Early Paleozoic Tectonic Evolution of the Chinese Southwest Tianshan Orogen: Implications from Detrital Zircon U-Pb Geochronology of the Biedieli Sedimentary Rocks, Northern Wushi Area, NW China

Abstract

The Southwest Tianshan is the suture zone between the Central Tianshan and the Tarim Craton. To better illustrate the subduction polarity of the Southwest Tianshan Ocean, a systematic detrital zircon LA-ICP-MS U-Pb geochronology of sedimentary rocks of the Devonian Apadaerkang Formation and the Carboniferous Akeqiayi Group of the Biedieli area in the Wushi region is the focus. Detrital zircon ages indicate that the youngest grains of the targeted quartz sandstones are Late Devonian and Early Carboniferous in age, respectively. These ages also have relatively similar age spectra, indicating a similar tectonic setting and source in the Biedieli area during the Devonian to Carboniferous. The main spectrum peaks occur at 2360, 1960, 810, 640 and 440 Ma, with a principal age peak in the early Paleozoic (474–430 Ma), and the Central Tianshan Terrane is indicated as the main source. The detrital zircon geochronology and sedimentary characteristics of the Biedieli rocks indicate that the Paleozoic sedimentary rocks in the northern Wushi region were formed at an active continental margin, associated mainly with the early Paleozoic subduction of the South Tianshan Ocean.