Zircon SHRIMP U-Pb dating of two linear granite plutons in southern Altay Mountains and its tectonic implications

Abstract：In southern Altay Mountains, some NW-SE striking small linear granite plutons are exposed, which were intruded into Devonian and Early Carboniferous volcano-sedimentary sequences that had undergone intense sinistral ductile shearing. Structural deformation of these granites implies that their intrusion occurred simultaneously with shearing deformation. This paper describes SHRIMP dating data of zircons from two of these granites, namely the southern Altay biotite granite body and the southern Shaerbulake two-mica granite body. Zircons form the southern Shaerbulake intrusive body yield an apparent 206Pb/238U age of (275.1±1.7) Ma, which is interpreted as the intrusive age of the granite pluton, as evidenced by geological, petrological and deformational characteristics of the granite plutons and related zircon CL images. Based on the new dating data, the authors infer that the sinistral ductile shear deformation of Erqis faulted zone and southern Altay Mountains probably occurred posterior to 275 Ma. In combination with available data, this paper deals briefly with the Permian tectonic evolution in southern Altay Mountains.