A Large-Scale Palaeozoic Dextral Ductile Strike-Slip Zone:the Aqqikkudug-Weiya Zone along the Northern Margin of the Central Tianshan Belt,Xinjiang,NW China

The nearly E-W-trending Aqqikkudug-Weiya zone, more than 1000km long and about 30 km wide, is an important segment in the Central Asian tectonicframework. It is distributed along the northern margin of the Central Tianshan belt inXinjiang, NW China and is composed of mylonitized Early Palaeozoic greywacke, volcanicrocks, ophiolitic blocks as a mélange complex, HP/LT-type bleuschist blocks andmylonitized Neoproterozoic schist, gneiss and orthogneiss. Nearly vertical myloniticfoliation and sub-horizontal stretching lineation define its strike-slip feature; variouskinematic indicators, such as asymmetric folds, non-coaxial asymmetric macro- tomicro-structures and C-axis fabrics of quartz grains of mylonites, suggest that it is adextral strike-slip ductile shear zone oriented in a nearly E-W direction characterized by"flower" strusture with thrusting or extruding across the zone toward the twosides and upright folds with gently plunging hinges. The Aqqikkudug-Weiya zone experiencedat least two stages of ductile shear tectonic evolution Early Palaeozoic north vergentthrusting ductile shear and Late Carboniferous-Early Permian strike-slip deformation. Thestrike-slip ductile shear likely took place during Late Palaeozoic time, dated at 269(5 Maby the40Ar/39Ar analysis on neo-muscovites. The strike-slip deformation was followed bythe Hercynian violent S-type granitic magmatism. Geodynamical analysis suggests that thelarge-scale dextral strike-slip ductile shearing is likely the result of intracontinentaladjustment deformation after the collision of the Siberian continental plate towards thenorthern margin of the Tarim continental plate during the Late Carboniferous. TheHimalayan tectonism locally deformed the zone, marked by final uplift, brittle layer-slipand step-type thrust faults, transcurrent faults and E-W-elongated Mesozoic-Cenozoicbasins.