The U-Pb chronologic evidence and sedimentary responses of Silurian tectonic activities at northeastern margin of Tarim Basin

Abstract

U-Pb ages of Devonian detrital zircons from Tabei Uplift have been determined through LA-ICP-MS test technology. The results revealed that most zircon ages concentrate on 460–414 Ma, especially around 436–423 Ma, indicating possible occurrences of strong tectonic events at the northern margin of Tarim Basin during that period. Combined with previous researches on the basin marginal orogenic belts, intense tectonic activities developed at the northeast margin of Tarim Basin and its obvious sedimentary responses in basin during the end of Ordovician to Early-Middle Silurian are discussed. These include (1) several unconformities within the Late Ordovician-Silurian, showing truncation, erosion, and onlap characteristics, which reflected the local uplift formed during the surrounding extrusion process; (2) the Silurian fluvial delta system from northeast to southwest in Keping, Yingmaili, Hade, and Caohu areas, which reflected the partial uplift at the northeast margin and provided clastic supply to basin; and (3) as indicated by heavy mineral analysis, the Silurian sediments came mainly from the recycles of orogenic belts provenance, which indicated the compress tectonic setting. In addition, a wide range of red mudstone layer distribution in the upper part of the Silurian may be closely related to the surrounding tectonic uplift and the rapid decline of sea levels.