Abstract: The Harlik Range is located in the northeastern part of the Tianshan Orogenic Belt and resulted from subduction of the Paleo-Asian Ocean and arc-continent or arc-arc accretionary orogeny. The Harlik metamorphic belt occurs at the southern foot of the Harlik Range and comprises high-grade metamorphic rocks and migmatites. Until now, the timing and genesis of migmatites are poorly studied. In this study, we conducted field structural investigations and LA-ICP-MS zircon U-Pb dating for the migmatites. The results show that the migmatites were likely derived from partial melting of high-grade meta-sedimentary rocks of the Harlik metamorphic belt. Numerous leucocratic dykes and in-source leucosome were deformed in various degrees and yielded consistent zircon U-Pb ages of 332-330 Ma. Considering the syn-kinematic characteristics of the in-source leucosome, it can be proposed that the migmatization and deformation of the Harlik metamorphic belt occurred in ca. 330 Ma. Combining the previous studies on the metamorphic rocks and nearby plutonic rocks and taking the regional tectonic evolution into account, we suggest that the Harlik area probably underwent a post-orogenic setting since 330 Ma. The migmatites were likely formed by decompression partial melting and occurred as part of the basement of the Harlik arc, exhumation and uplifting of which might be related to the emplacement of the coeval post-collisional plutons.

Key words: Eastern Tianshan Orogen, Harlik Range, late Paleozoic, migmatites, post-collisional extension, zircon U-Pb age