Late Paleozoic deformation and tectonic significance of the South Central Tianshan Shear Zone, Kawabulake area, East Tianshan, NW China: Constraints from quartz fabrics and geochronologic data

Abstract

The South Central Tianshan Shear Zone occurs along the southern margin of the Central Tianshan Block (CTB), NW China. This shear zone contains important information about the history of the amalgamation of various plates in the southwestern margin of the Central Asian Orogenic Belt. This study focuses on the deformation of the South Central Tianshan Shear Zone within the Kawabulake area in East Tianshan and provides insights into the late Paleozoic tectonic history of this region. Field observations indicate that the shear zone records at least two ductile deformation events (D1 and D2), where D1 is a sinistral strike-slip deformation event and D2 is dextral strike-slip. The shear zone contains four giant tectonic lenses that were formed during the D2 event. Microstructures and quartz crystallographic preferred orientation patterns indicate that D1 and D2 both occurred under low temperature conditions. We constrained the timing of deformation using mica 40Ar/39Ar and zircon U–Pb approaches. The timing of D1 deformation is constrained in the range of 400–290 Ma and the early and late stages of D2 deformation occurred at ca. 290 and 276–270 Ma, respectively. Regional comparisons indicate that D1 resulted from the clockwise rotation of the Tarim Craton and the oblique subduction of the South Tianshan Ocean crust beneath the CTB, the early stage of D2 was the result of the oblique collision between the Tarim Craton and the CTB, and the late stage of D2 records the convergence of the Tarim Craton and plates north of the CTB.