东道海子凹陷下侏罗统物源分析及沉积物源响应特征OA

[Objective]Clarifying the provenance composition and evolution of the Lower Jurassic Badaowan Forma-tion and Sangonghe Formation in the Dongdaohaizi Sag,Junggar Basin,has important guiding significance for studies of the sedimentary filling response in this region of the Lower Jurassic.[Methods]A detailed analysis was conducted on the source characteristics and evolutionary processes of the Badaowan Formation and Sangonghe Formation based on the composition of sandstone debris,the geochemical characteristics of whole-rock elements,and U-Pb ages of de-trital zircons.[Results]It was found that the sandstone samples from the Lower Jurassic in the study area were mainly composed of feldspathic lithic sandstone,with an average content of 37.7%of tuff and basalt lithic debris in the thin sections,along with a small amount of metamorphic rock debris.After standardization of shale samples in North America,the Badaowan Formation samples showed no significant differentiation between light and heavy rare earth elements.The Sangonghe Formation exhibited slight enrichment of light rare earths and depletion of heavy rare earths.The age distribution of detrital zircons in the sandstone samples in the Badaowan Formation is mainly concentrated in three ranges:280-330 Ma,400-440 Ma and 490-520 Ma;the Sangonghe Formation is dominated by three peak age ranges:280-350 Ma,380-430 Ma and 460-520 Ma,with similar age compositions.[Conclusions]A comprehensive analysis of provenance characteristics indicated that the Badaowan Formation in the Dongdaohaizi Sag is mainly sourced from the Kela Meili provenance system in the eastern Junggar Basin,and the western Urho and Karamay provenance regions had little influence.During the depositional period of the Sangonghe Formation,the western re-gion began to supply resources,but the eastern Kela Meili provenance system remained the main source of materials in the study area.In the Middle Jurassic,the influence of the western provenance increased,and the Che-Mo paleo-uplift was formed.The Donghaizi Sag was jointly influenced by two major provenance systems.The parent rocks in the Lower Jurassic provenance area of the Dongdaohaizi Sag are mainly intermediate acid magmatic rocks and basic mag-matic rocks,and the provenance is mainly from the transitional and recirculating zones of the recycled orogenic belt.The tectonic setting is dominated by continental island arcs,which is consistent with the mixed-source background formed by oceanic continental subduction around the Junggar Basin,and following closure of the ocean basin.In the context of this tectonic setting,during the sedimentation period of the Badaowan Formation the Dongdaohaizi Sag was influenced by the East Kela Meili source,forming a shallow-water delta lake sedimentary system.Distributary chan-nel sand bodies were extensively developed,but the physical properties were poor,with few favoring hydrocarbon ac-cumulation.During the sedimentation period of the Sangonghe Formation,the Dongdaohaizi Sag was influenced by two major source systems,east and west,and a shallow-water delta lake system developed together with underwater distributary channel microfacies composed mainly of medium and fine sandstones,as well as a small amount of estua-rine dam microfacies with physical properties favorable to hydrocarbon reservoir development.