Neoproterozoic active continental margin in the northwestern Tarim Craton: Clues from Neoproterozoic (meta)sedimentary rocks in the Wushi area, northwest China

Abstract

The blueschist-bearing Aksu Group and the associated rocks in the Aksu–Wushi area play a crucial role in understanding Neoproterozoic tectonic evolution of the Tarim Craton. However, the age and tectonic setting of the Aksu Group, and its relationship with the Qiaoenbrak Formation, remain controversial. Previous studies were mainly focused on the well-known Aksu Group from the Aksu area, but little attention has been paid to the equivalent rocks from the Wushi area. In this paper, we present the first detrital zircon LA-ICP-MS U–Pb ages for the Aksu Group metasedimentary rocks from the Wushi area, and we also measure U–Pb ages for detrital zircons from the Qiaoenbrak Formation to figure out its affinity to the Aksu Group. Our data show that the protolith of the metasedimentary rocks of the Aksu Group from the Wushi area was deposited between ca. 790 and 761 Ma, which was earlier than that from the Aksu area ( > ca. 750 Ma). The Qiaoenbrak Formation was deposited between ca. 780 and 744 Ma, probably contemporaneous with or earlier than the metasedimentary rocks of the Aksu Group. Geochemical data for the metasedimentary rocks of the Aksu Group from the Wushi area suggest that they were deposited in an arc-related setting. Combining the detrital zircon age spectra and geochemistry analyses, we propose that the sedimentary rocks of the Aksu Group and the Qiaoenbrak Formation were probably deposited in a similar tectonic setting related to an active continental margin in the northern margin of the Tarim Craton. The Aksu blueschists and the associated Neoproterozoic arc were probably related to the circum-Rodinia subduction system, rather than assembly of the Rodinia or Gondwana in the interior of the supercontinents.