Provenance Analysis of Lower Jurassic in Dongdao Haizi Sag—Evidence from petrology, elemental geochemistry, and detrital zircon chronology

Key words: 
• Key words: Dongdaohaizi Sag /
• Provenance Analysis /
• detrital zircon /
• tectonic activity

Abstract: Abstract: [Objective] The provenance composition and evolution of the Lower Jurassic Badaowan Formation and Sangonghe Formation in the Dongdaohaizi Sag of the Junggar Basin are of great significance for the early Jurassic tectonic activity of the Karamaili orogenic belt in the provenance area. [Methods] Based on the composition of sandstone clasts, rare earth elements and detrital zircon U-Pb ages, the provenance characteristics and evolution process of the Badaowan Formation and Sangonghe Formation were analyzed. [Results] The results show that the Lower Jurassic sandstone in the study area is dominated by with an average content of 37.7% of rock fragments in thin sections, mainly tuff fragments and basalt fragments, and a small amount of metamorphic rock fragments.The Badaowan Formation shows no obvious differentiation between light (LREE) and heavy rare earth (HREE), while the Sangonghe Formation has the characteristics of slight LREE enrichment and HREE loss, and the age of detrital zircons in the Badaowan Formation mainly falls in the Permian and Devonian periods, while the age data of the Sangonghe Formation is mainly from the Carboniferous period, and there are obvious differences in age composition.[Conclusion] The analysis by synthesis of provenance characteristics, the parent rocks in the Lower Jurassic source area of the Dongdaohaizi Sag are dominated by medium-acid magmatic rocks and mafic magmatic rocks, and the tectonic background is mainly the transitional recycled zone of the recirculating orogenic belt, which is consistent with the mixed source formed by ocean-land subduction in the eastern Karamaili orogenic belt and the Karamaili orogenic belt after the closure of the ocean basin. The provenance of the Badaowan Formation to the Sangonghe Formation in the Dongdaohaizi Sag has undergone a conversion from the main source of oceanic crustal subduction to the closed source of the Carboniferous ocean-land, which has a good response to the increasing uplift process of the Early Jurassic of the Karamaili Orogenic Belt, indicating the continuous uplift and differential denudation process of the Early Jurassic of the Karamaili Orogenic Belt.