The Paleoproterozoic basin evolution of the Zhongtiao Mountain region in the Trans-North China Orogen, North China Craton

This paper conducted detailed investigations of the lithological assemblages and stratigraphy of the Zhongtiao Group and the Danshanshi Group in Zhongtiao Mountain region, Trans-North China Orogen (NTCO), North China Craton. The Zhongtiao Group comprises of a suit of metamorphic sedimentary rocks, consisting of multicyclic sedimentary rocks composed of clastic rocks, mudstones and carbonate rocks. The geochemical characteristics of the metamorphic sandstone show that the Zhongtiao group experienced a transition from early relative stability to late activity. The age and source characteristics of detrital zircons from the Zhongtiao Group and age of intercalated volcanic rock indicate that they were deposited in a back-arc basin of active continental margin from ~2.1 Ga. The Danshanshi Group is a series of conglomerates and sandstones forming a molasse basin during the collisional orogeny stage at ~1.85 Ga. Taken together, we present a brief scenario for the evolution of the sedimentary basin in Zhongtiao mountain region. From ~2.1 Ga, the eastward-directed subduction of the ocean between western block and eastern block, back-arc basin (Zhongtiao Group) developed behind the arc that located in the west margin of eastern block. At ~1.85 Ga, the ocean between western block and eastern block closed, resulting in the collision of the two blocks along TNCO, the Zhongtiao Back-arc basin underwent fold deformation and resulting in the crustal thickening followed by rapid exhumation/uplift, which shifted the back-arc basin to foreland basins. The Danshanshi molasse basin is formed in foreland basin. Such a shift from the back-arc basins to foreland basins in the Late Paleoproterozoic supports the model that the collision between Eastern and Western blocks occurred at ~1.85 Ga.