Late Devonian radiolarian-bearing siliceous rocks from the Karamay ophiolitic mélange in western Junggar: Implications for the evolution of the Paleo-Asian Ocean

• Published in: Palaeogeography, palaeoclimatology, palaeoecology palaeoclimatology, palaeoecology, 2016-04, Vol.448, p.266-278
• Main Authors: Zong, Ruiwen, Wang, Zizhang, Jiang, Tao, Gong, Yiming
• Format: Article
• Language: English
• Subjects: Brackish; Late Devonian; Marine; Ophiolitic mélange; Paleo-Asian Ocean; Radiolaria; Radiolarians; Siliceous rocks; Western Junggar
• ISSN: 0031-0182; 1872-616X
• DOI: 10.1016/j.palaeo.2015.10.006

Abundant Late Devonian radiolarians occur in the siliceous rocks of the Karamay ophiolitic mélange in western Junggar. The siliceous rocks are interpreted as deposit in a remnant oceanic basin in view of their petrological and geochemical characteristics. New data suggest that the age of the Karamay ophiolitic mélange can be extended from the Ordovician to Late Devonian, thus representing the youngest known oceanic crust in western Junggar, which indicates that the closure of the Paleo-Asian Ocean was at least after the Late Devonian in southern western Junggar. The Carboniferous formation capping the siliceous rocks units comprises, in ascending order, a broad regressive sequence from the abyssal–bathyal turbidites, littoral-neritic carbonates, and calcareous clastic rocks to molasse, indicating that the ocean–continent transformation probably occurred in the Devonian–Carboniferous transition or the early Early Carboniferous. The oceanic basin was filled with volcaniclastic turbidites in the Visean–Serpukhovian, and evolved into a residual sea basin in the Late Carboniferous. The final closure of the Paleo-Asian Ocean in western Junggar was marked by the emergence of molasse in the late Late Carboniferous. •Radiolarians support the age of the Karamay OM can be extended to the Late Devonian.•Karamay ophiolitic mélange were likely to have formed in the remnant oceanic basin.•Three important ocean–continent transformation periods occurred in western Junggar.•New evolutional model of the PAO was built in western Junggar.•The final closure of the PAO in the late Late Carboniferous in western Junggar