed the primary pattern of long-axis material supply as a result of Daba Mountain reverse thrust,while the southwestern part of central Sichuan Basin experienced short-axis transport from the southern section of Longmen Mountain.During J2s22 and J2s23,the strong over thrusting of Daba Mountain caused the entire central Sichuan Basin to be filled with long-axis distal deposits.During J2ss24,the thrusting in the northern section of Longmen Mountain provided material supply to the northwestern part of central Sichuan Basin,but the main part of central Sichuan Basin was dominated by the Daba Mountain province system.The study results provide a theoretical reference for reconstructing the paleogeography and predicting favorable sand bodies in the Middle Jurassic in the Sichuan Basin.
Central Sichuan BasinMiddle Jurassic Shaximiao FormationClastic analysisElemental chemical analysisTectonismProvenance analysis
万方数据
维普
