The closure time of Junggar Paleozoic oceanic basin: Evidence from Carboniferous detrital zircon U-Pb geochronology in Kalamaili area

The closure time of Junggar Paleozoic oceanic basin is significant for the reconstruction of Paleozoic tectonic framework and evolution of the Central Asian Orogenic Belt (CAOB). The Carboniferous coarse clastic rocks, which are widely distributed in the south of the Kalamaili fault belt, were formed in a fan-delta environment by sedimentary facies analysis. On the basis of regional stratigraphic correlation, rock association characteristics and stratigraphic contact relations, the authors redefined the coarse clastic rocks as the Shanlianglishi Formation. Two profiles of Shanlianglishi Formation from Dishuiquan and Shuangjingzi area, which were respectively located in the western and eastern section of Kalamaili fault belt, were chosen to correlate the stratigraphic sequence. UPb ages of detrital zircons from two coarse sandstone samples on the bottom of Shanlianglishi Formation were measured using the LA-ICP-MS method. The ages of the youngest zircons, 349±4Ma and 355±3Ma, indicate that the sedimentary age of Shanlianglishi Formation were later than 349Ma, and it might have been formed in the early Early Carboniferous. The ages of detrital zircons and the gravel composition show that the provenance of Shanlianglishi Formation was mainly derived from the Devonian volcanic rocks in the north of the Kalamaili fault belt. Integrating the previous data, the authors infer that the coarse clastic rocks formed in the foreland basin were probably the sedimentary response to the uplifting orogenic process of the Kalamaili orogenic belt, and the closure time of Junggar Paleozoic oceanic basin is constrained before the Early Carboniferous.